Diseño de Pavimentos de Hormigón para alcanzar larga Vida útil

Comments

Transcription

Diseño de Pavimentos de Hormigón para alcanzar larga Vida útil
Diseño de Pavimentos de
Hormigón para alcanzar larga
Vida útil con Confiabilidad
Michael I. Darter
Emeritus Prof. Civil Engineering, University of Illinois
&
Applied Research Associates, Inc. USA
October 2012
Cordoba, Argentina
Oldest Concrete Pavement USA
Ohio 1891 [121 years]
Design Life for HMA & PCC was 20 years
Utah Survival Curves – I-15 (100+ miles)
Percent Sections Survived
100
90
80
HMA
70
PCC
60
50
40
30
20
10
0
0
5
10
15
20
Age, years
25
30
35
40
Long Life Concrete Pavement
Structural design
„ Materials durability
„ Construction quality
„ Design Life = 40 to 100 years!
All are equally important to long life
concrete pavement
„
4
Long Life Concrete Pavement
„
Structural design
z Fatigue life of
concrete slab must
be minimized
z AASHTO
DARWin-ME
Design Procedure
Useful
5
Long Life Concrete Pavement
„
Materials
durability
z
z
z
Ice crystals
Concrete slab
Dowels &
Tiebars
Base course
6
Long Life Concrete Pavement
„
Construction quality
z
z
z
Concrete quality
Dowels and tiebar placement accurate
Base course quality
7
Construction Problems
„
„
„
„
Dowel placement
Forming of joints
Tie bar placement
Consolidation of PCC
Others
Transverse Joint
„
Poor Dowel
Alignment
Good Dowel
Alignment
Use of AASHTO DARWin-ME for Structural Design
of Long Life Concrete Pavement
„
Site Conditions
z
z
z
Climate: concrete & base durability
Existing Pavement / Subgrade: support
Traffic: loadings
9
Use of AASHTO DARWin-ME for Structural Design
of Long Life Concrete Pavement
„
At a given site:
z
z
z
z
z
Slab dimensions: Length, width, thickness
Concrete: strength, modulus, thermal coefficient
Edge support: extra width, tied PCC shoulder
Joints: Dowel diameter, spacing
Base course: type, properties, friction w/slab
10
Climate
Traffic
Materials & Construction
Structure,Joints,
Reinforcement
DG Inputs
wAxle load (lb)
DG Outputs
Damage
Distress
DG Process
Mechanistic Response
Time
Damage Accumulation
Field Distress
Damage
Distress Prediction & Reliability
11
Climate
Traffic
AASHTODGDARWin-ME
Inputs
Comprehensive System
DG Outputs
Materials & Construction
Structure,Joints,
Reinforcement
wAxle load (lb)
Damage
Distress
DG Process
Mechanistic Response
Time
Damage Accumulation
Field Distress
Damage
Distress Prediction & Reliability
12
Pavement Characterization
For Each Layer:
„
Physical properties
„
Thermal properties
„
Hydraulic properties
Base
Concrete
Base
Subbase
Subgrade
13
Structural Analysis is Finite Element Based
(ISLAB2000)
14
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, …)
15
Fatigue Damage—Cracking
ƒFinite Element
Model – ISLAB2000
Inputs
Critical Stresses
Incremental Fatigue Damage ∑ = n N
Calibration Fatigue Damage & Field Cracking
Field
Cracking
∑nN
Slab Thickness Vs. Cracking
Slabs cracked %
80
Data: AASHO Road Test
plus I-80 16 years,
12 million trucks
60
40
20
DARWin-ME
0
20 8
cm
9
2510cm
11
3012cm
13
Slab thickness, cm
17
Transverse Joints
„
„
„
Need for dowels.
Benefit of larger
dowels.
Transverse joint
spacing.
