La Nueva AASHTO Guia de Diseno de Pavimentos...
Transcript of La Nueva AASHTO Guia de Diseno de Pavimentos...
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
AASHTO Design Guide
AASHO Road Test
50+ million loads
1.1 million load reps
Wide range of structural and
rehabilitation designs
Limited structural sections
1 climate/2 years
All climates over 20-50 years
1 set of materials
New and diverse materials
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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.
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Definitions
Mechanistic-Empirical Pavement Design Guide,
or MEPDG (now named 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.
AASHTO Interim DARWin-ME
AASHTO Interim DARWin-ME Manual of
Practice
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DG Inputs
Axle load (lb)
Materials & Construction
Structure,Joints,
Reinforcement
Climate
Damage
Dis
tre
ss
DG Process
Distress Prediction & Reliability Mechanistic Response Damage Accumulation
Time
Da
ma
ge
DG Outputs
Field Distress
Comprehensive System
Traffic
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Pavement Characterization
For Each Layer:
Physical properties
Thermal properties
Hydraulic properties
Concrete
Base
Subbase
Subgrade
Base
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New Or Reconstructed JPCP
Dense Aggregate
JPCP Reconstructed
Aggregate, Lean Conc., Asphalt
Compacted Subgrade
Natural Subgrade
CTE, Shrinkage, MR, Ec
Ec, friction
Mr, gradation,
Atterberg, thermal, &
hydraulic properties
Joint spacing = 4 m
Dowel Dia. = 27 mm
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Composite Pavement, Phoenix, AZ
Unbound Aggregate
25 cm New JPCP
HMA or Unbound Aggregate Base
Natural Subgrade
CTE, MR, Ec, shrink
Mr, gradation,
Atterberg, thermal, &
hydraulic properties
E*, Ec, Mr, friction
25 mm New HMA E*, other inputs
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Concrete Pavement Restoration California
Restoration of joint load transfer, slab replacement (past damage),
tied PCC shoulder, diamond grinding
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JPCP Overlay Georgia
JPCP Overlay
5 cm HMA Separation
Old PCC Slab (C&S)
Aggregate Base
Natural Subgrade
Bedrock
CTE, MR, Ec,
shrink
E*, other inputs
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4 m joint spacing
33 mm dowels
3.9 m outer lane width
JPCP Overlay of Existing Asphalt
Milled exist HMA layer
JPCP Overlay
Aggregate Subase
Aggregate Base
Kansas Turnpike
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Joint Faulting= f(loads, dowels, slab,
base, jt space, climate, shoulder, lane
width, zero-stress temp, built-in
gradient, …)
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, …)
Design for Performance JPCP: Models
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Slab Dimensions & Base Friction
Slab thickness: 15 to >40-cm
Slab width: conventional, widened
Tied shoulders: load transfer
Slab/Base friction: Full (typical)
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Slab Thickness Vs. Cracking
Data: AASHO Road Test
plus I-80 16 years,
12 million trucks
80
60
40
20
0
8 9 12 11 10 13
Slab thickness, cm
Sla
bs c
racked
%
DARWin-ME
20 cm 25 cm 30 cm
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Impact of Slab Width/Edge Support
0.5 m
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Transverse Joints
Need for dowels.
Benefit of larger dowels.
Transverse joint spacing.
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Need for Dowels & Diameter
Joint faulting, in
Heavy trucks (millions) 0 5 10 15 20 25
0
0.02
0.04
0.06
0.08
0.10
32 mm dowel diameter
25 mm dowel diameter
Without dowels
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Joint Spacing Effect: CA Project
Pavement Age, years
0
20
40
60
80
100
0 5 10 15 20 25 30 35
Percent Slabs Cracked
5.9 m
3.8 m
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Base & Subbase Materials, Thickness
Base types:
unbound aggregate,
asphalt,
cement/lean concrete.
Base modulus, thickness, friction with slab.
Subbase(s): unbound aggregate, lime treated soils, cement treated soils, etc.
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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.
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Temperature & Moisture Effects
Winter
Unbound Aggregate Base Mr Vs Month
0
50
100
150
200
250
1 2 3 4 5 6 7 8 9 10 11 12
Month
Res
ilie
nt
Mo
du
lus
, k
si
Winter
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Concrete Slab/Base Contact Friction
Concrete Slab (JPCP, CRCP)
Base Course (agg., asphalt, cement)
Subbase (unbound, stabilized)
Compacted Subgrade
Natural Subgrade
Bedrock
Slab/Base
Friction
Slab & Base Thick
Joint spacing
Tied shoulder, widened
Friction slab/base
Concrete Slab & Structure Inputs Flex & Comp Strength
Modulus Elasticity
Str. & Mod. gain w/time
Poisson’s Ratio
Coef. Thermal Expan.
