Magnum® Steel Push PierTM Technical

Transcription

Magnum Piering, Inc.
Magnum® Steel Push PierTM
Technical Reference Guide
May 10, 2004
© Copyright 2002-04 Magnum Piering, Inc. All Rights Reserved.
No portion of this document may be copied or reproduced in any
manner whatsoever without written approval from Magnum Piering, Inc.
Magnum® Steel Push PieringTM
Technical Reference Guide
TABLE OF CONTENTS
Introduction
Introduction Letter
Magnum Products
Applications
Foundation Repair
Guide Specifications
Geotechnical Report
Inspection
Case Study
Engineering
Axial Capacity
Bracket Eccentricity
Anchor Bolts
Specifications
Pier Capacity
Bracket Spacing
Product Drawings
Testing
Bracket Strength
Pier Shaft Strength
MAGNUM® STEEL PUSH PIER™
TECHNICAL REFERENCE GUIDE
Introduction
by Howard A. Perko, Ph.D., P.E.
Consulting Engineer for Magnum Piering, Inc.
Push pier is the trade name used in conjunction with the hydraulically-jacked,
steel pipe micropile. Although Magnum steel push piers and other similar
systems have been used to underpin and repair existing structures throughout the
United States for over 50 years, very few engineers and architects are familiar
with their capabilities and applications. This is due in part to the general lack of
technical information available on the subject of push piering.
The Magnum Steel Push Pier Technical Reference Guide was developed
specifically for architects, geotechnical engineers, structural engineers, and
building officials. It contains considerable details regarding the axial and lateral
capacity, connection to structures, installation procedures, design, and
specification of hydraulically-jacked steel push piers. Sample details, plans,
reports, inspections, and specifications are included. The purpose of this guide is
to provide the background knowledge necessary to not only ascertain when steel
push piers are an appropriate foundation repair alternative but also to enable the
composition of a detailed performance specification.
As will be discussed in more detail herein, one of the advantages of steel push
piering is that by virtue of the method of installation a full-scale load test is
performed at every pier location, and capacity can be verified to a high degree of
accuracy. Almost all push piers are installed using the weight of the structure to
provide the necessary force to drive the pier. A significant advantage of Magnum
steel push piers is that they are installed using the foundation bracket to transfer
the weight of the structure to the pier, and hence the integrity of the structure, the
connection of the bracket to the structure, and the mechanical strength of the
bracket are all tested during proof loading of Magnum steel push piers.
Thank you for your interest in Magnum steel push piering.
Howard A. Perko, Ph.D., P.E.
ABBREVIATED CURRICULUM VITAE OF
HOWARD A. PERKO, Ph.D., P.E.
EDUCATION
Ph.D. Geotechnical Engineering, May 2002, Colorado State University
M.S. Geotechnical Engineering, May 1996, Colorado State University
B.S. Civil/Mining Engineering, May 1993, Michigan Technological University
PROFESSIONAL ENGINEERING REGISTRATION
Colorado (No. 33340)
Ohio (No. E-66008)
Wisconsin (No. 35955)
West Virginia (No. 15378)
Minnesota (No. 43042)
Kentucky (No. 22128)
New York (No. 081365)
Florida (No. 61051)
Georgia (Pending)
SELECT WORK EXPERIENCE
2000 to
Present
Engineering Consultant, Magnum Piering, Inc., Cincinnati, OH
1998 to
Present
Principal Engineer, Secure Foundations, Inc., Fort Collins, CO
1994-1998
Project Engineer, CTL/Thompson, Inc., Denver, CO
Exclusive helix pier and steel push pier foundation consultant for Magnum Piering, Inc. Manage
telephone technical support center for foundation installation contractors. Coordinate on-going
product development and product testing activities. Developed plans and specifications for
manufactured foundation components. Authored product technical support documents.
Founder and majority owner of a consulting structural engineering firm that specializes in design
of new foundations and foundation repair plans. The firm currently employs 11 engineers,
technicians, and support staff, and has completed over 500 projects ranging from light residential
to low-rise commercial buildings. (www.secureengineer.com)
Planned and supervised geotechnical field investigations and materials testing programs and wrote
soil and foundation reports. Project experience includes several structures supported by helix
foundations, small to large zoned earth dams, ski areas, underground garages and tanks,
pavements, utilities, and commercial and residential structures. Performed one of the first helix
foundation inspections in Colorado.
SELECT PUBLICATIONS
Perko, H.A. (2003). “Lateral Capacity and Buckling Resistance of Helix Pier Foundations”, Foundations
Technology Seminar – Helical Foundations and Tie-Backs, Deep Foundations Institute, Helical Pile Committee,
University of Cincinnati, Cincinnati, OH
Perko, H.A. (2000). “Energy Method for Predicting the Installation Torque of Helical Foundations and Anchors”,
New Technologies and Design Developments in Deep Foundations, N.D. Dennis, Jr., R. Casteli, and M.W. O’Neill,
Eds., ASCE Press, Reston, VA, pp. 342-352.
PATENTS
Earth Anchors and Methods for their Use, U.S. Patent No. 6,058,662.
Helice Pier Post and Method of Installation, U.S. Patent No. 6,722,821
SELECT AWARDS
NASA Graduate Student Research Fellowship, Jet Propulsion Laboratory, 1999-2002
First Place Technical Paper, Graduate Division, AIAA Regional Conf., Albuquerque, NM, 1996
Initiation to Chi Epsilon, Civil Engineering Honor Society, Houghton, MI, 1992
SELECT MEMBERSHIPS
Associate Member, American Society of Civil Engineers
Member, Deep Foundation Institute Helical Pile Committee
Inductee, Order of the Engineer
Magnum Steel Push Piering Products
About Magnum Piering
Magnum Piering, Inc. was founded in 1985 by Mr. Donald
Rippe, Sr. in St. Louis, MO. Mr. Rippe invented the
Magnum® Plate Bracket for which he received a U.S. Patent
in 1989. The Magnum® Plate Bracket is a key component
of a steel push piering system known as the Magnum® Steel
Push Piering System. Also, Mr. Rippe invented and received a patent for the Magnum® Slab Jack System, which
is used to lift sunken concrete slabs. These two product lines,
along with other piering products, are all manufactured at
Magnum’s manufacturing plant and are distributed nationwide through a network of Authorized Magnum Piering
Dealer/Installers.
Mr. Brian Dwyer, owner of Dwyer Companies, purchased
Magnum Piering, Inc. in April of 2000 and relocated all
Magnum operations to the company’s corporate headquarters
in West Chester, OH. Dwyer Concrete Lifting, another
subsidiary of Dwyer Companies, is the Authorized Magnum
Piering Dealer/Installer for Ohio, Indiana and Kentucky.
The Magnum® Steel Push Piering system is recognized in
the industry as one of the most efficient and cost effective
underpinning systems for use in stabilizing and lifting residential and light commercial structures.
Also, each of Magnum’s Authorized Dealer/Installers are
required to complete the Magnum Piering Authorized Dealer
Certification Program. The combination of this comprehensive training program and Magnum’s engineering and field
support, provides an unequalled level of technical proficiency
within the steel push piering industry.
Magnum® Steel Push Piering products are manufactured at
Magnum’s headquarters in West Chester, Ohio using only the
finest high-grade steel and welding materials. Magnum’s
commitment to superior product quality is unparalleled in the
industry. When you specify Magnum® Steel Push Piering
products, you will have confidence knowing you have specified the very best.
Unless You Tell Them . . .
Clients & General Contractors are Going to
Think All Steel Push Pier Systems are the Same
•
Time Tested - Installations Since 1987
•
Guaranteed Load Testing for Each Pier Installed
•
Engineering Reference Manual & Support
•
Most Efficient System on the Market
•
Calibrated Hydraulic Ram Program
•
Patented Plate Bracket or Angle Brackets
•
Dealer Certification & Training
•
Highest Capacity for Lowest Cost Per Pier
•
Dealer/Installers Coast-to-Coast
•
Case Study Library
At Magnum Piering, we take great pride in our push piering
products, and our commitment to engineering and technical
support is unequalled in the industry.
When You Specify Magnum Steel Push Piers,
. . . You’re Specifying the Very Best!
Pier Sections
•
36 Inch Length
•
3 Inch O.D.
•
Mechanical steel tube with minimal
tensile & yield strength of 50,000 PSI
•
Steel Specification ASTM A-513
Available In
•
1/8” Wall Thickness
•
1/4” Wall Thickness
•
Optional Hot-Dip Galvanize
Foundation Brackets
Magnum Plate Bracket
U.S. Patent #5,234,287
Bracket Specifications
•
Bracket Tube Wall 3.875 in. O.D.
•
Bracket Tube ASTM A-519 Grade 1026
•
70,000 # Minimum Tensile Strength
•
60,000 # Minimum Yield Strength
•
Bracket Plate ASTM A-36 Hot Rolled Steel
•
3600 # Minimum Yield
Magnum Angle Bracket
The Company & Support Behind the Products
By having registered geotechnical engineers and structural
engineers on staff, Magnum
Piering takes its commitment
to engineering and technical
support very seriously. The
company periodically hosts
engineering seminars including load tests and field demonstrations with the company’s steel piering systems.
In addition to distributing
technical reference manuals,
the company also makes
project case history information available to engineers,
architects and general
contractors.
Magnum Piering - where
engineering and technical
support are part of our
everyday life.
EXAMPLE SPECIFICATIONS
FOR
STEEL PUSH PIER INSTALLATION
EXAMPLE SPECIFICATIONS
FOR STEEL PUSH PIER INSTALLATION
1.
SCOPE
This item pertains to the installation of steel push piers at the locations shown on the
Plans or staked by the Owner or General Contractor. These specifications and the Plans shall
be used in conjunction with a standard contract to procure the work.
2.
ACCESS
Owner will provide for right of entry of Push Pier Foundation Contractor, all
necessary personnel, and equipment for conducting the steel push pier installation work.
Push Pier Foundation Contractor will remove and replace any structures, utilities, pavements,
landscaping and other improvements in the work area to facilitate steel push pier installation.
Reasonable care shall be exercised by Push Pier Foundation Contractor to avoid damage to
existing structures, utilities, pavements, landscaping and other improvements during the
course of the steel push pier installation work.
3.
UTILITIES
Owner or General Contractor will locate all underground structures and utilities. Any
such underground structures and utilities in and nearby areas of the steel push pier
installations will be clearly marked prior to steel push pier installation work. No steel push
pier shall be installed at a horizontal distance from a utility or underground structure if the
horizontal distance is equal to or less than half the depth of the utility.
4.
SAFETY
In accordance with generally accepted construction practices, the Push Pier
Foundation Contractor shall conduct construction operations in such a manner as to assure
maximum safety of persons and property in the immediate vicinity of steel push pier
installation work. Push Pier Foundation Contractor shall provide and utilize safety clothing
and equipment in accordance with General Contractor’s safety plan and OSHA Standards.
5.
INSURANCE
The Push Pier Foundation Contractor shall obtain and maintain general liability
insurance to the limits described in the Owner’s contract and adequate Worker Compensation
Insurance as prescribed by the Worker’s Compensation Act. This insurance shall cover all
of the Push Pier Foundation Contractor’s personnel on site at anytime.
© Copyright 2002 Magnum Piering, Inc. All Rights Reserved
(may be copied for use in construction specifications)
6.
CAPACITY
Loads shown on the Plans are design allowable loads. These loads shall include dead
loads and live loads of an existing structure as determined by a licensed professional
engineer. Live loads shall include snow, wind, and earthquake forces as well as other
applicable forces. Push pier spacing shall be such that the design capacity of the push piers
are capable of supporting the total load of the structure. In areas of soft soils or fill, downdrag of soils against push piers should be added to the total load on the piers. A Minimum
Factor of Safety of 1.5 should be used to determine the required ultimate capacity of the steel
push piers with regard to their interaction with soil and bedrock. The Push Pier Installation
Contractor shall install all piers to the required ultimate capacity at each pier location.
The capacity of a push pier and bracket used to underpin an existing structure is as
much a function of the strength of the concrete in the existing structure as it is a function of
the pier and bracket capacity. Application of lateral load and overturning moment to an
existing structure through the process of underpinning is an unavoidable consequence of any
underpinning system. The Push Piering Contractor and the Structural Engineer must
evaluate the condition of an existing structure in the field to estimate the load that can be
applied safely to an existing structure without causing additional distress. The Push Piering
Contractor’s method of steel push pier installation must include a means for directly testing
the connection of the bracket to the structure for field verification.
If push piers are installed in areas of expansive soils or where other tensile loads are
applied, the grouting, placement of reinforcing bar within the pier, and/or welding should be
considered as per the Plans.
7.
MATERIALS
All steel push pier materials including the bracket, installation rams, and pier shaft
shall be manufactured by Magnum Piering, Inc. or an equivalent. Steel push piers shall be
3" O.D. round shaft and shall have the required pipe wall thickness so as to prevent buckling
during installation. The potential for buckling is often evidenced by spring-back of the pier
shaft after removing the applied installation load. Spring-back is the slight upward
movement of the pier in a direction opposite the direction of installation. Push piers shall
be installed with a minimum of observable spring-back. If buckling or spring-back is
observed, steel push piers shall be filled with concrete grout. In severe corrosive soils, steel
push piers shall be protected from corrosion by hot-dip galvanizing per ASTM A153 or shall
be filled with concrete grout.
The steel push pier shaft may be required to resist lateral loads in addition to
buckling loads as shown on the Plans. The pier shaft and connection between the pier
foundation and the structure shall resist lateral loads as specified by the Structural Engineer.
The push pier shaft and connections shall have a minimum structural section modulus and
the steel shall have a minimum tensile strength as specified on the Plans. The maximum
section modulus for typical steel push piers is 1.37 in3 and common tensile strength is 70 ksi.
Push pier connections shall consist of in-line, rigid inner sleeves.
8.
INSTALLATION
Each steel push pier shall be advanced into the ground by application of axial force
using a single calibrated installation ram pressing directly against the top of the pier. When
forward advancement of a push pier is halted by soil resistance, the force exerted by the ram
indicates the ultimate capacity of the push pier. Forward advancement of a push pier shall
be considered halted when the movement rate is less than 1/16 inch per hour. The Push Pier
Foundation Contractor shall install push piers and demonstrate that movement is halted at
a load equal to or greater than the required ultimate capacity at each pier location as predetermined by the engineer and as shown on the Plans.
The Push Pier Foundation Contractor shall annually calibrate each hydraulic ram used
to determine design capacity of push piers. Current ram calibration information shall be
supplied to the Foundation Inspector upon request.
9.
MODIFICATIONS
Field welding, if required, shall be in accordance with the “Code for Welding in
Building Construction” of the American Welding Society. Welding of galvanized steel can
produce toxic gases and should be done in adequate ventilation and with adequate gas
detection, breathing gear, and other safety equipment. Modification of manufactured push
pier pipe, brackets, and connectors is prohibited and shall not be performed without first
consulting Magnum Piering, other manufacturer, or the Structural Engineer.
10.
INSPECTION
Installation of steel push piers shall be observed by a representative Inspector of a
professional Soils or Structural Engineering firm to verify final depth and installation loads.
The Push Pier Foundation Contractor shall notify Inspector at least 24 hours prior to
installation work. The Inspector shall observe the installations and document the Push Pier
Foundation Contractor’s method and materials used. The Inspector shall maintain a record
of depth and ram pressure readings. The Push Pier Foundation Contractor shall provide the
Inspector with recent calibration information for the rams used to measure capacity.
11.
DRAINAGE
The General Contractor shall provide proper site drainage in the area of all installed
steel push piers at all times during and after construction. Proper site drainage shall conduct
surface water runoff away from the structure and steel push piers. If expansive soils are a
concern, irrigation systems shall not discharge within five (5) feet of an installed steel push
pier.
12.
CLEANLINESS
Immediately upon completion of the work, the Push Pier Foundation Contractor shall
remove any and all equipment, tools, building materials, rubbish, unused materials, concrete
forms, and other like materials belonging to him or used under his direction. Also during the
work, the site occupied by the Push Pier Foundation Contractor and his material stockpiles
shall be kept in a reasonable state of order and cleanliness.
STATE DEPARTMENT OF TRANSPORTATION EXAMPLE SPECIFICATIONS
SECTION 551
STEEL PUSH PIERS
DESCRIPTION
551.01 This work pertains to furnishing and installing steel push piers (a.k.a. hydraulically driven pipe micro-piles
or resistance pier foundations) shown in the Contract in accordance with the Drawings and these specifications.
Each steel push pier shall be installed and load tested at the location and to the elevation, minimum length, and
design allowable load shown on the Plans or as established. These specifications are to be used in conjunction with
State Department of Transportation Standard Specifications for Road and Bridge Construction.
MATERIALS
551.02 Guarantees and Insurance
Steel push pier and bracket manufacturer shall furnish a guarantee for a period of ten (10) years from date of
delivery against defects due to manufacturing of steel push pier and bracket. Steel push pier and bracket
manufacturer must carry product liability insurance. Refer to General Conditions for additional insurance
requirements.
551.03 Prequalification Requirements
Due to the special requirements for design and manufacture of steel push piers, and the requirements for proper
performance of the structural system, as a whole, steel push piers and brackets shall be obtained from an
organization specializing in the design and manufacture of steel push piers. The following manufacturers’ products
are prequalified for use on this project:
A request for using any other manufactured steel push pier products desired for use on this project must be
submitted to the Project Manager and Foundation Engineer for review not less that seven (7) calendar days prior to
the bid date. The request must include:
1.
