Simplified Steel Stair Design for Commercial

Transcription

Simplified Steel Stair Design for
Commercial and Institutional Buildings
Collaborating with steel stair fabricators during the design
of commercial and institutional buildings promotes
integrated practice and produces streamlined results.
Provided by: Lapeyre Stair
Written by: Peter J. Arsenault, FAIA, NCARB, LEED-AP
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McGraw-Hill Construction is a registered provider with The
American Institute of Architects Continuing Education
System. Credit earned on completion of this program will be
reported to CES records for AIA members. Certificates of
completion for non-AIA members are available on request.
This program is registered with the AIA/CES for continuing
professional education. As such, it does not include content
that may be deemed or construed to be an approval or
endorsement by the AIA of any material of construction or
any method or manner of handling, using, distributing, or
dealing in any material or product.
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This presentation is protected by US and international copyright
laws. Reproduction, distribution, display and use of the
presentation without written permission of the speaker is strictly
prohibited.
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After participating in this presentation, you will be able to:
•!
Identify and recognize the overall parameters, general code
requirements, and preliminary design outcomes in a building stair
design.
•!
Determine the specific requirements and options for stair treads,
risers, and landings in building stair systems.
•!
Differentiate between the specific requirements and options for stair
guards and handrails in commercial and institutional buildings.
•!
Formulate construction specifications for steel stair systems
working in concert with recognized standards and specialty
fabricators.
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Section 1: General Stair Design Overview
Section 2: Stair Design Specifics: Treads,
Risers and Landings
Section 3: Stair Design Specifics: Guards
and Handrails
Section 4: Steel Stair Construction Specifications
Section 1
General Stair Design Overview
The Architect will typically determine
the following:
•! Building Parameters
•! Applicable Codes and Standards
•! Basic Design Decisions
Section 1:
General Definitions:
Stair: “A change in elevation, consisting of one or
more risers.” (International Building Code) (IBC)
Step: “A rest for the foot in ascending or
descending as one of a series of structures
consisting of a riser and tread.”
(Merriam Webster Dictionary)
Stairway: “One or more flights of stairs, either exterior or
interior, with the necessary landings and platforms
connecting them, to form a continuous and uninterrupted
passage from one level to another.” (IBC)
Section 1:
Building Parameters:
The Architect working in concert with the Owner will
always determine the overall building criteria and
parameters that affect the general and specific details
of stair design.
Section 1:
1. Building Type: Fundamentally, determining if the
building is classified as a commercial, institutional,
multi-family, mixed use, or other building application.
Each type has obvious differences in use and code
requirement calculations
Section 1:
2. Floor to floor or landing heights
The physical vertical dimension that each
building stair is servicing needs to be
determined and finalized
Generally, steel stair systems service up to 12’
vertical rise maximum before connecting
to a landing or level
Section 1:
3. Overall building design requirements
The Architect and other design professionals determine the
overall design standards for the building including:
•!
Aesthetics/Appearance
•!
Durability
•!
Materials
•!
Function
Section 1:
Applicable Codes and Standards
Virtually all of the specific dimensions of most stair
components and spaces are governed by a code
or standard.
Materials, surface texture, and other product
specific items are also subject to regulation.
Section 1:
1. International Building Code (IBC)
Means of Egress: “A continuous and unobstructed path of vertical
and horizontal egress travel from any occupied portion of a
building or structure to a public way.” (IBC)
Enclosed stairways are typically a critical part of a means of
egress and exit and regulated with many very prescriptive details.
Section 1:
1. International Building Code (IBC)
Some recent updates include details of:
•! Minimum egress width
•! Open riser changes
•! Handrail graspability
•! Required locations for guards
•! Limitations on guard openings
•! Luminous markings in egress path
•! Required areas of refuge
Section 1:
2. Handicapped Accessibility Requirements
Area of Refuge: “An area where persons unable to use
stairways can remain temporarily to await instruction or
assistance during emergency evacuation.” (IBC)
Stairways often include these areas within their enclosure.
Section 1:
2. Handicapped Accessibility Requirements
IBC, ANSI 117.1 and ADA all impose
requirements for stairways and components to
be accessible for non-wheelchair based
handicaps including:
•! Treads and Risers
•! Nosings
•! Handrails
Section 1:
3. General Safety Standards
Workplace safety governed by OSHA standards that
address stairs, handrails, guardrails, and slip
resistance.