Thermal Conductivity
Specific Heat
Built-In Thermal Grad.
Cementitious Mat’ls
W/C
Shrinkage (drying)
Unit weight
Thermal Structural
Mix Properties
Design
Fatigue Capacity
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Concrete Coefficient of Thermal Expansion
0
5
10
15
20
0 5 10 15 20 25 30
Age, years
Perc
en
t sla
bs c
racked
6.5x10-6/F
6.0x10-6/F
5.5x10-6/F
5.0x10-6/F Limestone
Granite, Sandstone,
Quartzite
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Climate (temperature, moisture, solar rad., humidity, wind)
Integrated Climatic Model (ICM)
User identifies local weather stations:
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.
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Climatic Factors Slab Curling/Warping
Positive temp. gradient
Bottom Up Cracking
Negative temp. gradient
& shrinkage of surface
Top Down Cracking
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Slab Built-In
temperature
gradient during
construction at
time of set
(solar radiation)
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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
Vehicle Class Distribution
Level 1 – Site-
specific distribution
Level 2 – Distribution
for given highway
class
Level 3 – DARWin-
ME Truck Traffic
Class (TTC)
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Axle Configuration Factors
Axle Width
Axle Spacing
Tire Pressure (hot inflation OR measured
under operating conditions)
Dual Tire Spacing
Wheelbase
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Traffic Wander
x
Direction of traffic
Pavement Shoulder
x
Direction of traffic
Pavement Shoulder
Typical Values
X (mean) = 45.7 cm
X (SD) = 25.4 cm
Truck Wander
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Design Reliability
Design life: 1 to 100 years.
Select design reliability: 50 to 99 percent
Transverse cracking
Joint faulting
Smoothness, IRI
Standard error based on prediction error
of distress & IRI from hundreds of field
pavement sections.
34 National Field Calibration Concrete Sections
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Example Prediction of Transverse Fatigue Cracking
Example Prediction Joint Faulting
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Example Prediction IRI IR
I, in
/mi
40
80
120
160
200
240
280
320
Age, months
0 24 48 72 96 120 144 168 192 216 240
SHRPID=4_0262
GENERAL INFO
RUN PROGRESS
PAVEMENT STRUCTURE
LAYER PROPERTIES
PERFORMANCE
EXPLORER WINDOW
ERROR LIST
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DARWin-ME 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
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Compare output distress & IRI
0
40
80
120
160
200
240
280
320
360
400
0 2 4 6 8 10 12 14 16 18 20 22
Pavement age, years
IRI,
in
/mil
e
IRI at 50%
IRI at 95%
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Does design meet performance criteria?
Distress
Target
Reliability
Target
Distress
Predicted
Reliability
Predicted Acceptable
172 95 130 83.15 Fail
15 95 1.6 99.98 Pass
0.15 95 0.089 93.13 Fail
Transverse Cracking (% slabs cracked)
Mean Joint Faulting (in)
Performance Criteria
Terminal IRI (in/mi)
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Reliability Level Impact for JPCP Project
Design Reliability Vs Slab Thickness
7
8
9
10
11
12
13
14
15
60 80 90 95 99 99.9
Design Reliability
Sla
b T
hic
kn
ess, in
Recommended Design Reliability Criteria: Arizona
Performance
Criteria
Divided
Highways,
Freeways,
Interstates
Non Divided,
Non Interstate,
10,000+ ADT
2001 –
10,000 ADT
501-2,000
ADT
< 500
ADT
Design
Reliability 97% 95% 90% 80 75
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Modify Trial Design as Needed
Here is where experience and knowledge of fundamental concepts of pavement behavior and performance counts!
Examples:
Too high joint faulting? Increase dowel diameter
Too high cracking? Increase thickness, shorter joint spacing, add tied PCC shoulders, treated base
Too high IRI? Reduce distress, specify smoother construction
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DARWin-ME Analysis Capabilities
New Design: several alternatives
Rehabilitation Design: several alternatives
“What if” questions
Evaluation: forensic analysis
Construction deficiencies: impacts on life, $
Truck size and weight: cost allocation
Acceptance quality characteristics: impact on performance, $
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Key Benefits of DARWin-ME 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 (IRIi, fault, crack, spall) Faulting
Cracking
Directly considers Performance