2.
3.
4.
A catalog or recent brochure describing the manufacturer.
Evidence showing manufacturer has at least five (5) years experience in this area of work.
Detailed descriptions, schematic details, and material properties for all products to be used on this project.
Current ICCES/BOCA/ICBO product acceptance report or complete description of product testing and
manufacturing quality assurance programs used to assess and maintain product quality.
Prior to bidding by any installer using a manufactured steel push pier system that is not prequalified, written
approval to bid must be received from the Project Manager upon consultation with the Foundation Engineer. Project
Manager shall grant approval based on compliance with specific criteria herein. The Project Manager’s decision is
final.
551.04 Minimum Material Requirements
Steel push piers shall have a minimum 3" O.D. round shaft and shall have the required shaft wall thickness so as to
prevent buckling during installation. The potential for buckling is often evidenced by spring-back of the pier shaft
after removing the applied installation load. Steel push piers shall have sufficient diameter and thickness to
minimize observable spring-back. Steel push piers and brackets shall be protected from corrosion by hot-dip
galvanizing per ASTM A123. Steel push pier connections shall consist of in-line, straight and rigid inner sleeves.
The steel push pier bracket shall have a maximum eccentricity (distance between the face of the bracket and the
center of the steel push pier) of 2” or that acceptable to the Foundation Engineer. The connection between the steel
push pier shaft and the bracket and between the bracket and the structure shall have sufficient strength to support
design allowable loads shown on the Plans times a minimum factor of safety of 1.5.
551-1
MATERIAL SELECTION
552.05 Design and Application
A list of all steel push pier and bracket materials to be used on this project shall be submitted with the bid package.
The list shall clearly state the allowable mechanical capacity of all materials. The list shall be certified by the
manufacturer’s engineer. It is the steel push pier installation contractor’s responsibility to select the appropriate size
and type of steel push pier and bracket and design the connection of the bracket to the structure. These
specifications and the Plans provide minimum requirements to aid the contractor in making appropriate materials
selections. The size and type of steel push pier must be such that the steel push piers achieve the appropriate
capacity in the soils at this site within the minimum and maximum length requirements. Failure to achieve proper
capacity shall result in contractor replacing steel push piers as appropriate to support the required loads. All
installation procedures, materials, and replacements shall be acceptable to Foundation Engineer.
CONSTRUCTION REQUIREMENTS
551.06 Warranty and Insurance
Steel push pier installation contractor shall furnish a warranty for a period of ten (10) years from date of installation
against defects due to workmanship on installation of steel push pier and bracket. Steel push pier installer must
carry general liability insurance. Refer to General Conditions for additional insurance requirements.
551.07 Prequalification Requirements
Due to the special requirements for installation of steel push piers, and the requirements for proper performance of
the structural system, as a whole, steel push piers and brackets shall be installed by an organization specializing in
the installation of steel push piers. The following installation contractors are prequalified for work on this project:
Dwyer Concrete Lifting, Inc. - Cincinnati, OH
Earth Tech, Inc. - Land O' Lakes, FL
Extreme Technology's, Inc. - Atlanta, GA
Camden Construction Co. - Pierceton, IN
Concrete Slabjacking - Jessup, MD
Lipe Brothers Construction - Duluth, MN
Pelton Concrete Services - Lake Oswego, OR
Terratec, Inc. - West Columbia, SC
Agate Foundations - Knoxville, TN
Advanced Builders, Inc. - Chesapeake, VA
Marco Concrete Lifting - St. Albans, WV
Pier Tech, Inc. - Maspeth, NY
VSI Geotec, LLC - Lancaster, NY
Any other contractor desiring to bid as the steel push pier installer for this project shall submit a request to the
Project Manager and Foundation Engineer for review not less than seven (7) calendar days prior to the bid date. The
request must include:
1.
2.
3.
A recent company brochure indicating experience in this type of work.
Evidence of having installed steel push piers on at least ten (10) projects, including project name, location,
and client contact information.
Proposed method of installation/ load testing pier and bracket.
Prior to bidding by any installer that is not prequalified, written approval to bid must be received from the Project
Manager upon consultation with the Foundation Engineer. Project Manager shall grant approval based on
compliance with specific criteria herein. The Project Manager’s decision is final.
551.08 Installation Equipment
Each steel steel push pier shall be advanced into the ground by application of axial force using a hydraulic ram(s)
pressing directly against the pier. Installation equipment shall include a direct means of determining the installation
load being applied to the steel push pier and a means for testing both the capacity of the bracket and connection of
551-2
the bracket to the structure. Acceptable methods of load measurement include calibration of hydraulic ram pressure
with axial force, a calibrated mechanical or electronic load cell, or other means acceptable to the Foundation
Engineer. Current evidence of load calibration for Contractor’s equipment shall be provided upon request of
Engineer.
If installation equipment does not include a direct means of testing the capacity of the bracket and connection of the
bracket to the structure, then Contractor shall submit to Foundation Engineer for acceptance detailed drawings of the
proposed bracket and connection of bracket to structurestamped by a professional engineer registered in the State
where the project is located. Drawings shall clearly indicate allowable load capacity.
551.09 Equipment and Material Acceptance
All steel push pier installation equipment and materials shall be acceptable to the Foundation Engineer prior to
delivery to the site. Acceptance will be based upon submission of records and data requested by the Foundation
Engineer, as discussed in Sections 551.02 through 551.08. Once accepted, changes in installation equipment and
materials will not be permitted without additional acceptance, and will be considered only after Contractor has
submitted any and all information requested by Foundation Engineer.
551.10 Installing Steel push Piers
Loads shown on the Plans are design allowable loads. A minimum factor of safety of 1.5 shall be used to determine
the required minimum final installation force for the steel push piers. Contractor shall install and test all piers to the
required final installation force at each pier location.
Steel push piers shall be installed vertically. Steel push piers may be out-of-plumb a maximum of 5% of the final
installation length as measured by observation of the inside of the steel push pier upon completion.
Steel push pier brackets shall be installed at the locations shown on the Plans. Tolerances for bracket placement
shall be 2” in both directions parallel with the face of the bracket and ½” in a direction perpendicular with the face
of the bracket unless otherwise specified.
Steel push piers shall be installed to a final length appropriate to achieve the required final installation force. The
minimum length of the steel push piers shall be such that the pier tip is at approximately the same or lower elevation
as the surface of bedrock shown on the graphic logs of exploratory borings contained in the soil report.
Installation of steel push piers and brackets used to underpin an existing structure is typically performed utilizing the
dead weight of the existing structure as the reaction force necessary to insert the piers into the ground. As such,
steel push pier installation relies upon the strength of the concrete and reinforcing steel in the existing structure.
Application of axial load, lateral load, and overturning moment to an existing structure through the process of
underpinning is an unavoidable consequence of any underpinning system. The Contractor must evaluate the
condition of an existing structure in the field and estimate the maximum installation load that can be applied safely
to an existing structure without causing additional distress. The maximum installation load shall also not exceed
that acceptable by the Foundation Engineer.
551.11 Axial Load Capacity Testing
An axial load capacity test shall be performed at each pier location. The load capacity test shall consist of
application of an axial force to each pier equal to or exceeding the required final installation force and monitoring
pier advancement rate for a minimum of 30 minutes. The test shall be deemed successful provided steel push pier
advancement under the applied load is less than 1/16 inch per hour. Forward advancement of steel push piers shall
be continued until a successful load capacity test has been completed at each steel push pier location.
In addition to the axial capacity of each steel push pier, each bracket and the connection of each bracket to the
existing structure shall be tested during or after steel push pier installation. These capacity tests shall consist of
applying an upward force equal to or exceeding the required final installation force on the steel push pier to the pier
bracket in its final configuration and connection with the existing structure. If the Contractor’s installation
equipment is incapable of performing these capacity tests, then Contractor shall submit a detailed drawing of the
551-3
pier bracket and connection of the bracket to the existing structure that clearly indicates the allowable capacity of the
system in accordance with 551.08.
551.12 Field Modifications
Field welding, if required, shall be in accordance with the “Code for Welding in Building Construction” of the
American Welding Society. Welding of galvanized steel can produce toxic gases and should be done in adequate
ventilation and with appropriate gas detection, breathing gear, and other safety equipment per OSHA regulations.
Modification of manufactured steel push pier shaft, brackets, and connectors is prohibited and shall not be
performed without approval of product manufacturing company and acceptance of Foundation Engineer.
551.13 Quality Assurance Observation
Installation of steel push piers shall be observed by Foundation Engineer or Foundation Engineer’s
representative/agent to verify the length and required final installation loads. Contractor shall notify Foundation
Engineer or Foundation Engineer’s representative/agent at least 24 hours prior to installation work.
METHOD OF MEASUREMENT
551.14 Steel push piers will be measured on a per unit basis with one unit equal to the equipment, materials,
including bracket and pier shaft, and labor required for proper installation and testing of one single steel push pier at
the required final installation capacity, location, elevation, and minimum length specified.
BASIS OF PAYMENT
551.15 The accepted quantities will be paid for at the unit price per unit of measurement for each of the pay items
listed below that appear in the bid schedule. Payment will be made under:
Pay Item
Pay Unit
Steel push Pier & Bracket, Installed
Each
Compensation will not be made for any additional length required to achieve the final installation force that is
beyond the specified minimum length. It is the Contractor’s responsibility to anticipate the required length of the
steel push piers and include these costs in the bid price per unit.
551-4
EXAMPLE GEOTECHNICAL ENGINEERING REPORT
PREPARED FOR:
British Cablevision
Subsurface Investigation
1414 Ash Drive
Columbus, Ohio
ABC Project 51-5121
ABC ENGINEERING, INC
CONSULTING ENGINEERS
Thomas K. Showblock
612 Cherokee Road
Chillicothe, Ohio 45601
ATTENTION: Mr. Thomas K. Showblock, P.E.
REFERENCE: Subsurface Investigation
British Cablevision
1414 Ash Drive
Columbus, Ohio
August 20, 1991
ABC Project 51-5121
Dear Mr. Showblock:
Pursuant to your request, ABC Engineering, Inc. has performed a subsurface investigation at the
above referenced project. Two (2) engineering test borings, designated as B-1 and B-2, were
drilled at the locations shown on the enclosed plan sheet. The test borings were drilled to a depth
of 29.5 feet in B-1 and 30.0 feet in B-2.
Drilling, sampling, field and laboratory testing have been performed in accordance with standard
geotechnical engineering practices and current ASTM D-1452 and D-1586 procedures. Results
from all field and laboratory tests are shown on the enclosed boring logs.
Surface elevations of the test borings were obtained and referenced to elevation 762.50 feet,
being finish floor elevation of existing building.
A.
PROJECT DESCRIPTION
The site is located to the east of Frebis Avenue and Ash Drive intersection, in the City of
Columbus, Ohio.
This investigation is meant for evaluating the subsurface condition beneath the existing office
and studio building.
British Cablevision
1414 Ash Drive
Columbus, Ohio
August 20, 1991
ABC Project 51-5121
Page 2
B.
FINDINGS
Visual inspection revealed that the site is relatively flat with grass ground cover. The existing
building walls, paved areas and sidewalks exhibit some cracking and construction joints
separation.
The test borings exhibited 1.0 to 2.0 inches of topsoil over approximately 23 feet of random fill.
The fill contains slag, wood, plastic glass, metal and brick fragments in clayey silt or sandy silt
matrices. Boring B-1 encountered large wood blocks between 8.0 and 23.5 feet. Strong organic
odor was noted in both borings. Loss on Ignition testing indicated that the fill contains high
organic matters.
The native soil was encountered at an average depth of 23.3 feet below ground surface elevation.
The native soil is described as dark gray changing to brown clayey silt to sandy silt containing
varying amounts of roots and organic matter. A layer of cohesionless soil consisting of sand and
gravel was encountered at an average depth of 27.5 feet in both borings.
Standard penetration blowcounts varied widely throughout the test borings. Blowcounts were
generally affected by stiffness and type of the encountered materials (metal, rotten wood, soil,
etc). Blowcounts, however, ranged from 9 to 96 blows per foot (bpf). Blowcounts in excess of
50 bpf are due to striking on brick fragments, stiff wood or coarse gravel.
Groundwater was encountered at a depth of 22.5 feet in both borings. At completion of drilling
program, test boring B-1 was caved-in at 19.0 feet, and B-2 was caved-in at 27.4 feet with water
level reading at 20.4 feet.
C.
CONCLUSION
Based upon fill/soil data obtained from the drilling and testing program, the following
conclusions have been made:
1.
The existing structure is built over random fill (landfill).
British Cablevision
1414 Ash Drive
Columbus, Ohio
August 20, 1991
ABC Project 51-5121
Page 3
D.
2.
The cracks and separation showing over the existing structure are due to
progressive settlement of existing fill.
3.
Total and differential settlements cannot be estimated due to the variability of fill
composition.
4.
Settlements of subsoil/fill may be due to or a combination of organic matter
decaying, building loading, and/or re-orientation of fill/soil particles with passage
of time.
RECOMMENDATIONS
Due to the considerable depth of the landfill material encountered by the borings and the high
probability of continued movement, we recommend complete underpinning of the existing
structure with a deep foundation system. Based on our experience in the central and southern
Ohio areas, hydraulically jacked steel pipe micropiles (a.k.a. steel push piers) are typically the
most economical deep underpinning method. Listed below are our standard recommendations
for these systems:
Push Piering Systems
1.
Push piers should extend through the existing fill and, hence, must have a
minimum depth of at least 30 feet. Push piers shall have a center-to-center
spacing of not less than 2 feet.
2.
The required design load capacity for the existing perimeter spread footing should
be determined by a licensed professional engineer. He/she should work with the
piering contractor to determine required pier spacing and design loads.
3.
The hydraulic ram used to load the pier shall be fitted with a pressure gauge, shall
be capable of delivering the prescribed loads with a sensitivity of at least 2% of
the required ultimate capacity of the pier, and shall be calibrated at least annually.
The bracket and ram assembly shall be such that loads are applied vertically and
directly to the central longitudinal axis of the push pier with a minimum of
eccentric loading.
British Cablevision
1414 Ash Drive
Columbus, Ohio
August 20, 1991
ABC Project 51-5121
Page 4
4.
After each pier is installed, a proof load shall be applied to the pier using the
calibrated hydraulic ram and pressure gauge. The proof load shall be at least
150% of the required design load and shall be maintained for a minimum of 1 hr
and until the rate of pier advancement in the soil is not greater than 1/16 in/h.
5.
Push pier advancement relative to a fixed frame of reference shall be measured
optically or through the use of a dial gage.
6.
Push piers shall be supplied by Magnum Piering, Inc. or equivalent. Push pier
installation should be observed by a representative of ABC Engineering to verify
proof loading procedures. Field records shall be prepared that at least contain pier
location, applied loads, load duration, and final pier depth.
7.
After all piers have been installed and proof loaded, the structure shall be lifted
and restored to its original grade or to the extent possible without compromising
the structural integrity of the building.
ABC Engineering’s assignment does not include, nor does this geotechnical report address the
environmental aspects of this particular site. We appreciate the opportunity to be of service to
you on this project. If you require any additional information, please do not hesitate to contact
our office.
Respectfully submitted,
ABC ENGINEERING, INC.
Tom Jones, P.E.
Project Engineer
J. S. Edwards, M. S., P. E
Project Engineer
TJ/JSE/bab
Enclosures
APPENDIX A
BORING LOGS
BORING LOG # B-1
CLIENT: Thomas Showblock
PROJECT: British Cablevision
ABC Project No.: 51-5121
Page 1
of
2
Date: 7-20-91
STATION:
Type of Boring: SFA
OFFSET:
Elevation: 762.3'
Drilled By: IC & BC
GROUND WATER: Encountered at 22.5' at Completion Caved in @ 19.0' VOLUME: Heavy
U.C. - Unconfined Compression, psf
* Hand Penetrometer
E le v .
Ft
SAM PLE
No
T o p s o il
x
B lo w C o u n ts
S o il D e s c rip tio n
D e p th
1
6 in
M .C .
%
D e n s ity
PCF
U .C @ %
s tra in s in - in .
2"
B ro w n , D ry, H a rd , S a n d y S ilt
x
a n d F in e to C o a rs e G ra v e l,
x
N
2
2 1 -2 1 -
S o m e B ric k F ra g m e n ts , S o m e
7 5 9 .8
25
46
4
5 -7 -7
14
11
1 1 2 .2
16
31
13
1 1 8 .7 8 ,5 0 0 *
4 -6 -3
9
27
4 -4 -7
11
34
R o o ts (F IL L )
3
x
B ro w n , D a m p , S tiff, C L A Y E Y
2 x
4
S A N D Y S IL T , w ith F in e to
x
C o a rs e G ra ve l (F IL L )
7 5 6 .9
5 .4 '
5
x
6
1 4 -1 5 -
3 x
B ro w n to D a rk B ro w n , D a m p ,
x
7
C o m p a c t, S IL T Y S A N D Y w ith
M e ta l F ra g m e n ts , S la g (F IL L )
7 5 4 .3
8 .0 '
8
x
9
4 x
x
10
11
1 2 D a rk G ra y , D a m p , W o o d w ith
P la s tic B ric k , w ith T ra c e s
1 3 o f C L A Y E Y S IL T (F IL L )
x
14
5 x
x
15
16
17
18
x
19
6 x
4 -5 0 /1 "
x 20
C o n tin u e d o n n e xt p a g e
19
BORING LOG #B-1
CLIENT:
Thomas Showblock
Continue Page
2
of
2
U.C - Unconfined Compression
* Hand Penetrometer
Elev.