ASTM Standard F1637 addresses “Standard Practice
for Safe Walking Surfaces.”
Section 1:
General Design Decisions
Architects and Designers determine:
•! Stair Configuration to fit with building
design: straight run, switch back, angled,
scissor stair, custom, etc.
•! Presence of other allowable items in
stairwells such as sprinklers, standpipes,
openings, etc. and clearances required
•! Applicable Code and Standard
requirements to determine design features
such as occupancy load for stair, stair
width and handicapped accessibility
requirements.
Section 1:
General Design Decisions
Steel Stair Fabricators/Manufacturers can use the General
Design Decisions from architects to develop the specific
details of the fabricated stair design.
In the spirit of integrated practice, the fabricator or
manufacturer can provide a preliminary or “trial” shop
drawing for the architect’s review and input to coordinate the
overall building design and stair design together.
Section 2
Stair Design Specifics: Treads, Risers, and Landings
The Stair fabricator / manufacturer can provide the specialty
details of the following under the direction of the Architect:
•! Treads
•! Risers
•! Landings
•! Nosings
Section 2:
Treads
1. Tread Definition:
“The upper horizontal part of a
step” (Merriam-Webster
Dictionary)
Codes and standards assume
common understanding and don’t
define differently.
Section 2:
Treads
2. Specific Code and Standard Requirements for
Treads:
Depth: 11” minimum with less than 3/8” variation
between treads in a single run of stairs (IBC)
Width: to match stair width requirements (IBC)
Profile: Leading edge or nosing shall be less than !”
curve or bevel (ANSI 117.1)
Slip resistance: Stable, planar, level, flush & slip resistant
(ASTM F1637)
Section 2:
Treads
3. Tread Design Options:
•! Steel pan filled with concrete on site
•! Fabricated smooth plate steel
•! Fabricated diamond plate patterned steel
•! Primed steel for separate field finish
•! Pre-finished in standard or custom colors
•! Galvanized steel
Section 2:
Risers
1. Riser Definition:
“The upright member between two stair
treads” (Merriam-Webster Dictionary)
Codes and standards also assume
common understanding and don’t
define differently.
Section 2:
Risers
2. Specific Code and Standard Requirements for Risers:
Height: 4” – 7” with less than 3/8” variation along a run of
stairs (IBC)
Open or closed: Closed most common and required for
accessible stairs (ANSI 117.1). Open risers allowed only in
limited situations (IBC & OSHA)
Flat or sloped: vertical or up to 30 degrees slope (ANSI 117.1)
Section 2:
Risers
3. Riser Design Options:
•! Open or closed
•! Flat or sloped if closed
•! Material choice
•! Pre-finished or field-finished
Section 2:
Landings
1. Landings Definition:
“A level part of a staircase (as
at the end of a flight of
stairs).” (Merriam-Webster
Dictionary)
Codes and standards assume
understanding and don’t define
differently.
Sometimes referred to as a
stair platform
Section 2:
Landings
2. Specific Code and Standard
Requirements for Landings:
Location: Required at the top and bottom of
each stairway (IBC)
Width: to match stair width requirements (IBC)
Slip resistance: Stable, planar, level, flush, and
slip resistant (ASTM F1637)
Stair level identification (ANSI 117.1)
Section 2:
Landings
3. Landing Design Options (could be same or different
than treads)
•! Steel pan filled on site with concrete
•! Fabricated smooth plate steel
•! Fabricated diamond plate patterned steel
•! Primed steel for field-finish
•! Galvanized steel
Section 2:
Nosings
1. Nosing Definition:
“The leading edge of
treads of stairs and of
landings at the top of
stairway flights” (IBC)
Section 2:
Nosings
2. Specific Code and Standard Requirements for
Nosings:
Projection from vertical: 1-1/4” (IBC ) or 1-1/2” max.
(ANSI 117.1)
Differentiation: Visual contrast across front 2 inches of
tread. (ANSI 117.1, ASTM F1637)
Slip resistance: tactile difference along nosings are a
common safety feature (ASTM F1637)
Section 2:
Nosings
3. Nosing Design Options (could be same or
different than treads and landings)
•! Integral to stair tread
•! Integral to stair riser
•! Additional add-on treatment
Section 3
Stair Design Specifics: Guards and Handrails
The Stair fabricator / manufacturer can provide the
specialty details of the following under the direction
of the Architect:
•! Guards
•! Handrails
•! Stringers
Section 3:
Guards
1.!Guard Definition:
“A building component or a system
of building components located at
or near the open sides of elevated
walking surfaces that minimizes
the possibility of a fall from the
walking surface to a lower
level” (IBC)
Section 3:
Guards
2. Specific Guard Code and Standard Requirements:
Required: Anywhere above 30” above floor or grade
below (IBC)
Height: 42” high measured vertically above the leading
edge of the tread or adjacent walking surface. (IBC)
Opening restrictions: a 4” sphere shall not pass through
any opening up to a height of 34 inches or an 8” sphere
between height of 34 – 42 inches (IBC)
Section 3:
Guards
3. Guard Design Options
Architects need to specify if guards are needed or if
stairway walls are present and negate the need:
•! One side
•! Both sides
•! Neither side
Section 3:
Guards
3. Guard Design Options
•! Rails or pickets
•! Solid filler panels
•! Wire mesh panels
•! Primed for field-finish
•! Galvanized