18
Need for Dowels & Diameter
Joint faulting, in
0.10
Without dowels
0.08
0.06
25 mm dowel diameter
0.04
32 mm dowel diameter
0.02
0
0
5
10
15
20
25
Heavy trucks (millions)
19
Joint Spacing Effect: MN, MI, CA Projects
Slabs cracked, %
ƒMidwest USA
25
20
Minnesota10 years
15
Michigan15 years
10
5
0
10
15
20
6m
4.6m
Slab length, ft
25
30
Western USA: 21 JPCP 1970’s random joint spacing
z
z
3-4 m joint spacing = 10 percent slabs cracked
5-6 m joint spacing = 34 percent slabs cracked
20
Joint Spacing Effect: CA Project
Percent Slabs Cracked
w100
w80
w60
5.9 m
w40
w20
w0
w0
3.8 m
w5
w10
w15
w20
w25
w30
w35
wPavement Age, years
21
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.
22
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
23
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
24
Impact of Subgrade: JPCP Faulting
Joint Faulting, in
Effect of Subgrade Modulus
0.06
0.05
0.04
0.03
0.02
0.01
0
0
20000
40000
60000
80000 100000 120000
Subgrade Input Mr, psi
25
Impact of Subgrade: JPCP Cracking
Slab Cracking, %
slabs
Effect of Subgrade Modulus
80
60
40
20
0
0
50000
100000
150000
Subgrade Input Mr, psi
26
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
27
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 & Base Thick
Joint spacing
Tied shoulder, widened
Friction slab/base
Monthly Variations of Base Modulus
Elastic modulus, Mpsi
1.6
1.2
0.8
0.4
Months
CTB
ATB
Unbound
l
Ju
O
ct
N
ov
D
ec
Ja
n
Fe
b
M
ar
Ap
r
M
ay
Ju
n
Se
p
Au
g
0
Incremental Damage: Hourly, Monthly, Yearly
“Everything Changes” Over Life
Each axle type &
load application
CTB Modulus
PCC Modulus
Traffic Vol
HMA
Modulus
Granular Base
Modulus
Subgrade
Modulus
0
2
4
6
8
Time, years
30
Climate (temperature, moisture, solar rad., humidity, wind)
„
Integrated Climatic Model (ICM)
z
User identifies local weather stations:
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.
31
Climatic Factors Slab Curling/Warping
Positive temp. gradient
Negative temp. gradient
& shrinkage of surface
Bottom Up Cracking
Top Down Cracking
32
Slab Curling & Warping from Temp. & Moisture
„
„
„
Hourly temperature non-linear gradients
through slab.
Monthly relative humidity changes in top of
slab (changes in drying shrinkage at top of
slab).
Permanent Curl/Warp = Built-in Temperature
gradient + permanent drying shrinkage + creep.
33
Slab Built-In
temperature
gradient during
construction at
time of set
(solar radiation)
34
Curing of Concrete — Effect Cracking
Punchouts per mile
35
30
25
Impact of PCC Construction:
-25 deg F
Day/Night paving, Curing
Severe
-10 deg F
(Typical)
20
-3 deg F
15
Water or
10
Night
5
Cure
0
0
5
10
15
Age, years
20
25
35
Traffic Data Collection Categories
Site Specific
1. AADTT
2. Percent
trucks
3. Growth
Regional
1. Axle load
distributions
2. Direction & lane
distribution factors
3. Monthly
distribution factors
4. Hourly distribution
factors
5. Truck type volume
distributions
State Wide
1. No. axles per
truck type
2. Truck wander
3. Tire pressure &
spacing
4. Axle spacing
5. Wheelbase
spacing
36
50
w 0
12
5
w 00
14
5
w 00
16
5
w 00
18
50
w 0
20
50
w 0
22
50
w 0
24
5
w 00
26
5
w 00
28
50
w 0
30
50
w 0
32
50
w 0
34
5
w 00
36
5
w 00
38
5
w 00
40
5
w 00
42
50
0
w
10
Percent of axles
Different Axle Load Distributions
12
w10
United States
China
w8
w6
w4
w2
w0
Axle load (lb)
Calibration of JPCP
Performance Models
Calibration of Design Models
„
JPCP sections from all over North America
z
z
z
„
Transverse fatigue cracking model
Transverse joint faulting model
IRI smoothness model were calibrated to US
pavement sections.