Ft
SAMPLE
No
Blow Counts
Soil Description
Depth
6 in
N
M.C.
%
Density
U.C @ %
PCF
strains in - in.
21 Same as above ------------(FILL)
22
23
738.8
23.5'
8,650 @
x 24
7 x
Dark Gray, Damp, Stiff
x 25
4-4-8
CLAYEY SILT with Some
26
27
27.0'
28 Gray, Wet, Very Compact,
SILTY SANDY and Fine to
x 29
732.8
8 x
Coarse Gravel with Some
Organics
29.5'
BOTTOM OF BORING
73
11.50%
91.7
9,150 @
6%
Organics
735.3
12
93.7
32-50/
5"
BORING LOG # B-2
CLIENT: Thomas Showblock
Page 1
of
2
Date: 7-20-91
STATION:
Type of Boring: HSA
OFFSET:
Elevation: 762.5'
Drilled By: IC & BC
GROUND WATER: Encountered at 22.5' at Completion Caved in @ 27.4' VOLUME: Heavy
U.C. - Unconfined Compression, psf
* Hand Penetrometer
E lev.
Ft
SAMPLE
No
B low C ounts
S oil D escriptio n
D e pth
6 in
T opsoil
x
1
M .C .
%
D e nsity
PCF
1"
B rown, D ry to D am p, V e ry H a rd
x
S A N D Y S ILT, with S om e F in e
x
N
2
16-32-
C o arse G ravel, S and stone
760
F ragm ents (F ILL)
34
66
8
122 .3
9-14-16
30
16
109 .6
9-18-11
29
16
124 .1
2-3-6
9
22
122 .3
5-5-5
10
46
5-6-1 3
19
28
2.5'
3
x
B rown, D am p, V ery S tiff, C LA Y E Y
2 x
4
S A N D Y S ILT w ith Little F ine
x
to C oarse G ravel (F ILL)
5
756 .3
x
6
6.2'
3 x
B rown G ray, D a m p, V ery S tiff,
x
7
C L A Y E Y S A N D Y S ILT with
Little F ine to C oarse G ra vel
8.4'
8 with R oot Fiber (F ill)
754 .1
x
9
4 x
x
10
11
12
13
D a rk G ra y, D am p M ed iu m
x
14
D e nse to D ense, C LA Y E Y
5 x
x
S A N D Y S ILT w ith B rick, W ood
15
F ragm ents (F ILL)
16 O dor from A u ger C utting s
17
18
x
19
6 x
x 20
C o ntinued on next p age
U .C @ %
stra in s in - in.
BORING LOG #B-2
CLIENT:
Thomas Showblock
Continue Page
2
of
2
U.C - Unconfined Compression
* Hand Penetrometer
Elev.
Ft
SAMPLE
No
Blow Counts
Soil Description
Depth
6 in
N
M.C.
%
Density
PCF
U.C @ %
strains in - in.
21 Same as above ------------22 (FILL)
739.5
23
23.0'
Dark Gray, Moist, Stiff
x 24
738
SILTY CLAY with Roots
7 x
24.5' 5-6-9
15
36
25
13
x 25
Brown, CLAYEY SANDY SILT
26
27
734.5
28
28.0'
Gray, Wet, Dense, SILTY SAND
x 29
8 x
and Fine to Coarse Gravel
with Wood
x 30
8-12-13
30.0'
BOTTOM OF BORING
115.6
3,000*
APPENDIX B
TEST RESULTS
ABC ENGINEERING, INC.
SOILS DIVISION
LOSS ON IGNITION TEST DATA
PROJECT NO. :
51-5121
DATE:
LAB CODE:
British Cablevision
TECHNICIAN:
T.B #
SAMPLE
08-15-91
ME
PERCENT LOSS BY IGNITION
B-1
1
2
4
5
6
7
8
11
14
17
15
17
18
14
B-2
1
2
16
9
Unconfined Compression Test #1
10
9
8
Load (Thousands)
7
6
5
4
3
2
1
0
0
2
4
6
8
Strain
10
12
14
Stress-Strain Curve
Boring No.1 Sample No.7 Depth 23.5'-25'
Unit Weight - 93.7 pcf
16
Unconfined Compression Test #2
10
9
8
Load (Thousands)
7
6
5
4
3
2
1
0
0
1
2
3
4
5
Strain
6
7
8
9
Stress-Strain Curve
Boring No.1 Sample No.7 Depth 23.5'-25'
Unit Weight - 93.7 pcf
10
APPENDIX C
SITE PLAN
GENERAL PROCEDURES FOR OBSERVATION
OF STEEL PUSH PIER INSTALLATION
As a general rule, all Magnum Piering installation contractors keep a log of installation pressures
as a function of steel push pier depths. In addition, Magnum Piering encourages the observation
of steel push pier installation by the engineer of record or engineer’s representative for additional
quality assurance. This document contains general guidelines for use by the engineering
inspector during steel push pier installation observation.
Capacity Determination
Each Magnum steel push pier is advanced into the ground by application of axial force using a
single Magnum installation ram pressing directly against the top of the pier. When forward
advancement of a steel push pier is halted by soil resistance, the force exerted by the ram
indicates the ultimate capacity of the steel push pier. It is the policy of Magnum Piering that
forward advancement of a steel push pier shall be considered halted when the movement rate is
less than 1/16th inch per hour.
Allowable or design capacity of a Magnum steel push pier shall be determined by application of
a factor of safety. A factor of safety of 3.0 is commonly used in bearing capacity calculations for
footing and drilled caisson foundations. However, when the foundation installation process
includes a direct or indirect measurement of soil strength at the foundation depth, lower factors
of safety are permissible. A traditional example of this is pile driving. The American Society of
Civil Engineers Publication 20_96, “Standard Guidelines for Design and Installation of Pile
Foundations”, explains that a factor of safety of 1.5 is acceptable for pile foundations. Since the
force of a ram on a steel push pier provides a direct test of the capacity of the steel push pier, a
lower factor of safety is permissible for determining design capacity. Magnum Piering
recommends determination of steel push pier design capacity by dividing the ultimate capacity by
a factor of safety of 1.5.
Input Hydraulic Pressure
The hydraulic pressure measured at the input to Magnum installation rams is an indication of the
force exerted on steel push piers and consequently their design capacity. This force can be
approximated by multiplying the hydraulic pressure by the surface area of the ram piston. Since
this calculation does not account for friction of the piston within the ram housing, wear on the
ram surface, and pressure losses through hoses and fittings, a better indication of applied force
may be obtained by physically calibrating each hydraulic ram. It shall be the policy of Magnum
dealer/installers to annually calibrate each hydraulic ram used to determine design capacity of
-1-
steel push piers. In this manner, Magnum dealer/installers will be able to provide clients with
current calibration information regarding their equipment. This information will enable accurate
determination of steel push pier ultimate and design capacity. Magnum steel push pier
installation rams are calibrated by quality assurance technicians at Magnum headquarters in West
Chester, OH. A tag containing an identification number, date of calibration, calibration constant,
and technician initials is typically affixed to each ram.
Connection to Structures
The capacity of a steel push pier and bracket used to underpin an existing structure is as much a
function of the strength of the concrete in the existing structure as it is a function of the pier and
bracket capacity. Application of lateral load and overturning moment to an existing structure
through the process of underpinning is an unavoidable consequence of any underpinning system.
Magnum dealer/installers evaluate the condition of an existing structure in the field to estimate
the load that can be applied safely to an existing structure without causing distress. Installation
of Magnum steel push piers by directly pushing against a structure provides a field verification
that the bracket and connection to the structure can resist the ultimate load applied to the pier.
Application of a factor of safety of 1.5, as described previously, also safeguards against failure of
the bracket and connection to the structure. The engineering representative or inspector should
be aware that other steel push pier systems do not necessarily test the connection of the pier to
the structure during installation because the rams used by others often incorporate additional
fasteners to the structure that are removed with the ram.
Pier Spacing
It is recommended by Magnum Piering that the dead loads and live loads of an existing structure
be determined by a licensed professional engineer whenever possible. Live loads shall include
snow, wind, and earthquake forces as well as other applicable forces. Push pier spacing shall be
such that the design capacity of the steel push piers are capable of supporting the total load of the
structure. In areas of soft soils or fill, down-drag of soils against steel push piers should be added
to the total load on the piers.
Plumbness
Magnum Piering advocates that the orientation of each steel push pier be checked for plumb by
the engineering inspector. This can generally be accomplished visually by the use of re-directed
sunlight from a mirror, an artificial light source, or a laser pointer. The final depth should also be
checked using a plumb bob or steel tape extended down the center of the pier pipe to ensure that
the it was not damaged and that the length was not altered during installation.
-2-
Safety
As with all other hydraulic systems, there exists the constant danger of failure of hydraulic hoses
and fittings. The engineering inspector shall wear safety glasses and other appropriate safety
equipment when observing steel push pier installation. He/she should keep clear of hydraulic
equipment during the inspection to the extent possible.
Record Keeping
For each job, the engineering inspector shall record steel push pier locations and center-to-center
spacing clearly on a plan view of the structure. The date of each installation, weather conditions,
contractor’s representative, steel push pier manufacturing company, steel push pier section
dimensions and other pertinent information shall be recorded at the start of each project.
Installation time, hydraulic pressure, and the corresponding load on the pier should be recorded at
a minimum of 3-foot depth intervals. The final depth of each pier, final installation pressure and
load, total installation time, and rate of pier advancement shall be recorded at the end of each pier
installation. An example steel push pier installation log is attached and may be copied for use by
the steel push pier engineering inspector on Magnum Piering projects.
-3-
STEEL PUSH PIER INSTALLATION OBSERVATION RECORD
Inspector: ____________________________
Date: ______________________________
Project: ______________________________
Location: ___________________________
Contractor: ___________________________
Manufacturer: _______________________
Weather Conditions: ____________________________________________________________
Pier O.D.: ________ Pier Wall Thickness: ____________ Steel Type: ___________________
Bracket Dimensions: ________________ No. & Type of Anchors: _______________________
Plan View of the Structure & Pier Locations
N
Comments: ___________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
STEEL PUSH PIER INSTALLATION OBSERVATION RECORD
Page _____ of _____
Installation Logs:
Pier No.
Depth
Pier No.
Load
Time
Depth
Pier No.
Load
Time
Depth
Pier No.
Load
Time
Depth
Load
Final Installation Values:
Depth
Depth
Depth
Depth
Applied Load
Applied Load
Applied Load
Applied Load
Design Load
Design Load
Design Load
Design Load
Install Rate
Install Rate
Install Rate
Install Rate
Time
Shopping Mall Store Construction Project:
A Steel Push Pier Underpinning Case Study
by Howard Perko, Bill Bonekemper, Dave Jacob and Brian Dwyer
Magnum Piering, Inc., West Chester, Ohio
March 18, 2003
Abstract
Hydraulically driven steel push piers were used for the lifting and stabilization of
two walls of a partially constructed department store located in a shopping mall in West
Chester, OH. Both the north and south walls experienced similar settlement and outward
rotation problems, and significant failures occurred in the concrete floor slabs near the
base of each wall. The soil conditions on the site predominantly consist of glacial till
overlying shale with very shallow ground water. Due to limitations of lot lines, the
original foundation design for the new structure consisted of eccentrically loaded spread
footings. Hydraulically driven steel push piers were installed at the outside edge of the
spread footings along the masonry walls. The piers were driven to refusal at an average
depth of 13.5 feet. Once all piers were in place, the installation contractor systematically
manipulated the hydraulic driving rams to achieve the necessary degree of lift at specific
locations along each wall. As a result of vertical lifting, the tops of both walls were
successfully rotated to near plumb while, at the same time, the vertical deflections were
significantly reduced and brought to well within tolerances defined for the project.
Contained herein is a chronology of events, push pier installation data, a detailed
description of the repair, and information pertaining to building loads and soil
conditions.
Introduction
the two men explained to Dave that there
was a serious foundation failure on the
north and south walls of this 120,000 sq.
foot store. The problem was described
to Dave as critical because all steel
roofing and steel structural work had
been shut down.
After this brief
introductory meeting, the three men
went to view the problems with the
walls. Photographs of the site before
repair are shown in Figs. 1 and 2. As
can be seen in the figures, the store was
in the early stages of construction.
Concrete masonry unit (CMU) block
walls had been constructed and were
temporarily braced for wind loads. The
Dave Jacob, Dwyer Concrete
Lifting’s Ohio Regional Manager,
received a phone call from the GC’s
Construction Project Manager on the
afternoon of October 14th. The manager
asked Dave if he would come to the
construction site at the mall to look at
settlement problems with two masonry
block walls that were part of a new
department store currently under
construction. Dave met with both the
GC and the construction manager for the
department store’s regional construction
manager for the mid-eastern district, and
-1-
line, the design was changed and instead
the first approximately 250 feet of the
wall’s footing was shifted inward and
constructed flush with the exterior
alignment of the CMU block wall. This
change in the foundation design, in
conjunction with heavy amounts of rain
at the site for several days, were deemed,
by GC’s structural engineers and the
contracted geotechnical firm for the
project, to be the sources of the failure.
roof trusses were not completely in place
at the time of the failure.
The first wall that the owner, the
construction manager, and Dwyer’s
Dave Jacob visited was the north wall –
the wall with the most severe problem.
A considerable crack in the interior
concrete slab was immediately apparent,
and it measured approximately 1/2" to
5/8" wide at its worst point. The crack
ran adjacent to the wall for
approximately 200 feet and ranged in
distance from 3 to 4 feet from the wall’s
base. The two men quickly pointed to
some hand written measurements
marked at eye level on the wall about
every 20 feet. As they explained to
Dave, these markings represented the
distance the north wall had rolled
outward (to the north) at the top of its 27
foot height as measured by the steel
contractor on October 10th.
The
measurements ranged from a minimum
of 1/8", close to both the west and east
corners of the wall, to a maximum of 23/4”, near the center of the wall’s 310foot total length.
The extreme amount of lateral
wall movement had created two serious
situations for the contractor and owner.
Fig. 1 North Wall of Store
Under Construction
1. The roof truss supports could not
be welded to the wall, and
2. The wall had actually “moved”
across the property line into the
adjacent tenant’s property
Dave Jacob immediately queried
both men about the foundation design
that was selected to support the wall.
The GC explained that there was
intended to be an 18” to 36” wide spread
footing under the entire wall. Due to the
close proximity of the adjacent property
Fig. 2 North Wall of Store Showing
Lateral Bracing
When the three men finished
discussing the conditions at the north
-2-
wall, they quickly went to examine the
similar conditions at the structure’s
south wall. Although the settlement and
subsequent outward roll of the south
wall was not as severe as with the north
wall, the top of the south wall had rolled
outward (south) 1-7/8” inches near the
center of the wall’s 260 foot total length,
as recorded by the steel contractor. The
concrete slab also had a crack similar to
the crack at the base of the north wall.
The slab crack is shown in Figs. 3 and 4.
A similar foundation design change had
been made on this side of the building
due to the close proximity of the
property boundary.
The foundation
failure of the south wall was again
attributed to the eccentric loading on the
spread
footing
for
the
first
approximately 200 feet of the wall
measuring west to east. A photograph of
one of the cracks in the CMU block wall
is shown in Fig. 5.
Fig. 5 Example Vertical Crack in South
Wall of Store
Fig. 4 Close-up View of Example Floor
Slab Crack
Fig. 3 Example Floor Slab Crack
Adjacent to South Wall
-3-
After making the decision to
proceed, Dave Jacob called the GC and
provided him with a verbal price
estimate and a brief description of the
proposed solution. He also informed the
GC that Dwyer would commit to starting
the project on the following Monday,
October 21st. The proposed piering
method, the price and the start date were
all deemed to be tentatively acceptable,
and Jacob formalized the quotation,
terms and conditions in writing in
preparation for a meeting the next
morning - Wednesday.
Dave Jacob presented the
proposal as planned on Wednesday, and
the project was formally approved to
start on the following Monday.
Once the south wall examination
was complete, the three men returned to
the construction office to discuss a
potential remedy.
The ensuing
discussions focused on the amount each
wall would have to be rotated inward in
order to achieve a near plumb condition
and satisfy both the roof construction
requirements and the adjacent property
line restrictions.
Dave Jacob was
informed that each wall could not be
more than ¾ of an inch out of plumb in
order to complete the welding of the
steel roofing trusses, and this amount
would more than satisfy the property line
requirements. Additionally, Jacob was
informed the remediation project had to
be started immediately – preferably on
Monday, October 21 at the latest (only 6
days after the initial telephone call).
Dave was provided with a set of prints
for the project as well as the
geotechnical engineer’s soils report for
the site. He informed the two men that
he would be in touch later that day with
a proposal to return both walls to within
the required specifications.
Upon reviewing the job with
Dwyer engineers and piering specialists,
it was determined that piers would need
to be installed every five feet along the
walls. This meant that a total of 50 piers
would be required for the south wall and
60 piers for the north wall. It was also
decided that all piers for each wall
would have to have hydraulic rams
mounted on them simultaneously for
lifting, which would require Dwyer to
mobilize 60 hydraulic rams to the site to
complete the lift. It also necessitated
careful review and some rescheduling of
the piering projects already planned in
Dwyer branch offices located in
Cincinnati, Columbus, Lexington and
Louisville.