•! Welded or bolted – pre-assembled or field assembled
Section 3:
Handrails
1.!Definition:
“A horizontal or sloping
rail intended for grasping
by the hand for guidance
or support” (IBC)
Section 3:
Handrails
2. Specific Handrail Code and Standard
Requirements:
Required: On both sides of all stairs and
ramps. Intermediate (center) rail if more
than 60” stair width (IBC & ANSI 117.1)
Continuity: Handrails shall be continuous
without interruption at ends or supports (IBC &
ANSI 117.1)
Height: Uniform height that is no less than 34”
and no higher than 38” measured vertically
above stair tread nosing (IBC & ANSI 117.1)
Section 3:
Handrails
2. Specific Handrail Code and Standard Requirements
(cont’d):
Graspability for Circular handrails: Outside diameter of at
least 1.25 inches but less than 2 inches. (IBC & ANSI 117.1)
Graspability for Non-Circular handrails: Perimeter dimension
of at least 4 inches but less than 6.25 inches and maximum
cross section of 2.25 inches. (IBC & ANSI 117.1)
Section 3:
Handrails
2. Specific Handrail Code and
Standard Requirements (cont’d):
Clearance: 1-1/2 inches minimum
clearance between handrail and wall or
guard (IBC & ANSI 117.1)
Surfaces: Smooth with rounded edges
(IBC & ANSI 117.1)
Handrail Extensions: 12 inches or depth
of tread past the last top and bottom
tread (IBC & ANSI 117.1)
Section 3:
Handrails
3. Handrail Design Options
Architects need to specify if handrails are intended
to be installed as:
•! Guard mounted
•! Stair mounted
•! Wall mounted
Section 3:
Handrails
3. Handrail Design Options
•! Primed for field finish
•! Galvanized
•! Pre-assembled or field assembled
•! Welded or bolted
Section 3:
Stringers
1. Stringer Definition:
“The structural member that
supports the treads and
risers.”
Section 3:
Stringers
1. Stringer Design Options:
•! Flat Plate
•! C- Channel
•! Tube
•! Z-Channel
Section 3:
Stringers
3. Structural Requirements for Stringers
•! Size and Number of stringers are determined by the
stair design and load requirements
•! Center stringers may be required for wide stairs in
excess of 6’0” in width (NAAM 4.4)
•! Stair manufacturer can help determine the
appropriate stringer sizes to meet design
requirements
Section 4
Steel Stair Construction Specifications
The Stair fabricator / manufacturer and
the Architect can work together to
fashion appropriate specifications for
the construction and installation of the
steel stair system.
Section 4:
Part 1: General
Relevant Fabrication standards:
•! AISC
Manual of Steel Construction
Code of Standard Practice
•! ASTM
Select relevant standard based on type of steel
product and treatment
•! NAAM
510-92 Metal Stairs Manual
ANSI/NAAM Metal bar Grating Manual
Section 4:
Part 1: General
Performance and Construction Requirements:
•! Components to meet concentrated and distributed
load requirements – code minimum or above
•! Fabrication of components to be of single piece
material
•! Specify welded or bolted conditions where
appropriate
Section 4:
Part 1: General
Submittals
•! Manufacturer’s installation instructions
•! Dimensioned drawings for approval
before fabrication
•! Full shop drawings
•! In the spirit of integrated practice, the submittal
process can be drastically simplified if the stair
fabricator provides “trial drawings” during design
for coordination and integration in building
Section 4:
Part 1: General
Delivery, Storage and Handling
•! Reference AISC Code of Standard
Practice, Sections 6 and 7
•! Clean, dry, location away from
damaging chemicals or substances
•! Lay out on firm material to avoid bending
•! Do not stack
•! Protect finishes
Section 4:
Part 2: Products
Manufacturer
•! Select a single manufacturer for all components for a
complete, coordinated system
•! Assure availability to project location
Section 4:
Part 2: Products
Materials
•! Steel stair components
•! Brackets or mounting devices
•! Fasteners
•! Miscellaneous materials
Section 4:
Part 2: Products
Finishes
Pick one for each component.
Powder coat baked enamel:
•!Gray primer
•!Safety yellow paint
•!Standard or custom colors
•!Hot dip galvanized
Section 4:
Part 2: Products
Fabrication
Per final approved shop drawings,
determine assembly type:
•! Welded
•! Field bolted
•! Pre-assembled
•! Partially assembled
Section 4:
Part 2: Products
Packaging
Pack and ship in a manner to protect the final products
and minimize the potential for damage during shipping and
handling
Section 4:
Part 3: Execution
Preparation
•! Coordinate with other trades and work
•! Weather and operations protection
•! Verify enclosure dimensions
•! Verify substrate
•! Make any needed corrections prior to stair installation
Section 4:
Part 3: Execution
Installation
•! Field check steel components
•! Handle to avoid bending or deforming
•! Inspect, replace, or repair any damaged pieces
•! Pre-assemble per instructions
•! Prepare mounting holes
•! Install square, level, and plumb
•! Tighten all fasteners to torque level
Section 4:
Part 3: Execution
Cleaning
•! Touch up finishes
•! Clean finished assembly
Section 4:
Final Installation Examples
Section 4:
Section 4:
Thank you!
Please take the test to receive your
AIA credits
This concludes the
American Institute of Architects
Continuing Education System Program
www.lapeyrestair.com

Simplified Steel Stair Design for Commercial

Transcription

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