La Nueva AASHTO Guia de Diseno de Pavimentos Hormigon

La Nueva AASHTO Guia de Diseno de Pavimentos Hormigon

La Nueva AASHTO Guia de
Diseno
de Pavimentos Hormigon
Michael I. Darter
Emeritus Prof. Civil Engineering, University of Illinois
&
Applied Research Associates, Inc. USA
October 2012
Cordoba, Argentina
Current AASHTO vs. Current Needs
Wide range of structural and
rehabilitation designs
50+ million loads
Limited structural sections
1.1 million load reps
AASHO Road Test
AASHTO Design Guide
1 climate/2 years
All climates over 20-50 years
1 set of materials
New and diverse materials
1996: AASHTO Decided New Design Needed
„
„
„
„
1998-2007: Development of new AASHTO
design procedure.
2007: AASHTO Interim Mechanistic-Empirical
Pavement Design Guide approved.
2011: New software DARWin-ME.
Implementation by many States, Canadian
Provinces, & Others since 2004.
3
Definitions
„
„
„
„
Mechanistic-Empirical Pavement Design
Guide, or MEPDG (DARWin-ME).
Fundamental engineering mechanics as basis
for modeling (stress, strain, deformation,
fatigue, cumulative damage, etc.).
Empirical data from field performance.
M-E “Marriage” of theory and data.
4
AASHTO Interim MEPDG
„
„
Version 1.000 April 2007 on Transportation
Research Board web site: www.trb.org/mepdg
AASHTO Interim MEPDG Manual of
Practice
Climate
Traffic
Materials & Construction
Structure,Joints,
Reinforcement
Comprehensive System
DG Inputs
wAxle load (lb)
DG Outputs
Damage
Distress
DG Process
Mechanistic Response
Time
Damage Accumulation
Field Distress
Damage
Distress Prediction & Reliability
6
Pavement Characterization
For Each Layer:
„
Physical properties
„
Thermal properties
„
Hydraulic properties
Base
Concrete
Base
Subbase
Subgrade
7
New Or Reconstructed JPCP
Joint spacing = 4 m
Dowel Dia. = 27 mm
JPCP Reconstructed
Aggregate, Lean Conc., Asphalt
CTE, Shrinkage, MR, Ec
Ec, friction
Dense Aggregate
Compacted Subgrade
Mr, gradation,
Atterberg, thermal, &
hydraulic properties
Natural Subgrade
8
Composite Pavement, Phoenix, AZ
25 mm New HMA
E*, other inputs
25 cm New JPCP
CTE, MR, Ec, shrink
HMA or Unbound Aggregate Base
E*, Ec, Mr, friction
Unbound Aggregate
Mr, gradation,
Atterberg, thermal, &
hydraulic properties
Natural Subgrade
9
Concrete Pavement Restoration
Restoration of joint load transfer, slab replacement (past damage),
tied PCC shoulder, diamond grinding
10
JPCP Overlay
JPCP Overlay
5 cm HMA Separation
CTE, MR, Ec,
shrink
E*, other inputs
Old PCC Slab (C&S)
Aggregate Base
Natural Subgrade
Bedrock
11
MEPDG Analysis Results
Uniform (2 lanes)
JPCP Overlay
Milled exist HMA layer
Aggregate Base
Aggregate Subase
4 m joint spacing
33 mm dowels
3.9 m outer lane width
12
Design for Performance JPCP: Models
IRI= f(IRIi, faulting, cracking,
spalling, soil( P-200), age, FI )
Transverse Crack= f(loads, slab,
base friction, subgrade, jt space,
climate,shoulder, lane width,
built-in temp grad, PCC strength,
Ec, shrink, …)
Joint Faulting= f(loads, dowels, slab,
base, jt space, climate, shoulder,
lane width, zero-stress temp, built-in
gradient, …)
13
Slab Dimensions & Base Friction
„
„
„
„
Slab thickness: 15 to >40-cm
Slab width: conventional, widened
Tied shoulders: load transfer
Slab/Base friction: Full (typical)
14
Slab Thickness Vs. Cracking
Slabs cracked %
80
Data: AASHO Road Test
plus I-80 16 years,
12 million trucks
60
40
20
MEPDG
0
8
9
10
11
12
13
Slab thickness, in
15
Impact of Slab Width/Edge Support
0.5 m
16
Transverse Joints
„
„
„
Need for dowels.
Benefit of larger dowels.
Transverse joint spacing.