Building and Site Description
The mall project site is located in
West Chester, OH – a northern suburb of
Cincinnati.
The ground surface is
comparatively flat across the site.
Subsequently, minimal site grading was
performed in preparation of store’s
construction.
A view of the store from a
distance is shown in Fig. 6. A view of
the inside of the store at the time of
repair is shown in Fig. 7. This figure
reveals that the store consists of a
combination of masonry and steel
construction.
The rectangular store
footprint encompassed approximately
120,000 sq. feet, and measured roughly
310 ft x 400 ft.
Adjacent property lines to the
south and north walls were extremely
close. In fact, the store width was only 8
inches smaller than the lot width. This
condition
necessitated
that
the
foundation had to be virtually flush with
the block wall as shown in Fig. 8.
-4-
The north and south exterior
walls were to consist of 8” CMU block
with a brick veneer and foam insulation.
Both walls were grouted on 32” spacing.
The final height of the walls was 27 feet
from interior slab finished floor to the
top of the parapet. The foundation
extended approximately 30 inches below
the top of the slab.
The original
foundation design for these walls can be
summarized as follows:
Fig. 6 Distant View of Store Site
North Wall
The foundation for the north wall was
designed as follows:
0 to 250 feet – 26” wide, 12”
thick spread footing eccentrically offset
and vertically flush with exterior wall
250 to 310 feet – 18” wide, 12”
thick spread footing centrally located
under exterior wall
South Wall
Fig. 7 View from Inside Store
The foundation for the south wall was
designed as follows:
0 to 200 feet – 26” wide, 12”
thick spread footing eccentrically offset
and vertically flush with exterior wall
200 to 260 feet – 18” wide, 12”
thick spread footing centrally located
under exterior wall
Subsurface Conditions
The soil conditions on the site
predominantly consist of soft, wet silty
clays to lean clays with sand partings,
gravel, and rock fragments (glacial till)
that gradually stiffened with depth
Fig. 8 As-Built Spread Footing Shown
Nearly Flush with Exterior Wall
-5-
unsupported distance of eight feet.
Hence, the available load for pier
installation without risk of damage is the
weight of 16 feet of wall or about 40
kips. Pier installation to 35 kips could
be accomplished by installing the piers
individually thereby utilizing slightly
less than the available weight of the wall
at each pier location.
Lifting and rotation of the wall is
performed using all Magnum Piering
hydraulic rams simultaneously.
It
follows that the dead load on each pier
due to the partially constructed wall,
which was 12.5 kips per pier, should
correspond roughly to the lifting forces
that would be necessary. The true force
required for lifting may be higher than
this due to soil mobilization along the
interior of the foundation wall and
cohesion under the footing.
underlain by stiff layered shale and interbedded hard limestone at a depth of 7.5
to greater than 15.4 feet. Ground water
was typically encountered at depths of 1
to 3 feet below the ground surface at the
time of drilling.
Foundation Loads
The building was designed with
an internal steel frame and external
masonry walls. The structure’s roof
system consisted of steel bar joists with
corrugated metal deck and standard
built-up roof materials. The masonry
walls were load bearing and spaced
approximately 22 feet from the closest
set of interior steel columns. Thus, the
walls supported approximately 11 ft of
tributary roof loads and their own
weight.
The estimated dead load of the
walls and foundation prior to attachment
of the roof joists and installation of the
brick veneer is 2.5 kips/lf.
After
construction is completed, the total live
and dead load on the walls is on the
order of 4.5 kips/lf. This assumes a 20
psf snow load for the Ohio area.
The required total dead and live
design load capacity of the piers spaced
5 feet on-center is 23 kips. Applying a
factor of safety of 1.5, indicates that
each pier must be installed and load
tested to a minimum of 35 kips.
Since the weight of the structure
itself is used as resistance for the
installation of this type of hydraulically
driven steel push pier, pier spacing is
typically governed by the weight of the
structure that can be utilized safely
without risk of overstressing and
cracking the foundation and wall. It
could be assumed that the store wall
was, at a minimum, designed to span an
Alternative Repair Solutions
The store owner and the general
contractor considered tearing down and
replacing both walls and their respective
foundations, but the added construction
costs and lost time made this extremely
expensive option a last resort. Using the
Magnum Piering remedial steel push
pier
underpinning
system
was
considered to be the most economical
solution with the least amount of impact
on the overall construction schedule.
Other systems that may have
been considered are helix remedial piers
or concrete piers. Each of these systems
has drawbacks. Helix piers generally
introduce more disruptive loads to the
structure due to the larger eccentricity of
helix pier brackets. It is also more
difficult to use helix piers to achieve the
precise, uniform, and controlled lift that
was required by project tolerances.
-6-
rotational eccentricities. This step could
be skipped, since the footing was already
flush with the wall above. Bracket
installation is shown in Fig. 10.
Next, the ram assembly is
attached to the bracket and the
installation of 30 inch sections of 3 inch
O.D. high strength steel pier shaft is
conducted, as shown in Fig. 11.
Concrete underpinning piers are
generally cost prohibitive and could not
be installed within the property line
restrictions.
Concrete piers would
require much more time to install, and
they would not transfer loads below the
soft soils with the building loads
available due to increased installation
pressures of the larger diameter concrete
cylinders.
Considering
time,
cost,
practicality, and sound engineering,
hydraulically driven steel push piers
were found to be the best solution for
this project. Dwyer Concrete Lifting has
been using the Magnum Piering Steel
Push Piering System for over 10 years,
and the firm has successfully stabilized
thousands of commercial and residential
foundations in the region.
Installation Data
Fig. 9 Marking Bracket Positions Along
Foundation Walls
The process of pier installation
began by excavating along the exterior
of the foundation as shown in Fig. 8. A
site safety meeting was held whereby
crews were briefed on construction
hazards, and a wall monitoring program
was set in place.
Next, bracket positions were
marked along the wall, as shown in Fig.
9. Each Magnum Piering bracket was
secured using ½ inch diameter by 5½
inch long, expansion bolts extending into
the side of the footing. Normally, the
footing is chipped flush with the
foundation wall prior to bracket
installation in order to minimize
Fig. 10 Bracket Installation
-7-
At the store, the design ultimate
capacity of each pier was 35 kips. In
order to add to the factor of safety and
ensure proper pier installation, Dwyer
personnel installed each pier to the
maximum load that could safely be
applied to the structure (40 kips), which
corresponds to a hydraulic ram pressure
of approximately 5,000 psi. The final
depth of the piers along the North and
South walls of the building are shown in
Figs. 14 and 15.
As can be seen in the figures, the
final depth of the piers along the North
wall varied from 10 to 20 feet below the
top of slab and along the South wall
from 15 to 19 feet. In either case, a
discernable profile is evident.
The
reason for larger variation in pier depth
on the North side of the site is unknown.
However, the depth of the piers was
generally consistent with the depth and
variability of bedrock described in the
geotechnical engineer’s report for the
project site. It was concluded that all
piers are likely supported on or within
the bedrock.
Fig. 11 Pier Installation
Hydraulic pressure during pier
installation is recorded at various depths,
as shown in Fig. 12. A log of these
readings is prepared for each pier
location. Pier installation is halted once
the hydraulic pressure corresponding to
the design ultimate capacity of the pier is
reached. At that point, the load is
maintained on the pier and movement is
monitored over a period of time until the
pier movement decreases to less than
1/16th inch per ½ hour. This process
constitutes a full-scale load test at each
pier location.
Fig. 13 Monitoring Wall Movement
During Lifting Phase
Fig. 12 Logging Pier Depth and
Hydraulic Pressure
-8-
Survey stations were established
inside and outside the building in order
to monitor movement, as shown in Fig.
13.
After all piers were individually
installed, it was time to lift and rotate the
building walls back to within tolerances
for plumbness. All rams were utilized
simultaneously in the lifting process.
Pier # - West to East
Depth of Piers from Top of Floor Slab (Feet)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
2
4
6
8
10
12
14
16
18
20
22
Fig. 14 Final Pier Depths Along North Wall
Pier # - West to East
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
Depth of Piers from Top of Floor Slab
(Feet)
0
2
4
6
8
10
12
14
16
18
20
Fig. 15 Final Pier Depths Along South Wall
-9-
61
4
Deflection (Inches)
3
2
1
0
-1
Before Lift
After Lift
-2
-3
c1
b
c
d
e
f
g
h
j.2
Deflection Benchmarks - 10 Points
Fig. 16 Initial and Final North Wall Top Location
4
Deflection (Inches)
3
2
1
0
-1
Before Lift
After Lift
-2
-3
c1
b
c
d
e
f
g
h
Deflection Benchmarks - 10 Points
Fig. 17 Initial and Final South Wall Top Location
-10-
j.2
the inside of the wall and cohesion
below the footing.
After lifting, each bracket was
rigidly fixed to the piers using two ¾
inch diameter grade 8 bolts.
The
hydraulic ram assemblies were removed,
and the tops of the piers were cut flush
with the tops of the brackets.
Backfilling of the trench commenced
and the piers were concealed.
Both walls were successfully
relocated. Initial and final top of wall
locations with respect to plumb are
shown in Figs. 16 and 17. The North
and South walls were restored to within
½ inch of plumb, except for the Eastern
portion of the South wall. The reason
for this discrepancy is that the wall was
not constructed perfectly straight. It was
identified during this phase that the
South wall had started to settle during
masonry construction, and the block
mason had to adjust the course of the
wall. Afterward, the wall continued to
move and eventually ended in the
position where Dwyer was called to the
site. The wall could not be improved
beyond that shown unless it was
reconstructed. It was deemed that the
lift was acceptable and the underpinning
project was completed.
Lifting was achieved at ram
pressures of approximately 2,000 psi,
which corresponds to a load of 16 kips.
As expected, lifting forces were slightly
higher than the dead load of the wall,
12.5 kips, due to soil mobilization along
Conclusions
The store walls were successfully
repaired using hydraulically driven steel
push piers.
The piers caused no
discernable damage to the structure
during installation.
Each pier was
installed and load tested to a factor of
safety of 1.7 times the design total live
and dead load of the completed
structure.
The entire 110 pier
underpinning project was completed
within 8 working days from the start
date and at a cost significantly less than
the cost to reconstruct both walls.
-11-
Axial Capacity of Hydraulically-Jacked, Steel-Pipe Micropiles Used for Underpinning
June 14, 2002
Abstract
A review of the axial capacity of hydraulically-jacked, steel-pipe micropiles used for
underpinning is presented. A procedure is suggested for field verification of underpinning pile
capacity. Theoretical calculations of pile capacity are compared with measured values for a
case study involving a foundation repair performed on a telecommunications building.
Introduction
Push pier, push pile, and resistance
pier are some of the trade names often applied
to hydraulically-jacked, steel-pipe micropiles
used for underpinning. For convenience the
term steel push pier will be used herein.
There are several different manufacturers of
steel push piers including Magnum Piering,
RamJack, and Atlas Systems. Although steel
push piers can be installed using heavy
machinery for construction of new structures,
this paper is focused on piers used exclusively
for underpinning and repair of existing
structures.
Steel push piers essentially consist of
short sections of pipe or structural steel tube
that are often coupled together by an internal
sleeve. Each section of a steel push pier is
forced into the ground using a hydraulic ram
fastened to the footing, stem wall, or grade
beam of an existing structure. In this way, the
weight of the structure provides the resistance
necessary to force the pier into the ground. A
factor of safety is obtained by installing the
piers individually and by using more piers
than the number required to carry the weight
of the structure. An example steel push pier
connected to a footing foundation is shown in
Fig. 1. A photograph that depicts steel push
pier installation is shown in Fig. 2.
Fig. 1 Example Steel Push Pier
-1-
1.
2.
3.
4.
5.
Integrity of the structure at pier location
Connection between bracket and structure
Mechanical strength of the bracket
Buckling strength of the pier
Soil friction and bearing pressure
Although each of these factors is equally
important, the topic of this paper is the
capacity provided by soil friction and bearing
pressure. It is assumed for the remainder of
this discussion that the first four factors are
adequate to support the required load on the
pier.
Fig. 2 Example Push Pier Installation
Capacity Requirements
The required capacity of a steel push
pier used for underpinning is computed by the
same techniques as those used for other deep
foundations with a few special precautions.
As with other foundation types, a push pier
must have sufficient capacity to support the
dead and live loads of the structure. If a
structure is to be lifted and re-leveled, it is
essential to add the weight of the soil above
the footing to the total dead loads computed
by conventional means. The cohesion of the
soil on the bottom of the footing and/or slab
and the friction of the soil along the
foundation wall or grade beam also need to be
considered.
Demonstrating the ability to lift and relevel the structure is an insufficient
verification of push pier capacity. Foundation
underpinning must also be capable of
supporting live loads such as snow, wind,
people, and furnishings that may be added to
the structure at a later time. It is imperative
that live loads are taken into account in the
layout and spacing of push piers.
Total dead and live loads represent the
required design capacity of push pier
underpinning.
In general practice, an
appropriate factor of safety must then be
Steel push piers are used to underpin
an existing spread footing or slab-on-grade
foundation that has undergone excessive total
or differential settlement. Once all of the
piers are in place, the structure can be lifted to
its original grade. This often results in crack
closure and provides relief to over-stressed
structural members.
The rate of installation of a single steel
push pier varies among installers and depends
on the subsurface conditions. The typical time
required to install a 20 ft long push pier is
generally in the range of 4 to 8 hrs. A shear
ring with a diameter slightly larger than the
pier shaft is usually placed at the bottom of the
pier. The purpose of this ring is to reduce
friction along the shaft during installation,
which permits greater depths to be achieved.
Although some of the capacity of a push pier
is due to friction of the soil along the sides of
the pier, the use of a shear ring effectively
produces an end bearing pile.
Steel push piers are fastened to an
existing structure by the application of a
foundation bracket. The capacity of a steel
push pier depends on five factors, given as
follows:
-2-
applied to derive the required ultimate
capacity. Factors of safety used in foundation
engineering vary depending on the reliability
of soil and subsurface information, the
heritage of particular foundation capacity
determination methods, and the sensitivity of
the structure to movement. A factor of safety
of 3 is generally used in conjunction with
spread footing foundations. The American
Society of Civil Engineers Publication 20 96,
“Standard Guidelines for Design and
Installation of Pile Foundations”, explains that
a factor of safety of 1.5 is permissible for
driven pile foundations since the method of
installation provides a means of capacity
determination in the field. Installation of a
steel push pier provides an even more direct
means of capacity determination as compared
to pile driving. The engineer of record should
select a factor of safety suitable for each
project and site conditions. A factor of safety
between 1.5 and 2.0 is often used in practice
for steel push pier installation.
7.
8.
9.
10.
11.
12.
location is measured and a building
monitoring program is established
Hydraulic rams are temporarily
attached to the brackets on the existing
structure
Steel push piers are jacked into the
ground individually until the load used
for driving the pier equals or exceeds
the required ultimate capacity
Ram pressure is measured and
recorded at 3 feet intervals of push
pier depth
Local building official or building
owner’s representative observes pier
loading and verifies required capacity
has been achieved
After all piers are installed and
inspected, the building is lifted and releveled to the extent possible without
compromising integrity of the
structure
The piers are permanently secured to
the brackets and the hydraulic rams
are removed
Final building elevation is recorded
Access holes are backfilled and
landscaping materials are restored
Field Verification of Capacity
The installation of steel push piers
generally involves the following procedures:
13.
14.
1.
To date, no standard method exists for
completion of installation steps 7 and 8 which
involve field verification of push pier
capacity. The American Society for Testing
and Materials specification D1143 - 81,
“Standard Test Method for Piles Under Static
Axial Compressive Load” explains routine
methods to determine if a pile has adequate
bearing capacity. Based in large part on this
standard, the following procedure for
verifying the capacity of a steel push pier is
suggested.
2.
3.
4.
5.
6.
An engineer or contractor’s technical
representative observes the condition
of the structure, computes building
loads, and plans push pier locations
All underground structures and
utilities in the vicinity of the piers are
located and moved or avoided
Foundation access holes are excavated
at each pier location
Existing foundation is modified to
allow connection of brackets as close
to foundation wall face as possible
Piering brackets are mounted to the
existing foundation
Elevation of the structure at each pier
1.
-3-
The bracket and ram assembly shall be
such that loads are applied vertically
2.
3.
4.
5.
6.
7.
8.
9.
and directly to the central longitudinal
axis of the push pier with a minimum
of eccentric loading
The structure to which the bracket and
ram assembly is attached shall have
sufficient integrity and weight to allow
for application of loads to the push
pier without excessive lifting and
without causing damage to the
structure
If the structure is of insufficient
weight to permit the required push pier
loading, then an earth anchor, ballast
weight, or battered pile must be used
to provide the necessary reaction
The hydraulic ram used to load the
pier shall be fitted with a pressure
gauge, shall be capable of delivering
the prescribed loads with a sensitivity
of at least 2% of the required ultimate
capacity of the pier, and shall be
calibrated at least annually
Push piers shall have a minimum
spacing of 2 feet or at least 10% of
their average depth
After the pier is installed and is ready
to be proof loaded, the loading
procedure shall consist of applying the
design ultimate load to the pier, which
shall be at least 150% of the design
allowable load
Push pier movement relative to a fixed
frame of reference shall be measured
optically or through the use of a dial
gauge
The proof load shall be maintained
until the rate of settlement is not
greater than 1/16 in/h but not less than
1h
A field report shall be prepared that at
least shall contain pier location,
applied loads, load duration, and final
pier depth
Theoretical Capacity
In practice, the theoretical capacity of
a steel push pier is seldom computed due to
the measurement and verification of capacity
in the field. However, on certain occasions it
may be desirable to determine theoretical
capacity in order to evaluate the suitability of
a particular bearing stratum or to approximate
push pier depth.
A case history is presented for a twostory, 12,000 sf, telecommunications office
structure in Cincinnati, OH. The south sides
of the building had experienced excessive
settlement. A plan view of the structure is
shown in Fig. 3. Exploratory borings were
drilled at the three locations shown. Graphic
logs of these borings are provided in Fig. 4.
As can be seen from the boring logs, the
subsurface conditions consisted of 0 to 3 feet
of fill over sandy clays and highly weathered
shale underlain by hard shale and limestone
bedrock at depths between 14 and 19 feet.
In most cases, underpinning the entire
structure with steel push piers is the
recommended course of action. In this
particular case study, the north ends of the
building were underlain directly by the hard
shale and limestone bedrock. It was decided
that the north sides of the building were
adequately supported and did not require
underpinning. A total of 24 steel push piers
were located and installed along the south
sides of the building, as shown in Fig. 3. The
depth of pier installations varied from 3 to 21
feet.
All of the piers were installed
individually and proof loaded to at least 45
kips. Hydraulic ram pressure was measured
and recorded at installation depth intervals of
3 ft. Ram pressure and corresponding load is
shown in Table 1 for the three piers located
closest to the exploratory soil borings.
-4-
Table 1. Records of Push Pier Installation
Pier Location
3
14
20
Hydraulic Ram Pressure (psi) - Applied Load (lbs)
Depth
3
500
4,125
200
1,650
100
6
500
4,125
500
4,125
100
825
9
1,000
8,250
1,500 12,375
1,000
8,250
12
5,500 45,375
5,500 45,375
3,000 24,750
15
5,500 45,375
18
Fig. 3 Case History Site Plan
LOGS OF EXPLORATORY BORINGS
B-1
B-2
B-3
0
0
32/12
38/12
11/12
31/12
15/12
5
13/12
23/12
26/12
31/12
13/12
30/12
19/12
17/12
80/3
59/12
72/12
139/12
100/5
Depth (ft)
60/6
77/6
Legend:
Asphalt Concrete
Weathered Shale
Gravel Basecourse
Shale and Limestone
Fill, Clay, Sandy
25
15
67/12
Clay Glacial Till
80/3 Standard Penetration
Resistance Test Blow
Count (blows/inches)
Fig. 4 Logs of Exploratory Borings
-5-
20
25
Depth (ft)
10
15
20
5
11/12
10
97/12
825
Due to the use of a shear ring, a steel
push pier should be treated essentially as an
end bearing pile. According to Meyerhof
(1956, 1976), ultimate static pile point
capacity can be related directly to Standard
Penetration Resistance test blow count by
P p tu = 8 40 A N
the penetration length, L, is not associated
with friction along the pile shaft; rather, it is
an indication of the effective vertical pressures
that govern the Nq term in the traditional
bearing capacity equation. As such, it is
reasonable to use a fraction of the push pile
depth.
In applying Meyerhof’s equation to the
data available for the case history, it was
assumed that the penetration length, L, is
equal to 25% of the depth of the pier minus
1.5 ft to account for disturbed soil at the
ground surface. In terms of mathematical
symbols, L is given by
L
D
where A = pile tip area (ft2);
N = SPT blow count (blows/ft);
L = penetration length (ft),
and D = pile diameter (ft).
L = 2 5 % × ( L T − 1.5 )
Meyerhof also specified the criterion that
where LT = total depth of the pier (ft).
A comparison between theoretical and
measured pier capacity for the three piers
given in Table 1 is shown in Fig. 5. These
data are for all depth intervals. As can be seen
in the figure, Meyerhof’s equation and the
definition of penetration length given above
match the field measurements very well.
L
≤ 10
D
It has been shown (Miller and
Lutenegger, 1997) that open-ended piles
exhibiting a plugged condition develop end
bearing similar to that of a closed-ended pile.
It has also been calculated that plugged
conditions are achieved at depths between 10
and 20 pile diameters (Paikowsky and
Whitman, 1990). This is consistent with the
authors observation that push piers typically
develop a plugged condition within the
completion of the first 3' section of pier pipe
installed. Hence, in almost all practical cases,
the pile tip area, A, should include the area of
the plugged end. Pile tip area should also
include the additional diameter provided by
the shear ring (if used).
The steel push pier diameter, D, used
for the case history presented above was 3".
The shear ring diameter was 4". The standard
penetration resistance blow count used in the
above equation should be taken as the average
value from 3 D below the pile tip to about 8 D
above the pile tip. Since Meyerhof’s equation
is for tip capacity, it should be recognized that
Discussion
In saturated low permeable soils, the
installation of steel push piers causes high
pore water pressures. Subsequently, soil
effective stress is reduced substantially. It is
standard practice to proof load steel push piers
immediately after installation. This procedure
is conservative since the capacity of the pier
should increase substantially after pore
pressures dissipate and effective stresses
return to steady state.
It is common
knowledge amongst installers that push piers
must be completely installed in the same day.
Even an overnight delay is sufficient to make
the obtainment of additional installation depth
difficult. In most cases, push pier capacity
should increase with time. Groundwater
fluctuations and corrosion are exceptions that
may adversely affect capacity.
-6-
60000
Theoretical Capacity (lbs)
50000
40000
30000
20000
10000
0
0
5000
10000 15000 20000 25000 30000 35000 40000 45000 50000
Push Pier Field Capacity (lbs)
Fig. 5 Theoretical and Measure Push Pier Capacity
References
American Society for Testing and Materials
(1994) “Standard Test Method for Piles Under
Static Axial Compressive Load” Test
Designation D1143
Meyerhof, G.G. (1956) “Penetration Tests and
Bearing Capacity of Cohesionless Soils”, J. of
Soil Mechanics and Foundation Design,
ASCE, Vol. 82, SM 1, pp. 1-19
American Society of Civil Engineers (1996)
“Standard Guidelines for Design and
Installation of Pile Foundations” Publication
20-96
Miller, G.A. and Lutenegger, A.J. (1997)
“Influence of Pile Plugging on Skin Friction in
Overconsolidated Clay”, J. of Geotechnical
and Geoenvironmental Eng., ASCE, Vol. 123,
No. 6, p. 525
Meyerhof, G.G. (1976) “Bearing Capacity and
Settlement of Pile Foundations”, J. of
Geotechnical Eng., ASCE, Vol. 102, GT 3,
pp. 195-228
Paikowsky, S.G. and Whitman, R.V. (1990)
“The Effects of Plugging on Pile Performance
and Design” Can. Geotech. J., Ottawa,
Canada, No. 27, pp. 429-440
-7-
Lateral Loads and Bending Moments Associated with Steel Pier Foundation Brackets
Used for Underpinning Existing Structures
July 7, 2002
Abstract
The fundamental mechanics of a bracket and foundation connection are demonstrated. A
static analysis was performed on an example steel pier foundation bracket used for underpinning
an existing foundation. Strain compatibility between the connection to the structure and the bending
resistance of the pier was investigated using a computer program for the analysis of pile foundations
under eccentric loads. The lateral load and overturning moment exerted on an existing foundation
due to eccentricity of steel pier foundation brackets were quantified for various soil types. The
results of these analyses were used to examine the viability of steel pier underpinning given the
strength of an existing foundation.
Introduction
There exist a number of possible
methods for repair of a footing or mat
foundation that has undergone excessive total
or differential movement. One common
method of repair is the use of hydraulicallyjacked steel pipe micropiles (steel push piers)
for underpinning. This method consists of
installing a steel pier adjacent to an existing
foundation and then attaching the pier to the
foundation by application of a bracket.
Steel pier foundation brackets must be
placed as close to the center of the existing
foundation as possible. Often, the process of
attaching a bracket involves chipping away a
section of the footing so the bracket can be
aligned with the outside face of the foundation
wall. A typical steel pier underpinning
foundation bracket is shown in Fig. 1. Despite
considerable care in placing the bracket, some
eccentricity is inevitably introduced, since the
pier cannot be placed directly under the
centerline of the foundation wall for practical
reasons.
Fig. 1 Example Steel Pier Foundation
Bracket
One of the common concerns
regarding the application of steel pier
underpinning is the susceptibility of the
existing foundation to damage caused by
forces and moments in the connection
between the bracket and existing concrete
foundation elements. In order to evaluate the
viability of using steel pier underpinning, it is
necessary to compute the applied lateral loads
and overturning moments resulting from
-1-
eccentricity of the bracket and pier assembly.
With this information, it is possible to
compute the factor of safety between applied
loads and the available strength of the
foundation.
A static analysis was conducted to
evaluate the stability of an example
foundation bracket for steel pier underpinning.
Strain compatibility between the connection to
structure and the bending resistance of the pier
were investigated using a computer program,
LPILE Plus for Windows by Ensoft, Inc. The
lateral load and overturning moment exerted
on an existing foundation due to eccentricity
of an example steel pier foundation bracket
were quantified for various soil types. The
results of these analyses were applied to
examine the
viability of steel pier
underpinning.
Static Analysis
There are several manufacturers of
steel pier underpinning foundation brackets.
In general, foundation brackets can be
categorized as either plate brackets or angle
brackets. A cross-sectional view of an
example plate bracket is shown in Fig. 2. This
assembly is manufactured by Magnum
Piering, Inc. of Cincinnati, OH and is
protected under U.S. Patent No. 5,234,287
(Magnum Piering, Inc., 2002). Atlas Systems,
Inc. also manufactures a plate bracket,
however it differs from the Magnum bracket
in the way that the pier is connected to the
bracket (Atlas Systems, Inc. 2000). An
example of an angle bracket is shown in
Fig. 3. This example is not modeled after any
particular manufacturer, however it is similar
to several that are currently available.
Two characteristics that are shared by
all brackets are a face plate that mounts
vertically on the existing foundation (A) and
a sleeve or pair of clamps that prevent the pier
Fig. 2 Plate Bracket Free Body Diagram
Fig. 3 Angle Bracket Free Body Diagram
-2-
from moving laterally (B). Angle brackets
also have an angle plate that extends below
the foundation (C).
Provided the sleeve or clamps (B) are
sufficient to prevent rotation of the pier with
respect to the bracket, the total vertical load
supported by the pier can be represented as a
single resultant force, P2, located at the central
axis of the pier shaft. If the existing
foundation upon which the bracket is mounted
is sufficiently rigid, then the total force
applied by the existing foundation can be
represented as a single resultant force, P1,
located close to the face plate (A).
The exact location of the applied force,
P1, on the bracket depends on the connection
of the bracket to the structure. For plate
brackets, such as the one shown in Fig. 2, the
applied force, P1, is transferred by concrete
anchors and acts immediately adjacent to the
face plate (A).
For most angle brackets, such as the
one shown in Fig. 3, the majority of the
applied force, P1, is transferred through the
bottom of the foundation concrete to the angle
plate (C). The distance from the face plate of
an angle bracket to the resultant applied force,
P1, depends on the roughness of the existing
concrete, occurrence of exposed aggregate,
and mechanical rigidity of the bracket itself.
The total overturning moment, M0,
resulting from eccentricity of steel piering
brackets is given by
M0=
Resistance to overturning is provided
by the moment resistance of the connection
between the bracket and the structure, M1, and
the moment resistance of the pier in the soil,
M2. The magnitude of each of these moment
reactions depends on the strain compatibility
between them. If the connection to the
structure is very rigid compared to the strain
necessary to mobilize the moment resistance
of the pier in the soil, then M1 will be much
greater than M2. A strain compatibility
analysis was performed and the results are
given in the next section.
The lateral force, L1, is the horizontal
component of force exerted by the connection
between the existing structure and the bracket.
It is a combination of horizontal loads in the
anchor bolts, compression behind the face
plate (A), and friction along the angle plate
(C). In order for the condition of static
equilibrium in the x-direction, perpendicular
to the face of the bracket (A), this force must
be equal and opposite to the horizontal
component of force at the top of the pier, L2.
The horizontal component of force at the top
of the pier may be due to a departure of the
pier from plumbness. Lateral force in the
connection between the existing structure and
the bracket may be due to horizontal loads on
the structure such as wind or active earth
pressures. These causes of lateral force are
ubiquitous to all foundations, can be
addressed using conventional techniques, and
will not be discussed further herein.
Another cause of lateral loads is
inherent to the application of eccentric loads
and their resulting moments to the tops of
steel piers. If a moment is applied to the free
end of a steel pier embedded in the ground,
the pier will move laterally as the soil
becomes mobilizes to resist the applied
moment. If the pier head is prevented from
moving laterally, then a horizontal component
( P 1 + P 2)
e
2
where e = total eccentricity. In order for
static equilibrium in the z-direction, parallel
with the face of the bracket (A), the total
vertical load supported by the pier, P2, must be
equal to the total force applied to the existing
foundation, P1, and hence
M 0 = P1 e
-3-
of force must be applied to maintain the
position of the pier head. The magnitude of
this reaction was determined for steel piers in
different soils. A description of the analysis
and the results are given in a later section.
AC01-0402-R1), the allowable displacement
of ½" diameter anchor bolts under design
tensile loads is 0.0500 inches. If the anchor
bolts are have a design tensile capacity of 3.5
kips, which is typical for anchors spaced 3"
O.C. and embedded 4" in 4,000 psi concrete
(Illinois Toolworks, Inc., 2001), then the
moment generated in the connection is on the
order of 150 kip-in and the rotation of the
bracket, 1, is approximately 0.4 deg (arcsin
0.0500"/7").
Stain Compatibility
It is well known in the field of
mechanics of materials that stress and strain
are intimately related. Loads and moments
must be accompanied by displacements and
rotations. In order to generate a resisting
moment, M1, in the connection between the
existing foundation and the bracket, a small
amount of rotation must occur. Likewise, in
order to generate a resisting moment in the
pier, M2, some rotation of the pier in the soil
must occur. The angles of rotation are shown
in Fig. 4. Assuming that the connection
between the bracket and pier is very rigid and
the structure itself is very rigid, the rotation of
the pier in the soil and the rotation of the
bracket connection with respect to the
structure must be equal.
θ1 = θ 2
The first step in determining rotational
compatibility is to establish the relationship
between bracket rotation and applied moment.
The amount of rotation in the connection
between the existing structure and the bracket,
1, as a function of applied moment, M1, is
different for the many types of foundation
brackets available. An example calculation is
provided here using a Magnum Piering
bracket with 6 anchor bolts located 7" from
the top of the bracket (Magnum Piering, Inc.,
2002).
The rotation of a bracket that
incorporates the use of concrete anchors can
be roughly estimated by examination of the
displacement of the anchor bolts under tensile
loads. According to the acceptance criteria for
expansion anchors in concrete (ICBO Report
Fig. 4 Rotation Compatibility
The second step in determining
rotational compatibility is to determine the
relationship between rotation of the top of the
pier, 2, and the moment generated in the soil,
M2. This relationship is a function of the
rigidity of the pier and the stiffness of the soil.
An example set of relationships was generated
using 3" O.D., 1/4" thick wall and 1/8" thick
wall Magnum Push Piers (Magnum Piering,
Inc., 2002).
-4-
200
180
Bracket Connection
to Structure
Resisting Moment (kip-in)
160
140
120
1/4 Wall Pier
100
80
1/8 Wall Pier
Soft
Clay
60
Soft
Clay
Stiff
Clay
Stiff
Clay
40
20
0
0
0.1
0.2
0.3
0.4
0.5
0.6
Rotation Angle (deg)
Fig. 5 Rotational Compatibility
The rotation of the example pier was
determined using LPILE Plus for Windows
software. Typical properties for various soils
were assumed (Reese, L.C., et al., 2000). The
top of the pier was fixed with respect to lateral
displacement. A small range of rotation
angles was input as boundary conditions and
the resulting moments at the top of the pier
were computed. Results are shown in Fig. 5.
rotational compatibility, the rotation angle of
the pier and the bracket connection must be
equal (1=2).
For the example case
presented here, the bracket connection to the
structure has approximately 3 to 7 times as
much moment resistance as the pier in
different soils.
In order for static equilibrium, the
summation of the reaction moment in the
connection of the pier to the structure and the
reaction moment of the pier in the soil must be
equal to the applied moment due to
eccentricity of the vertical loads, as given by
As can be seen in Fig. 5, the rotation
required to generate resisting moments of the
pier in the soil are much greater than the
rotation necessary to generate the same
moment for the bracket connection to the
structure. According to the condition of
M1+ M 2 = M 0
If a single new parameter, , is defined to
account for rotational compatibility, where -5-
loads were determined for 3" O.D., 1/4" and
1/8" thick tubular shafts which are indicative
of Magnum Push Piers (Magnum Piering, Inc.,
2002) and other manufactured steel piers.
Results are provided in Figs. 6 though 9.
The results of the lateral force analysis
indicate that pier stiffness differences between
the 0.125" thick and 0.250" thick wall pipe
piers produce negligible differences in the
magnitude of lateral force as a function of the
applied moment to the top of the pier. The
results also indicate that larger lateral forces
are produced in more dense or more stiff soils.