17
Need for Dowels & Diameter
Joint faulting, in
0.10
Without dowels
0.08
0.06
1 in dowel diameter
0.04
1.5 in dowel diameter
0.02
0
0
5
10
15
20
25
Heavy trucks (millions)
18
Joint Spacing Effect: CA Project
Percent Slabs Cracked
w100
w80
Measured (12-ft)
Predicted (12-ft)
Measured (19-ft)
Predicted (19-ft)
w60
w40
w20
w0
w0
w5
w10
w15
w20
w25
w30
w35
wPavement Age, years
19
Base & Subbase Materials, Thickness
„
Base types:
z
z
z
„
„
unbound aggregate,
asphalt,
cement/lean concrete.
Base modulus, thickness, friction with
slab.
Subbase(s): unbound aggregate, lime
treated soils, cement treated soils, etc.
20
Material Characterization
Material modulus is
a key property of
each layer
Resilient Modulus Mr of
Unbound Materials & Soils
Dynamic Modulus E*
of HMA base
Static Modulus of Concrete Slab
& Cement-Treated Base
21
Subgrade / Embankment / Bedrock
„
„
„
„
„
Soil types: all AASHTO classes with
defaults for gradation, PI, LL, resilient
modulus.
Subgrade resilient modulus: changes due
to temperature & moisture over year.
Lime and cement treated soils.
Thick granular layers.
Bedrock layer.
22
5.Review computed outputs
wUnbound Aggregate Base Mr Vs Month
Resilient Modulus, ksi
w250
Winter
w200
w150
w100
w50
w0
w1
w2
w3
w4
w5
w6
w7
w8
w9
w10
w11
w12
Month
23
Concrete Slab/Base Contact Friction
Concrete Slab (JPCP, CRCP)
Base Course (agg., asphalt, cement)
Slab/Base
Friction
Subbase (unbound, stabilized)
Compacted Subgrade
Natural Subgrade
Bedrock
24
Concrete Slab & Structure Inputs
Coef. Thermal Expan.
Thermal Conductivity
Specific Heat
Built-In Thermal Grad.
Flex & Comp Strength
Modulus Elasticity
Str. & Mod. gain w/time
Poisson’s Ratio
Thermal
Structural
Fatigue
Capacity
Mix
Properties
Cementitious Mat’ls
W/C
Shrinkage (drying)
Unit weight
Design
Slab Thick
Joint spacing
Tied shoulder, widened
Friction slab/base
Concrete Properties
„
Elastic Modulus, “E”
z
z
„
Flexural Strength, modulus
of rupture
z
z
z
„
Third point loading test
ASTM C 78
Change over time
Concrete coefficient of
thermal expansion
z
„
ASTM C 469
Change over time
AASHTO TP60-00
Concrete shrinkage
z
z
ASTM C 157
Change over time
26
Percent slabs cracked
Concrete Coefficient of Thermal Expansion
20
6.5x10-6/F
15
Granite,
Sandstone,
Quartzite
10
6.0x10-6/F
5
5.5x10-6/F
Limestone 5.0x10-6/F
0
0
5
10
15
20
25
30
Age, years
27
Climate (temperature, moisture, solar rad., humidity, wind)
„
Integrated Climatic Model (ICM)
z
User identifies local weather stations
(851 available in US):
¾
¾
¾
z
z
z
z
Hourly temperature, Precipitation
Cloud cover, Relative ambient humidity
Wind speed.
User inputs water table elevation.
ICM Computes temperatures in all
pavement layers and subgrade.
ICM Computes moisture contents in
unbound aggregates and soils.
ICM Computes frost line.
28
Climatic Factors Slab Curling/Warping
Positive temp. gradient
Negative temp. gradient
& shrinkage of surface
Bottom Up Cracking
Top Down Cracking
29
Slab Built-In
temperature
gradient during
construction at
time of set
(solar radiation)
30
Impact of Traffic Loading
„
„
„
„
„
„
„
Vehicle volume, growth & classification
Single, tandem, tridem, quad axle load
distributions
Monthly vehicle distribution
Hourly load distribution
Lateral lane distribution
Tire pressure
Tractor wheelbase
31
Vehicle Class Distribution
ƒ
ƒ
ƒ
Level 1 – Utah sitespecific distribution
Level 2 – Utah
distribution for given
highway class
Level 3 – DARWinME Truck Traffic
Class (TTC)
Axle Configuration Factors
Wheelbase
Tire Pressure
(hot inflation
OR measured
under operating
conditions)
Axle
Spacing
Dual Tire
Spacing
Axle Width
33
Traffic Wander
Truck Wander
Pavement
Shoulder
x
Direction of traffic
Typical Values
X (mean) = 457 mm (18
in)
X (SD) = 254 mm (10 in)34
Design Reliability
„
„
Design life: 1 to 100 years.