The graphs shown in Figs. 6 through 9 can be
used to estimate the lateral force exerted on an
existing foundation due to steel pier
underpinning if the brackets and piers are the
same as or similar to those manufactured by
Magnum Piering, Inc. In the next section, the
results of the static, strain compatibility, and
lateral load analyses are used to predict the
lateral and overturning moments exerted on an
existing foundation due to steel pier
underpinning.
is the ratio of M2 to M1, then the equation for
moment equilibrium can be rewritten, as given
by
M 1 (1 + λ) = M 0 = P 1 e
The rotational compatibility factor, ,
is a function of soil conditions, pier shaft
rigidity, and bracket connection to the existing
structure. For the Magnum Push Pier used in
the example herein, the rotational
compatibility factor has the following values.
Table 1. Rotational Compatibility Factor for
Magnum Push Piers and Brackets
factor
Shaft Thickness
Soil Type
.23
0.250
soft clay
.35
0.250
stiff clay
.22
0.250
loose sand
.27
0.250
med. sand
.15
0.125
soft clay
.22
0.125
stiff clay
.14
0.125
loose sand
.17
0.125
med. sand
Bracket Reactions
An example calculation of the lateral
forces and overturning moments caused by
steel pier underpinning is presented using the
Magnum Piering brackets and push pier
products used in prior sections of this report.
Similar calculations can be performed using
the steel piering products of other
manufacturers if the specifications of those
products are known. The goal of this exercise
is to provide a working example that
demonstrates the fundamental mechanics of a
steel pier and bracket connection to an
existing structure. Although the specifications
for Magnum Piering products are used in the
example, it is recognized that other
manufacturers systems may be analyzed in a
similar manner.
Lateral Forces
As stated previously, the generation of
moments in the pier without lateral movement
can only be accomplished if the existing
structure is capable of providing a lateral
restraining force. The magnitude of lateral
load required to restrain the pier head can be
determined by again incorporating LPILE Plus
for Windows software. Required lateral
restraint is a function of the pier shaft rigidity
and the stiffness of the soil. Example lateral
-6-
3" O.D., 0.125 Thick Wall Pipe Pier
Fig. 6 Lateral Loads for Fixed-Head Steel Piers in Loose Sand
Fig. 7 Lateral Loads for Fixed-Head Steel Piers in Medium Dense Sand
Fig. 8 Lateral Loads for Fixed-Head Steel Piers in Soft Clay
-7-
Fig. 9 Lateral Loads for Fixed-Head Steel Piers in Stiff Clay
For the example calculation, it will be
assumed that 3" O.D., 0.250" thick wall push
piers are used to underpin an existing
foundation, the piers penetrate a stiff layer of
clay soils, and that the design load on each
pier is 30 kips. Magnum Piering plate and
angle brackets have an eccentricity, e, between
the center axis of the pier and the face of the
bracket of about 2". Hence, the applied
moment, M0, is given by
According to the right-hand chart in
Fig. 9, the lateral load on the existing
foundation caused by a bending moment of 16
kip-in for a 3" O.D., 0.250 thick steel pipe pier
in stiff clays is approximately -1 kip. The
negative sign indicates that the bracket is
being pulled away from the foundation due to
the bending of the pier under the applied
eccentric loads.
M 0 = ( 3 0 kip s ) (2 in ch es ) = 6 0 kip in
Discussion
In summary, the example underpinning
application examined in the previous section
would exert on the existing foundation an
overturning moment equal to 44 kip-in and a
lateral load of -1 kip where the negative sign
indicates tension. These loads are in addition
to the more obvious design vertical load of
30 kips. In order for steel pier underpinning
to be a viable alternative for repair of an
existing foundation under these example
conditions, the existing concrete foundation
elements must be capable of withstanding
these loads.
In the preparation of this work, push
piers were assumed to be rigidly fixed to their
brackets so that rotation between the bracket
According to Table 1, the rotational
compatibility factor, , for a 3" O.D., 0.250
thick steel pipe pier in stiff clays with a
Magnum Piering or similar bracket is 0.35.
Hence, the overturning moment exerted on the
existing foundation due to the underpinning is
given by
M1=
1
( 6 0 kip in ) = 4 4 kip in
1 + 0 .3 5
and the moment resisted by the pier in the soil
is simply given by
M 2 = 6 0 kip in − 4 4 kip in = 1 6 kip in
-8-
and pier is negligible. During steel push pier
installation, the pier is typically not integrally
attached to the bracket. However, the ram
assembly used to install the pier often is
attached in a manner that limits pier rotation
relative to the bracket. It is possible and
perhaps probable that some small amount of
rotation of the pier with respect to the bracket
may occur during installation and prior to
bolting the pier to the bracket. This rotation
would increase the reaction moment carried by
the pier in the soil and, consequently would
result in a larger rotational compatibility
factor, . Hence, the foregoing analysis is
conservative with regard to moments in that it
tends to overestimate the moment transferred
to the existing foundation, whereas, it is
unconservative with regard to lateral loads,
because it tends to underestimate the lateral
loads exerted on the existing foundation.
A literature search was performed in
the preparation of this study. Specific
references regarding the analysis and
determination of lateral loads and bending
moments associated with underpinning
brackets were not found. Yet, steel pier
underpinning has been used to repair
structures in the United States for at least 50
years. There are more than 6 manufacturers of
steel pier underpinning systems and hundreds
of installation contractors. Due to their
widespread use, academic study of steel pier
underpinning and bracket connections to
structures is an important area of research that
should be encouraged.
Magnum Piering, Inc. (2002) “Magnum Push
Pier Technical Reference Manual” Corporate
Literature, Cincinnati, OH
Atlas Systems, Inc. (2002) “Piering Products
Manual”, Corporate Literature
Reese, L.C., et al. (2000) “Computer Program
LPILE Plus Version 4.0 User’s Guide” Ensoft,
Inc., Austin, TX 78718
Illinois Toolworks, Inc. (2001) “ITW
Ramset/Redhead Product & Resource Book”
Form No. FLC-6/01, Wood Dale, IL
References
ICBO Evaluation Service, Inc. (2002)
“Acceptance Criteria for Expansion Anchors
in Concrete and Masonry Elements” ICBO
Report #AC01-0402-R1
-9-
August 26, 2002
ATTENTION:
Mr. Bill Bonekemper
SUBJECT:
Concrete Wedge Anchor Capacity
For Magnum Piering Bracket
Per your request, concrete anchor bolt shear capacities were analyzed assuming eight
different bolt groups for use with Magnum Piering Plate Brackets. The analysis
generally followed recommendations provided by the anchor bolt manufacturing
company and those contained in the 1997 Uniform Building Code. The following are
assumptions used in that analysis:
1. Bottom of lifting bracket and concrete member are at the same elevation.
2. The concrete member is assumed to extend well beyond the sides and top of the
lifting bracket.
3. Reductions to applied load are based on recommended spacing and edge
distance requirements for shear and tension loads as taken from the ITW
Ramset/Red Head Product Resource Book, 2001.
4. Allowable loads for combined shear and tension forces are determined by the
following equation:
(Ps/Pt)5/3 + (Vs/Vt)5/3 1
Where:
Ps =Applied tension load
Vs = Applied shear load
Pt =Allowable tension load
Vt = Allowable shear load
4. Red Head Concrete Anchoring Systems ½” diameter Trubolt Wedge Anchors
with 4-1/8” embedment were assumed in analysis.
5. Trubolt Wedge Anchors ultimate tension and shear values for 2000, 4000 and
6000 psi concrete were taken from Ramset/ Red Head Product Resource Book,
2001.
6. Applied load “P” on the lifting bracket was assumed to be distributed 1.33
inches from the edge of the bolted plate in accordance with the paper on
eccentric loads on piering brackets by Howard A. Perko (2002). Normal weight
concrete was assumed for this analysis.
7. Normal weight concrete was assumed for this analysis.
It is important to note that the attached calculations are based on ultimate capacity of
the concrete wedge anchor bolt pattern. The bolt manufacturer and the Uniform
Building Code recommend using a factor of safety of 4.0 in order to determine design
capacity. This large factor of safety is typically assigned to wedge anchors, because
their capacity depends significantly on the method and care used in anchor bolt
installation and the quality of the concrete. We understand that the bolted connection
between a Magnum plate bracket and an existing foundation is tested to 150% of the
design capacity during push pier installation. The purpose of this test is to verify the
strength of the pier, bracket, and connection to the structure. Provided this type of field
capacity verification is used for every installation, then, in our opinion, a lower factor
of safety may be acceptable. In no case should a factor of safety of less than 1.5 be
used in the design with field verification or less than 4.0 without field verification.
Thank you for the opportunity to work with you on this project. If you have any
questions regarding this analysis, please do not hesitate to contact the undersigned.
Sincerely,
SECURE FOUNDATIONS & STRUCTURES, INC.
William R. Rebillet
Structural Engineer
ICBO Evaluation Service, Inc.
5360 WORKMAN MILL ROAD • WHITTIER, CALIFORNIA 90601-2299
A subsidiary corporation of the
International Conference of Building Officials
EVALUATION
REPORT
Copyright  2000 ICBO Evaluation Service, Inc.
ER-1372
Reissued March 1, 2000
Filing Category: FASTENERS—Concrete and Masonry Anchors (066)
ITW RAMSET/RED HEAD SELF-DRILLING, TRUBOLT
WEDGE, AND MULTI-SET II CONCRETE ANCHORS
ITW RAMSET/RED HEAD
1300 NORTH MICHAEL DRIVE
WOOD DALE, ILLINOIS 60191
1.0 SUBJECT
ITW Ramset/Red Head Self-Drilling, Trubolt Wedge, and
Multi-Set II Concrete Anchors.
2.0 DESCRIPTION
2.1 ITW Ramset/Red Head Self-Drilling Anchor:
2.1.1 General: The ITW Ramset/Red Head anchor is a selfdrilling concrete expansion shell anchor with a single cone expander. Both elements are made from heat-treated steel. The
steel for the body conforms to AISI C-12Ll 4, and the steel for
the plug conforms to AISI C-1010. The anchor has eight sharp
teeth at one end and is threaded internally at the other end.
The outer surface of the tubular shell at the toothed end has
annular broaching grooves and four milled slits. At its
threaded end, the anchor is provided with an unthreaded
chucking cone that has an annular break-off groove at its
base for flush mounting. Anchor shell and expander cone are
electrodeposit zinc and chromate-plated.
2.1.2 Installation: Embedment, spacing, edge distance,
and concrete requirements are shown in Tables 1 and 2. The
anchors are installed by a Model 747 Roto-Stop Hammer, by
air or electric impact hammer, or by hand. The anchor is used
as a drill in forming the hole in normal-weight concrete. After
the hole is formed, the anchor must be removed and the hole
thoroughly cleaned. The hole depth is regulated by the drill
chuck. A Red Head plug must be set into the bottom of the anchor prior to insertion in the hole. The concrete anchor must
be driven over the plug, to cause expansion of the anchor in
the hole. The chucking end of the anchor is broken off with a
hammer blow. Verification that the anchor has been installed
properly is evidenced by the fact that the anchor does not
project above the surface of the concrete and the red plug is
visible at the bottom of the hole.
2.2 ITW Ramset/Red Head Trubolt Wedge Anchor:
2.2.1 General: The Trubolt Wedge anchor is a stud bolt type
of drop-in anchor. The anchors are cold-formed or machined
from zinc-plated and chromate-dipped carbon steel, hotdipped galvanized carbon steel or stainless steel. Steel used
to produce the anchors complies with AISI C-1015 to AISI
C-1022 and AISI C-1213 carbon steels, Type 304 or Type 316
stainless steels. Hot-dipped galvanizing complies with ASTM
153 Class C requirements. The expander sleeves are fabricated from stainless steel or carbon steel meeting the require-
ments of Type 302 or AISI C-1010, respectively. Cold-formed
anchor studs are available only for the 1/4-inch-, 3/8-inch-,
1/ -inch-, 5/ -inch- and 3/ -inch-diameter (6.4, 9.5, 12.7, 15.9
2
8
4
and 19.1 mm) wedge anchors. The anchor stud is threaded
at its upper end and has a straight cylindrical section reduced
in diameter, around which the expander sleeve is formed. A
straight-tapered section enlarging to a cylindrical base acts to
increase the diameter of the expander ring as the stud is tightened in the concrete hold. The expander ring, which is formed
around the stud bolt, consists of a split-ring element with a
“coined” groove at each end. The expander ring is designed
to engage the walls of the concrete hold as the tapered portion
of the stud is forced upward against its interior.
and concrete requirements are shown in Tables 3, 4, 5 and
10. Holes must be predrilled in normal-weight or lightweight
concrete with carbide-tipped masonry drill bits manufactured
within the range of the maximum and minimum drill tip dimensions of ANSI B212.15-1994. The anchors must be installed
in holes the same nominal size as the anchor size, with a
greater depth than the length of embedment desired, but no
less than the minimum embedment. The hole must be
cleaned out prior to installation of the anchor. The anchor
must be tapped into the hole to the embedment depth desired,
but no less than the minimum embedment. A standard hexagonal nut and washer must be used over the material being
fastened and the nut tightened until the minimum installation
torque, as indicated in Tables 3 and 10, is reached.
2.3 ITW Ramset/Red Head Multi-Set II Anchor:
2.3.1 General: The Multi-Set anchors are designed to be
installed in a predrilled hole equal to the anchor diameter. The
anchor consists of a shell formed from carbon steel meeting
the minimum requirements of AISI C-1213 and an expansion
plug formed from carbon steel meeting the minimum requirements of AISI C-1010. The expansion end is divided into four
equal segments by radial slots. The expansion plug is preassembled and is cylindrical in cross section.
and concrete requirements are shown in Tables 6, 7 and 9.
Holes must be predrilled in normal-weight or lightweight concrete with carbide-tipped masonry drill bits manufactured
within the range of the maximum and minimum drill tip dimensions of ANSI B212.15-1994. The anchors must be installed
in predrilled holes, the hole depth and diameter for each anchor size being listed in Tables 6, 7 and 9. After the hole is
drilled, it is cleared of all cuttings. The anchor is set by installing the expansion shell and then driving the cone expander
with a setting tool provided with each anchor size. When the
Evaluation reports of ICBO Evaluation Service, Inc., are issued solely to provide information to Class A members of ICBO, utilizing the code upon which the report
is based. Evaluation reports are not to be construed as representing aesthetics or any other attributes not specifically addressed nor as an endorsement or recommendation for use of the subject report.
This report is based upon independent tests or other technical data submitted by the applicant. The ICBO Evaluation Service, Inc., technical staff has reviewed the
test results and/or other data, but does not possess test facilities to make an independent verification. There is no warranty by ICBO Evaluation Service, Inc., express
or implied, as to any “Finding” or other matter in the report or as to any product covered by the report. This disclaimer includes, but is not limited to, merchantability.
Page 1 of 7
Page 2 of 7
ER-1372
cone expander is driven down into the anchor, the legs of the
shell expand.
2.4 Design:
Allowable static loads are as set forth in Tables 1, 3, 6, 9 and
10. Allowable loads for anchors subjected to combined shear
and tension forces are determined by the following equation:
4.0 FINDINGS
That the ITW Ramset/Red Head fasteners described in
this report comply with the 1997 Uniform Building
Code, subject to the following conditions:
4.1
Anchor sizes, dimensions and installation are as
set forth in this report.
4.2
Allowable shear and tension loads are as set forth
in Section 2.4.
4.3
Calculations justifying that the applied loads comply with this report are submitted to the building official for approval.
4.4
Special inspection is provided as set forth in Section 2.5.
4.5
Anchors are limited to installation in uncracked
concrete, which is concrete subjected to tensile
stresses not exceeding 170 psi (1.2 MPa) as induced by external loads, deformations and interior
exposures.
2.5 Special Inspection:
4.6
When special inspection is required, compliance with Section
1701.5.2 of the code is necessary. The special inspector must
be on the jobsite continuously during anchor installation to
verify anchor type, anchor dimensions, concrete type, concrete compressive strength, hole dimensions, anchor spacings, edge distances, slab thickness, anchor embedment and
tightening torque.
Anchors are limited to nonfire-resistive construction unless appropriate data is submitted to demonstrate anchor performance is maintained in fireresistive situations.
4.7
Anchors are manufactured at Highway 12, Michigan City, Indiana, with inspections by PFS Corporation (NER-QA251).
4.8
Use of electroplated or mechanically plated carbon
steel anchors is limited to dry, interior locations.
Use of hot-dipped galvanized carbon steel is permitted in exterior-exposure or damp environments.
4.9
Except for ITW Ramset/Red Head Carbon Steel and
Stainless Steel Trubolt Wedge anchors embedded
in normal-weight concrete, as noted in Table 3, use
of anchors in resisting earthquake or wind loads is
beyond the scope of this report.
(P sńP t) 5ń3 ) (V sńV t) 5ń3 v 1
where:
Ps
=
Applied service tension load.
Pt
=
Allowable service tension load.
Vs
=
Applied service shear load.
Vt = Allowable service shear load.
The anchors cannot be subjected to vibratory loads.
Sources of such loads include, for example, reciprocating engines, crane loads and moving loads due to vehicles.
2.6 Identification:
The concrete anchors are identified by their dimensional
characteristics, the anchor size, and by the length code
stamped on the anchor. The conical-shaped expander plugs
are colored red. See Figure 1 for additional details. Length
codes are in Table 8. Packages are identified with the anchor
type and size, the manufacturer’s name and address, and the
name of the quality control agency, PFS Corporation.
3.0 EVIDENCE SUBMITTED
Data complying with the ICBO ES Acceptance Criteria for Expansion Anchors in Concrete and Masonry Elements (AC01),
dated January 1999.
4.10 The anchors are not subjected to vibratory loads,
such as those encountered by supports for reciprocating engines, crane loads and moving loads
due to vehicles.
This report is subject to re-examination in two years.
TABLE 1—ITW RAMSET/RED HEAD SELF-DRILLING ANCHOR ALLOWABLE SHEAR AND TENSION VALUES (pounds)1,3,4
f ′c = 2,000 psi
BOLT
DIAMETER
(inch)
1/
ANCHOR
DIAMETER
(inch)
4
7/
3/
8
9/
1/
2
5/
8
16
11/
16
27/
32
3/
4
1
16
f ′c = 4,000 psi
Tension
Tension
MINIMUM
EMBEDMENT
DEPTH
(inches)
With
Special
Inspection 2
Without
Special
Inspection
Shear
With
Special
Inspection 2
Without
Special
Inspection
Shear
13/32
17/32
21/32
215/32
31/4
415
785
1,150
1,510
1,985
210
395
575
755
995
295
770
920
1,605
2,495
650
1,035
1,555
2,485
3,165
325
520
775
1,240
1,585
365
650
930
1,755
2,575
For SI: 1 inch = 25.4 mm, 1 lbf = 4.45 N, 1 psi = 6.89 kPa.
1The tabulated shear and tensile values are for anchors installed in normal-weight concrete having the designated ultimate compressive strength at the time of installation.
Values have been tabulated for both ASTM A 307 and A 449 bolts installed with the device.
2These tension values are applicable only when the anchors are installed with special inspection as set forth in Section 2.5.
3The minimum concrete thickness is 11/ times the embedment depth, or the embedment depth plus three times the anchor diameter, whichever is greater.
2
4The anchors are illustrated as follows:
Page 3 of 7
ER-1372
TABLE 2—RECOMMENDED SPACING AND EDGE DISTANCE REQUIREMENTS FOR ITW RAMSET/RED HEAD SELF-DRILLING ANCHOR1
DESCRIPTION
BOLT
DIAMETER
(inch)
1/
ANCHOR
DIAMETER
(inch)
4
7/
3/
8
9/
1/
2
5/
8
16
11/
16
27/
32
3/
4
1
16
MIN.
EMBEDMENT
DEPTH
(inches)
Edge Distance
Required to
Obtain Max.
Working Load
(inches)
13/32
17/32
21/32
215/32
31/4
115/16
211/16
39/16
43/8
511/16
Min. Allowable
Edge Distance
(inches)
Load Factor Applied
= 0.85 for Tension
= 0.75 for Shear
Spacing
Required to
Obtain Max.
Working Load
(inches)
Min. Allowable Spacing
Between Anchors
(inches)
Load Factor Applied
= 0.95 for Tension
= 0.70 for Shear
37/8
53/8
71/8
811/16
113/8
115/16
211/16
39/16
43/8
511/16
1
13/
8
113/16
23/16
27/8
For SI: 1 inch = 25.4 mm.
1Linear interpolation may be used for intermediate spacing and edge distances.
TABLE 3—ITW RAMSET/RED HEAD TRUBOLT WEDGE ANCHOR ALLOWABLE SHEAR AND TENSION VALUES (pounds)1,2,4,5,6
f ′c = 2,000 psi
f ′c = 4,000 psi
Tension
ANCHOR
DIAMETER
(inches)
INSTALLATION
TORQUE
(lbf · ft)
EMBEDMENT
DEPTH
(inches)
With
Special
Insption 3
Without
Special
Inspection
1/
4
8
3/
8
25
1/
2
55
5/
8
90
3/
4
175
7/
8
250
11/8
115/16
21/8
11/2
3
4
21/4
41/8
6
23/4
51/8
71/2
31/4
65/8
10
33/4
61/4
8
41/2
73/8
91/2
51/2
8
10
295
525
565
420
870
1,200
1,165
1,165
1,335
1,645
1,645
1,765
1,780
2,745
2,745
2,380
3,665
3,665
3,485
3,650
4,675
4,535
6,835
9,035
150
265
280
210
435
600
580
580
665
820
820
880
890
1,375
1,375
1,190
1,835
1,835
1,745
1,825
2,340
2,270
3,413
4,515
1
300
11/4
500
f ′c = 6,000 psi
Tension
Shear
350
420
580
1,000
1,190
1,810
1,780
2,400
2,530
5,080
3,290
5,220
4,020
7,170
5,820
8,770
With
Special
Inspection
445
825
825
560
1,485
1,485
1,275
2,410
2,410
1,795
3,730
3,755
2,710
4,425
4,470
3,685
5,235
5,580
5,045
5,995
6,635
6,595
10,825
11,385
Tension
Without
Special
Inspection
225
410
410
280
740
740
640
1,205
1,205
900
1,865
1,880
1,355
2,210
2,235
1,840
2,620
2,790
2,520
3,000
3,315
3,300
5,410
5,695
Shear
350
420
655
1,035
1,190
1,810
1,780
2,975
3,430
5,935
4,145
7,200
5,705
9,485
7,365
11,065
With
Special
Inspection
475
825
825
710
1,530
1,530
1,760
2,705
2,705
2,430
4,095
4,095
3,325
5,065
5,895
4,355
6,090
6,090
5,295
8,315
8,315
8,410
11,385
14,075
Without
Special
Inspection
240
410
410
355
765
765
880
1,355
1,355
1,215
2,045
2,045
1,665
2,530
2,950
2,180
3,045
3,045
2,650
4,160
4,160
4,205
5,695
7,040
Shear
350
420
790
1,125
1,760
2,040
2,405
3,130
3,995
5,935
4,790
7,200
6,120
9,520
8,445
12,640
For SI: 1 inch = 25.4 mm, 1 psi = 6.89 kPa, 1 lbf · ft = 1.355 818 N · m, 1 lbf = 4.45 N.
1The tabulated shear and tensile values are for anchors installed in stone-aggregate concrete having the designated ultimate compressive strength at the time of installation.
2The holes are drilled with bits complying with ANSI B212.15-1994. The bit diameter equals the anchor diameter.
2
5Allowable static loads may be increased one-third for earthquake or wind resistance in accordance with Section 1612.3.3 of the code. No further increase is allowed.
Page 4 of 7
ER-1372
TABLE 4—RECOMMENDED SPACING AND EDGE DISTANCE REQUIREMENTS FOR TENSION LOADS
FOR ITW RAMSET/RED HEAD TRUBOLT WEDGE ANCHORS1
DESCRIPTION
ANCHOR
DIAMETER
(inches)
EMBEDMENT
DEPTH
(inches)
Edge Distance
Required to
Obtain Max.
Working Load
(inches)
1/
4
3/
8
11/8
115/16
21/8
11/2
3
4
21/4
41/8
6
23/4
51/8
71/2
31/4
65/8
10
33/4
61/4
8
41/2
73/8
91/2
51/2
8
10
2
115/16
5
1 /8
25/8
3
3
315/16
31/8
41/2
413/16
37/8
55/8
511/16
5
71/2
69/16
61/4
6
77/8
73/8
71/8
95/8
8
71/2
1/
2
5/
8
3/
4
7/
8
1
11/4
Min. Allowable
Edge
Distance
(inches)
Load Factor
Applied = 0.65
Spacing Required to
Obtain Max. Working
Load
(inches)
Min. Allowable
Spacing Between
Anchors
(inches)
Load Factor
Applied = 0.70
1
1
13/16
15/16
11/2
11/2
2
19/16
1
2 /4
27/16
115/16
213/16
27/8
21/2
33/4
35/16
31/8
3
315/16
311/16
39/16
413/16
4
33/4
315/16
37/8
33/16
51/4
6
6
77/8
63/16
9
95/8
711/16
111/4
113/8
915/16
15
131/8
121/2
12
153/4
143/4
141/4
191/4
16
15
2
115/16
5
1 /8
25/8
3
3
315/16
31/8
41/2
413/16
37/8
55/8
511/16
5
71/2
69/16
61/4
6
77/8
73/8
71/8
95/8
8
71/2
2Spacings and edge distances shall be divided by 0.75 when anchors are placed in structural lightweight concrete in accordance with Table 10.
TABLE 5—RECOMMENDED SPACING AND EDGE DISTANCE REQUIREMENTS FOR SHEAR LOADS
FOR ITW RAMSET/RED HEAD TRUBOLT WEDGE ANCHORS1
DESCRIPTION
(E)
Edge Distance
Required to
Obtain Max.
Working Load
(inches)
(E1)
Min. Edge
Distance at Which
the Load Factor
Applied = 0.60
(inches)
(E2)
Min. Edge
Distance at Which
the Load Factor
Applied = 0.20
(inches)
Min. Allowable
Spacing
Between
Anchors
(inches)
Load Factor
Applied = 0.40
ANCHOR
DIAMETER
(inches)
EMBEDMENT
DEPTH
(inches)
(See Figure 2)
(See Figure 2)
(See Figure 2)
Spacing
Required to
Obtain Max.
Working Load
(inches)
1/
4
11/8
115/16
2
115/16
15/16
1
N/A
N/A
315/16
37/8
2
115/16
3/
8
11/2
3
25/8
33/4
13/4
3
N/A
11/2
51/4
6
25/8
3
1/
2
21/4
41/8
315/16
53/16
29/16
31/8
N/A
19/16
77/8
63/16
315/16
31/8
5/
8
23/4
51/8
413/16
67/16
31/8
37/8
N/A
115/16
95/8
711/16
413/16
37/8
3/
4
31/4
65/8
511/16
85/16
33/4
5
N/A
21/2
113/8
915/16
511/16
5
7/
8
33/4
61/4
69/16
81/2
45/16
61/4
N/A
31/8
131/8
121/2
69/16
61/4
1
41/2
73/8
77/8
101/16
51/8
73/8
N/A
311/16
153/4
143/4
77/8
73/8
11/4
51/2
8
95/8
117/16
61/4
8
N/A
4
191/4
16
95/8
8
N/A = Not applicable.
Page 5 of 7
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TABLE 6—ITW RAMSET/RED HEAD MULTI-SET II ANCHOR ALLOWABLE SHEAR AND TENSION VALUES (pounds)1,2,4,5
f ′c = 2,000 psi
BOLT
DIAMETER
(inch)
ANCHOR
DIAMETER
(inch)
1/
4
3/
8
3/
8
1/
2
1/
2
5/
8
5/
8
7/
8
3/
4
1
f ′c = 4,000 psi
Tension
f ′c = 6,000 psi
Tension
Tension
MINIMUM
EMBEDMENT
DEPTH
(inches)
With
Special
Inspection 3
Without
Special
Inspection
Shear
With
Special
Inspection 3
Without
Special
Inspection
Shear
With
Special
Inspection 3
Without
Special
Inspection
Shear
1
15/8
2
21/2
33/16
420
745
825
1,375
2,070
210
375
415
685
1,035
270
790
1,145
1,860
2,620
590
950
1,460
2,160
2,370
295
475
730
1,080
1,185
300
625
875
1,385
1,920
745
1,560
2,075
2,755
3,065
375
780
1,035
1,375
1,530
325
465
600
910
1,215
1The tabulated shear and tensile values are for anchors installed in stone-aggregate concrete having the designated ultimate compressive strength at the time of installation.
Values have been tabulated for both ASTM A 307 and A 449 bolts installed with the device.
2
TABLE 7—RECOMMENDED SPACING AND EDGE DISTANCE REQUIREMENTS FOR ITW RAMSET/RED HEAD MULTI-SET II ANCHOR1
DESCRIPTION
BOLT
DIAMETER
(inch)
ANCHOR
DIAMETER
(inch)
1/
MIN.
EMBEDMENT
DEPTH
(inches)
4
3/
8
1
3/
8
1/
2
15/
1/
2
5/
8
5/
8
7/
8
3/
4
1
8
2
21/2
33/16
Edge Distance
Required to
Obtain Max.
Working Load
(inches)
Min. Allowable
Edge Distance
(inches)
Load Factor Applied
= 0.80 for Tension
= 0.70 for Shear
Spacing
Required to
Obtain Max.
Working Load
(inches)
Min. Allowable Spacing
Between Anchors
(inches)
Load Factor Applied
= 0.80 for Tension
= 0.55 for Shear
13/4
27/8
31/2
43/8
55/8
7/8
17/16
13/4
23/16
213/16
31/2
511/16
7
83/4
113/16
13/4
27/8
31/2
43/8
55/8
TABLE 8—LENGTH IDENTIFICATION CODES
LENGTH OF ANCHOR
CODE
A
B
C
D
E
F
G
H
I
J
K
L
M
Black
White
Red
Green
Yellow
Blue
Purple
Brown
Orange
N/A
N/A
N/A
N/A
LENGTH OF ANCHOR
(inches)
(mm)
CODE
(inches)
(mm)
11/2 < 2
2 < 21/2
21/2 < 3
3 < 31/2
31/2 < 4
4 < 41/2
41/2 < 5
5 < 51/2
51/2 < 6
6 < 61/2
61/2 < 7
7 < 71/2
71/2 < 8
38 < 51
51 < 63
63 < 76
76 < 89
89 < 102
102 < 114
114 < 127
127 < 140
140 < 152
152 < 165
165 < 178
178 < 191
191 < 203
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
8 < 81/2
81/2 < 9
9 < 91/2
91/2 < 10
10 < 11
11 < 12
12 < 13
13 < 14
14 < 15
15 < 16
16 < 17
17 < 18
18 < 19
203 < 216
216 < 229
229 < 241
241 < 254
254 < 267
267 < 305
305 < 330
330 < 366
366 < 381
381 < 406
406 < 432
432 < 457
457 < 483
Page 6 of 7
ER-1372
TABLE 9—ITW RAMSET/RED HEAD MULTI-SET II ANCHOR ALLOWABLE SHEAR AND TENSION VALUES (pounds)1,2,4
LOWER FLUTE OF STEEL DECK WITH
LIGHTWEIGHT CONCRETE FILL
f ′c = 3,000 psi
LIGHTWEIGHT CONCRETE
f ′c = 3,000 psi
BOLT DIAMETER
(inch)
ANCHOR
DIAMETER
(inch)
3/
8
1/
2
1/
2
5/
8
5/
8
7/
8
3/
4
1
MINIMUM
EMBEDMENT
DEPTHS
(inches) 3
With Special
Inspection 3
Without Special
Inspection
19/16
2
21/2
33/16
965
1,020
1,570
2,750
482
510
785
1,375
Tension
Tension
Shear
With Special
Inspection
Without Special
Inspection
Shear
1,105
1,410
2,610
3,945
835
800
1,490
2,045
417
400
745
1,022
1,105
1,235
1,460
2,280
1The tabulated shear and tensile values are for anchors installed in structural lightweight concrete having the designated ultimate compressive strength at the time of installation. Values have been tabulated for both ASTM A 307 and A 449 bolts installed with the device.
4Installation details are in Figure 3. Spacing and edge distances are in Table 7 as modified by Footnote 2.
TABLE 10—ITW RAMSET/RED HEAD TRUBOLT WEDGE ANCHOR ALLOWABLE SHEAR AND TENSION VALUES (pounds)1,2,4
LOWER FLUTE OF STEEL DECK WITH LIGHTWEIGHT
CONCRETE FILL
f ′c = 3,000 psi
LIGHTWEIGHT CONCRETE
f ′c = 3,000 psi
INSTALL
TORQUE
(ft.-lb.)
MINIMUM
EMBEDMENT
DEPTHS
(inches) 3
8
25
11/
1/
2
55
5/
8
90
3/
4
175
ANCHOR
DIAMETER
(inch)
3/
Tension
With Special3
Inspection
Tension
Without Special
Inspection
Shear
With Special
Inspection
Without Special
Inspection
Shear
2
530
735
265
367
930
1,060
475
710
237
355
790
1,000
21/4
3
4
3
5
900
1,180
N/A
1,500
1,490
450
590
N/A
750
745
1,760
1,655
1,730
2,310
2,320
850
1,120
1,200
1,180
1,645
425
560
600
590
822
1,345
1,655
1,610
1,375
2,285
31/4
51/4
1,790
2,225
895
1,112
3,150
3,980
1,460
1,760
730
880
2,220
N/A
3
For SI: 1 inch = 25.4 mm, 1 psi = 6.89 kPa, 1 lbf = 4.45 N.
N/A = Not applicable.
1The tabulated shear and tensile values are for anchors installed in structural lightweight concrete having the designated compressive strength at the time of installation.
4Installation details are in Figure 3. Spacing and edge distances are in Tables 4 and 5 as modified by Footnote 2.