Select design reliability: 50 to 99 percent
z
z
z
„
Transverse cracking
Joint faulting
Smoothness, IRI
Standard error based on prediction error
of distress & IRI from hundreds of field
pavement sections.
35
Field Calibration Concrete Sections
36
Example Prediction of Transverse Fatigue Cracking
37
Percent Slabs Cracked
LTPP 12-3811, FL
100
80
60
40
20
0
0
5
10
15
20
25
30
35
Pavement Age, years
Measured
Predicted
38
Example Project Joint Faulting
39
Example: Wisconsin JPCP, US 18
25-cm JPCP, CTE=11/C, Width=4-m
Random Jt Space: 4 to 6-m
No Dowels
10-cm Unbound
Aggregate Base (2.3% fines)
Natural Subgrade
Bedrock
40
WS JPCP Measured Vs Predicted
14 years, 5.5 million trucks
Distress
Existing JPCP
Slab cracking
4-m = 0%
6-m = 38%
Joint faulting
1.75-mm
IRI
2.3 m/km
41
What If . . . Modify the JPCP Design?
„
If we could go back and “modify” the original
design, what would we do?
z
z
Add 27-mm diameter dowel bars at transverse joints.
Use of 5-m uniform joint spacing rather than 4-6-m
random spacing.
42
WS JPCP Measured Vs Predicted
14 years, 5.5 million trucks
Distress
Existing JPCP
MEPDG Prediction
Slab cracking
4-m = 0%
6-m = 38%
4-m = 0%
6-m = 60%
Joint faulting
1.75-mm
2.0-mm
IRI
2.3 m/km
2.3-m
43
Examples Of
Concrete Pavement Design
Process
Software sold by
AASHTO.
www.aashto.org
44
wGENERAL
INFO
wEXPL
ORER
WINDO
W
wPAVE
MENT
STRUC
TURE
wANALYSIS
PARAMETER
S
wLAYER
PROPERTIES
wERROR
LIST
wRUN
wPROG
RESS
Rigid Pavement Design Process
1. Trial design selection
2. Estimate inputs
3. Run software
4. Review computed outputs
5. Compare distresses & IRI with criteria
6. Design Reliability met?
7. Modify trial design as needed
46
Compare output distress & IRI
400
360
320
IRI, in/mile
280
240
IRI at 95%
200
160
120
IRI at 50%
80
40
0
0
2
4
6
8
10
12
14
16
18
20
22
Pavement age, years
47
Does design meet performance criteria?
Performance Criteria
Terminal IRI (in/mi)
Transverse Cracking (% slabs cracked)
Mean Joint Faulting (in)
Distress
Target
Reliability
Target
Distress
Predicted
172
15
0.15
95
95
95
130
1.6
0.089
Reliability
Predicted Acceptable
83.15
99.98
93.13
Fail
Pass
Fail
48
LTPP 0214 SPS2, W of Phoenix,
MP 109, 32 Million Trucks
Design Reliability
„
Reliability design methodology in ME-PDG is
practical to use (not complicated). But, requires
consideration of more than thickness for JPCP.
z
JPCP: thickness, dowel diameter, & joint spacing must
be considered together. Other factors may be varied
as well.
50
Reliability Level Impact for JPCP Project
Slab Thickness, in
Design Reliability Vs Slab Thickness
15
14
13
12
11
10
9
8
7
60
80
90
95
99
99.9
Design Reliability
51
Recommended Design Reliability Criteria: Arizona
Divided
NonDivided,
Performance Highways,
2001–
NonInterstate,
Freeways,
Criteria
10,000ADT
10,000+ADT
Interstates
Design
Reliability
97%
95%
90%
5012,000
ADT
<500
ADT
80
75
Modify Trial Design as Needed
„
„
Here is where experience and knowledge of
fundamental concepts of pavement
behavior and performance counts!
Examples:
z
z
z
Too high joint faulting? Increase dowel diameter
Too high cracking? Increase thickness, shorter
joint spacing, add tied PCC shoulders
Too high IRI? Reduce distress, specify
smoother construction
53
MEPDG Analysis Capabilities
„
„
„
„
„
„
Design & Rehabilitation: many alternatives
“What if” questions
Evaluation: forensic analysis
Construction deficiencies: impacts on life, $
Truck size and weight: cost allocation
Acceptance quality characteristics: impact on
performance, $
54
Key Benefits of M-E Design
„
„
„
Allows design for longer life pavements (checks for
early distress)
Allows designer to quantify costs & benefits
Allows designer to optimize the design (biggest
bang for $)
IRI (IRI , fault, crack, spall)
i
Faulting
Cracking
55