Self-Drills
Trubolt Wedge Anchors
Multi-Set II
S (bolt size)
WS-Carbon Steel (anchor size
RM-Carbon Steel (bolt size)
length)
FIGURE 1—IDENTIFICATION SYMBOLS FOR THE VARIOUS ANCHORS
Page 7 of 7
ER-1372
1.00
S
0.60
S
0.20
E2
E1
E
FIGURE 2—LOAD FACTORS FOR TRUBOLT WEDGE ANCHOR
SHEAR LOADS AT REDUCED EDGE DISTANCES (See also Table 5)
FIGURE 3—TRUBOLT AND MULTI-SET II ANCHORS IN LIGHTWEIGHT CONCRETE (f ′c = 3,000 psi)
AND STEEL DECK WITH LIGHTWEIGHT CONCRETE FILL (f ′c = 3,000 psi)
Standard Plate Bracket
Single Bolted Connection
Double Bolted Connection
Triple Bolted Connection
Magnum Steel Push Pier Foundation Specifications
Connection Type
Allowable Capacity
*
Standard Duty Steel Pier ( 1/8" Wall Tube )
Single Bolted
Double Bolted
Triple Bolted
9 kips
19 kips
28 kips
Heavy Duty Steel Pier ( 1/4" Wall Tube )
Single Bolted
Double Bolted
Triple Bolted
*
15 kips
30 kips
43 kips
Values shown indicate the working capacities of different connections between the push pier shaft
and bracket. These capacities include a factor of safety of 1.5. The strength of the connection
between the bracket and a structure and the bearing capacity of the push pier after installation shall
be field verified through load testing.
Standard Angle Bracket
Single Bolted Connection
Double Bolted Connection
Triple Bolted Connection
Magnum Steel Push Pier Foundation Specifications
Connection Type
Allowable Capacity
*
Standard Duty Steel Pier ( 1/8" Wall Tube )
Single Bolted
Double Bolted
Triple Bolted
9 kips
19 kips
28 kips
Heavy Duty Steel Pier ( 1/4" Wall Tube )
Single Bolted
Double Bolted
Triple Bolted
*
15 kips
30 kips
43 kips
Values shown indicate the working capacities of different connections between the push pier
shaft and bracket. These capacities include a factor of safety of 1.5. The strength of the connection
between the bracket and a structure and the bearing capacity of the push pier after installation shall
be field verified through load testing.
Steel Push Pier Maximum Spacing Guide
16
This chart is applicable to Magnum Plate and Angle
Brackets. It assumes that two bolts are used to secure
the bracket to the pier, at least 6-inches of 2,000 psi
concrete cover is present over the top row of concrete
anchors, the angle bracket is attached to the structure
using grout, and that the structure is capable of
providing some moment resistance. A factor of safety
of 1.5 is incorporated.
Actual Total Dead+Live Wall Load (kip/ft)
14
12
10
Magnum Heavy Duty Push Pier
(1/4 Wall, Double Bolted)
8
Magnum Standard Duty Push Pier
(1/8 Wall, Double Bolted)
6
4
2
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
Center-to-Center Spacing (ft)
9.0
10.0
11.0
12.0
Magnum Hydraulic Ram, Channels & Bracket Mounting Boot
Magnum Hydraulic Ram, Channels and Bracket Mounting Boot
Mounted on Magnum Angle Bracket
Magnum Angle Bracket
Magnum Patented Plate Bracket
Tube for Angle and Plate Brackets
Pier Pipe and Friction Ring
Pipe to Bracket Grade 8 Bolt
MAGNUM PUSH PIER FOUNDATION
TECHNICAL REFERENCE GUIDE
MECHANICAL BENDING STRENGTH
OF PUSH PIER PIPE SHAFT
PRODUCT TESTING REPORT
July 15, 2002
TABLE OF CONTENTS
Introduction .................................................................................................................................... 3
Test Method ................................................................................................................................... 3
Pipe Shaft Bending Results ............................................................................................................ 5
Effect of Galvanization .................................................................................................................. 6
Effect of Grouting .......................................................................................................................... 8
Bending Strength of Shaft Connectors ......................................................................................... 10
-2-
INTRODUCTION
Determination of the lateral and buckling resistance of a steel push pier requires
knowledge of the mechanical bending strength of the pier shaft. Bending resistance of an empty
steel pipe can be estimated by traditional and well known engineering calculations. The bending
resistance of a grout filled pipe shaft and the effect of galvanization on bending strength is more
difficult to compute theoretically.
An investigation was conducted to measure the mechanical bending resistance of the pipe
shaft used for Magnum steel push piers. The investigation included a series of load tests on steel
pipe, grout-filled pipe, and galvanized pipe shafts. The bending strength of Magnum steel push
pier connectors were also measured. This document represents a sample of the types of testing
used by Magnum Piering to determine capacities of its steel push pier foundation products.
Other tests that have been conducted include bracket mechanical capacity, bracket concrete
anchor capacity, and full-scale field capacity. As part of a manufacturing quality assurance
program, Magnum Piering periodically tests various components of its product line. For
Magnum Piering, product testing and quality assurance is an ongoing effort. Contact Magnum
Piering headquarters for additional information and test results on any product or component.
TEST METHOD
Shaft bending tests were conducted on 5'-0" long specimens. The specimens were
mounted in a load frame with reaction supports spaced 44" apart. Deflection was measured
using a dial gage mounted at the center of the pipe specimen. A photograph of the test set-up is
shown in Fig. 1.
Some of the load tests were performed with 3 point loading wherein load was applied to a
single point at the center of the reaction supports. During these tests, it was noted that the pipe
shaft exhibited fairly significant compression at the load point. In order to evaluate the effect of
this distortion of the pipe cross-section on the bending strength, later tests were performed using
a 4 point loading technique wherein load was applied to two points between the reaction
supports. Each of the load application points was located at a distance from respective reaction
supports equal to one-third the total distance between the reaction supports. As expected, much
higher loads could be applied with considerably less pipe distortion using the 4 point load
method. However, the calculated maximum moment and measured deflection for both types of
load tests were nearly equivalent, as shown in Fig. 2. The dark or filled points on the graph
represent data obtained for the 1/8" thick wall pipe shaft, while the white or open points on the
graph represent data obtained for the 1/4" thick wall pipe shaft. As can be seen in the figure,
results for 3 point and 4 point loading for the 1/8" thick tube are identical. The load
displacement curves obtained for load tests on the 1/4" thick tube display a slight variation,
however the maximum moment and total displacement at maximum moment were nearly the
same.
-3-
Fig. 1 Pipe Shaft Bending Test Apparatus
3" O.D. Steel Tube
140,000
Applied Moment (in-lbs)
120,000
100,000
80,000
1/8 wall tube,
3 Pt. Loading
60,000
1/8 wall tube,
4 Pt. Loading
40,000
1/4 wall tube,
3 Pt. Loading
20,000
1/4 wall tube,
4 Pt. Loading
0
0
0.2
0.4
0.6
0.8
1
1.2
Displacement (in)
Fig. 2 Effect of Load Application Method
-4-
1.4
1.6
PIPE SHAFT BENDING RESULTS
Magnum steel push pier pipe shafts are manufactured from high-strength steel, seamless,
structural tubing with a 3" O.D. Two different shafts are available with 1/8" and 1/4" thick
walls. The steel comprising the structural tube has a minimum yield strength of 40 ksi and
ultimate strength of 55 ksi. Section modulus, area moment of inertia, and other properties of
Magnum steel push pier pipe shafts are given in Table 1. Area moment of inertia was computed
using the well known formula given by
π (d 4 − d 14 )
I =
64
where
I
d
d1
=
=
=
area moment of inertia,
outside diameter, and
inside diameter.
Section modulus was computed by dividing the area moment of inertia, I, by half the outside
diameter, d/2. The mechanical bending strengths of the shafts were computed by multiplying the
yield and ultimate strength of the pipe steel by the section modulus. Mechanical bending
strength is subject to variations in steel strength and tolerances in structural tube thicknesses.
Minimum theoretical mechanical bending strength is shown in Table 2.
Table 1. Magnum Push Pier Shaft Specifications
1/8" Wall Pipe
1/4" Wall Pipe
Outside Diameter (in)
3.000
3.000
Inside Diameter (in)
2.750
2.500
Area Moment of Inertia (in4)
1.17
2.06
Section Modulus (in3)
0.78
1.37
Cross-Section Area (in2)
1.13
2.16
Table 2. Magnum Push Pier Shaft Theoretical Bending Strength
1/8" Wall Pipe
1/4" Wall Pipe
Mechanical Bending Yield Strength (kip-in)
31
55
Mechanical Bending Ultimate Strength (kip-in)
43
75
Results of bending tests on non-galvanized, non-grouted pier shafts are shown in Fig. 3.
As can be seen in this figure, the measured yield and ultimate bending strength of the 1/8" thick
wall pier shaft was similar to the calculated values shown in Table 2, whereas, the measured
yield and ultimate bending strength of the 1/4" thick wall pier shaft was considerably greater
-5-
than the calculated values shown in Table 2. This suggests that the mechanical strength of the
steel used by Magnum Piering in the construction of their 1/4" thick wall steel push pier shafts
was on the order of 73 ksi yield strength and 93 ksi ultimate strength. The values given
previously were minimum values. It is suggested that design engineers continue to use
minimum values with the understanding that the strength may often be considerably greater.
Magnum Piering uses periodic hardness testing and measurement of tube wall thickness for
quality assurance.
140,000
Bending Moment (in-lbs)
120,000
1/8" Wall
1/4" Wall
100,000
Yield Point
100 kip-in
80,000
60,000
40,000
20,000
Yield Point
30 kip-in
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Deflection (in)
Fig. 3 Bending Resistance of Non-Galvanized, Non-Grouted Steel Pipe Shaft
EFFECT OF GALVANIZATION
For use in highly corrosive soils or when requested by their clients, Magnum Piering
utilizes hot-dip galvanization to increase the life expectancy of steel push pier shafts. The
process of hot-dip galvanization increases the thickness of the tubular shaft and may increase
steel strength due to heat treatment. In order to evaluate the effect of galvanization on the
bending resistance of Magnum Push Pier shafts, several specimens were tested that were
identical to the specimens described in the previous section except they were galvanized.
-6-
Results of these tests are shown in Figs. 4 and 5. As can be seen in the figures, the galvanization
process had a considerable effect on the bending strength of the 1/8" thick wall shaft and a
negligible effect on the 1/4" thick wall shaft.
140,000
120,000
100,000
80,000
60,000
40,000
Non-Galvanized
20,000
Galvanized
0
0
0.2
0.4
0.6
0.8
1
Displacement (in)
Fig. 4 Effect of Galvanization on Bending Strength of 1/8" Thick Wall Shafts
140,000
120,000
100,000
80,000
60,000
Non-Galvanized
40,000
Galvanized
20,000
0
0
0.2
0.4
0.6
0.8
1
Displacement (in)
Fig. 5 Effect of Galvanization on Bending
-7- Strength of 1/4" Thick Wall Shafts
1.2
The galvanization process increased the bending resistance of 1/8" thick wall pier shaft
by a factor of approximately 100% (i.e. 2x greater). It is left to the discretion of the design
engineer whether to utilize this strength gain in foundation design. Application of galvanization
strength gain should be weighed against the life expectancy and corrosion requirements of the
project. These strength gains likely will be reduced over time as the zinc coating is sacrificially
degraded over time.
EFFECT OF GROUTING
One method of increasing the bending resistance of steel pier shafts that can be
performed after installation is complete is filling the shaft with a high-slump cement grout. A
set of tests were performed on non-galvanized pier shaft specimens filled with a minimum 2,000
psi, 28-day compressive strength cement grout. The specimens were allowed to cure in air for
28 days prior to testing. Results of these tests are shown in Figs. 6 and 7. The results indicate
that the process of grouting increases the bending yield strength of 1/8" thick wall shafts by
approximately 75% (i.e. 1.75x greater) and the bending ultimate strength by approximately 40%
(i.e. 1.40x greater). The effect of grouting on the bending strength of 1/4" thick wall tube was
considerably less significant with negligible measured increases in the bending yield strength
and only 1% increase (i.e. 1.01x greater) in the bending ultimate strength.
140,000
Non-Grouted
120,000
Grouted
100,000
80,000
60,000
40,000
20,000
0
0
0.2
0.4
0.6
0.8
Displacement (in)
Fig. 6 Effect of Grouting on Bending Strength of 1/8" Thick Wall Shafts
-8-
1
140,000
120,000
100,000
80,000
60,000
Non-Grouted
40,000
Grouted
20,000
0
0
0.2
0.4
0.6
0.8
1
Displacement (in)
Fig. 7 Effect of Grouting on Bending Strength of 1/4" Thick Wall Shafts
With respect to the ultimate bending strength, the different effect exhibited by the grout
in 1/8" and 1/4" thick wall tubular shafts cannot be due to differences in the rigidity of the two
pipe sections. Although the 1/4" thick wall pipe shaft has a larger area moment of inertia, as
shown in Table 1, and a more steeply sloped moment-displacement curve, as shown in Fig. 2, the
displacements at the point of ultimate failure were approximately the same, as shown in Fig. 3.
A potential reason for the difference in the effect of the grout is a variation in the diameter of the
grouted column. The grout column for the 1/4" thick wall tube is 2.5", whereas the grout column
for the 1/8" thick wall tube is 2.75". Since bending strength is a function of the diameter of the
column to the 3rd power, the smaller diameter grout column should have a bending resistance
that is approximately 2/3 that of the larger diameter grout column. When this modification is
taken into account, the bending strength of the 1/4" thick wall tube should have been 15%
greater than the non-grouted tube with the same wall thickness. However, this value is still
greater than the measured result indicating that the interplay of the cement grout and the pipe
shaft is more complex and depends on additional factors.
From the foregoing set of tests, it is recommended that the bending yield strength of 1/8"
thick wall pier shafts can be increased by a factor of 75% if the shaft is grouted after installation.
Similar strength gains were not observed for the 1/4" thick wall shaft.
-9-
BENDING STRENGTH OF SHAFT CONNECTORS
Magnum Push Pier shaft sections are manufactured in 36" lengths. Sections are coupled
together by means of an internal sleeve that is fixed to one end of the section by two plug welds.
Unless otherwise specified, the sleeve is not fixed to the opposing end of the adjoining section,
as shown in Fig. 8. At the discretion of the design engineer, the sections can be welded together
in the field during installation at additional cost to the project. Welding of galvanized steel push
pier sections produces toxic gasses and should only be performed in well ventilated areas using
appropriate safety equipment. Most steel push pier installations do not require welding. Hence,
it is imperative to determine the bending resistance of the connections between the steel push
pier sections.
Fig. 8 Magnum Push Pier Connector
The bending strength of the steel push pier connector shown in Fig. 8 is expected to
depend in-part on the axial load on the pier. A conservative estimate of the bending strength of
the connector supported from buckling by the surrounding soils can be determined by examining
the bending strength of the inner sleeve.
Magnum steel push pier pipe shaft connectors are manufactured from high-strength steel,
seamless, structural tubing. The outside diameter and thickness of the sleeve depends on the
inside diameter of the main pier shaft. The steel comprising the structural tube sleeves has the
same minimum yield strength and ultimate strength of the main shaft sections. Dimensional
specifications, section modulus, area moment of inertia, and other properties of Magnum steel
push pier pipe shaft inner sleeve connectors are given in Table 3. Area moment of inertia was
again computed using the well known formula given by
π (d 4 − d 14 )
I =
64
-10-
where
I
d
d1
=
=
=
area moment of inertia,
outside diameter, and
inside diameter.
Section modulus and mechanical bending strength were computed as explained previously.
Mechanical bending strength of the inner sleeve connectors is shown in Table 4.
Table 3. Magnum Push Pier Shaft Inner Sleeve Specifications
1/8" Wall Pipe
1/4" Wall Pipe
Outside Diameter (in)
2.750
2.500
Inside Diameter (in)
2.500
2.000
Area Moment of Inertia (in4)
0.89
1.13
Section Modulus (in3)
0.65
0.90
Cross-Section Area (in2)
1.03
1.77
Table 4. Magnum Push Pier Shaft Inner Sleeve Theoretical Bending Strength
1/8" Wall Pipe
1/4" Wall Pipe
Mechanical Bending Yield Strength (kip-in)
26
36
Mechanical Bending Ultimate Strength (kip-in)
36
50
Mechanical bending tests were performed on both non-grouted and grouted steel push
pier shaft sections. The specimen dimensions, test apparatus, and procedures were as described
previously. Results of the tests are shown in Figs. 9 and 10. The measured yield and ultimate
bending strength of the 1/8" thick wall shaft connector is similar to the theoretical bending
strength of the inner sleeve as given in Table 4, whereas the measured yield and ultimate
bending strength of the 1/4" thick wall shaft connector was considerably greater than the
theoretical value given in Table 4. These results are again indicative of the typically higher
strength steel typically used by Magnum Piering for the construction of its heavy duty 1/4" thick
wall piers.
Another conclusion shown by the test data is that grouting of the 1/8" thick wall pier
section connectors significantly increased the bending strength (approx. 100% greater), whereas
grouting of the 1/4" thick wall pier section connectors produced a smaller effect (approx. 10%
greater bending strength).
-11-
140,000
Non-Grouted
120,000
Grouted
100,000
80,000
60,000
40,000
20,000
0
0
0.2
0.4
0.6
0.8
1
Displacement (in)
Fig. 9 Bending Strength of 1/8" Thick Wall Shaft Connectors
140,000
Non-Grouted
Grouted
120,000
100,000
80,000
60,000
40,000
20,000
0
0
0.2
0.4
0.6
0.8
1
Displacement (in)
Fig. 10 Bending Strength of 1/4" Thick Wall Shaft Connectors
-12-
1.2

Magnum® Steel Push PierTM Technical

Transcription

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