Results used in Design Reliability to establish
error of prediction
39
LTPP 0214 SPS2, W of Phoenix,
MP 109, 32 Million Trucks
Bottom Up Cracking
(fatigue damage at slab bottom)
wDirection
wof traffic
wOutside Lane
wShoulder
wCritical location
w(bottom of slab)
Top Down Cracking
(fatigue damage at slab top)
wDirection
wof traffic
wOutside Lane
wShoulder
wCritical location
w(top of slab)
Critical top-down stresses
PCC Fatigue Model
⎛ MRi ⎞
⎟
log(N i , j ,k ,l ,m ,n ) = C1 ⋅ ⎜
⎜σ
⎟
⎝ i , j ,k ,l ,m ,n ⎠
wwhere
w Ni,j,k,…
w
w Mri =
w σi,j,k, . =
w C1 =
w C2 =
C2
= allowable number of load
applications
PCC modulus of rupture
applied stress
calibration constant, 2.0 Field
calibration constant, 1.22 Field
N, Number of Stress Repetitions to First Fatigue Crack
w1E+07
* wCORPS
wAASHO
wExtended AASHO
w1E+06
w1E+05
* *
* * * *
** * * *
* ** *
* ** * * *
* ** * * * *
** *
*
*
* * *** * * *
*
*
*
*
*
*
**
*
w1E+04
N
w1E+03
w1E+02
w1E+01
w0
0.2
0.4
0.6 0.8
1
1.2 1.4
wStress Ratio, (σ/MR)
1.6
1.8 2.0
Miner’s Fatigue Damage Model
DI F = ∑
wWhere
w
DIF =
w
n i,j,k,=
w
Ni,j,k,. =
n i , j , k ,l , m , n , o
N i , j , k ,l , m , n , o
fatigue damage, accumulative
number of applied load applications
number of load applications to crack
Transverse Cracking Fatigue Damage Model
DI F = ∑
wWhere
w
DIF =
w
n i,j,k,=
w
w
Ni,j,k,. =
w
n i , j , k ,l , m , n , o
N i , j , k ,l , m , n , o
Miner’s Damage
Fatigue damage (TD or BU)
Applied load applications at
condition i, j, k, l, m, n
Allowable number of load
applications at condition i, j, k, l, m, n
wi = Age (months/years life)
wk = Axle type
wm = Equivalent Temp gradient
j = Month/day or night/hour
l = Axle load level
n = Lateral truck path
Concrete Sections Calibration (JPCP, OLs, CPR)
48
Correlation of Damage to Field Cracking
Percent slabs cracked
100
80
60
w N = 520 observations
w R2 = 84 percent
wSEE = 5.72 percent
40
20
0
1.E-08
1.E-06
1.E-04
1.E-02
Fatigue Damage
1.E+00
1.E+02
JPCP Cracking Model Coefficients
CRK =
1
C
5
1 + C 4(DI F )
C4 & C5 were determined through statistical regression using
hundreds of field JPCP projects across North America
Fatigue Cracking in Field Correlation to Damage
Percent slabs cracked
100
80
CRK =
60
1
1 + C 4(DI F )C 5
40
20
0
1.E-08
1.E-06
1.E-04
1.E-02
Fatigue Damage
1.E+00
1.E+02
Example of Measured & Predicted Slab Cracking
wLTPP 0217, LCB
Example of Measured & Predicted Slab Cracking
wLTPP 0214, Agg Base
Design Reliability DARWin-ME
„
„
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.
54
DARWin-ME Design Reliability
„
JPCP
z RF = P [Fault < Critical Fault]
z RC = P [Crack < Critical Crack]
z RIRI = P [IRI
< Critical IRI]
Design Reliability Example JPCP
„
Example: Project 1993-2013 = 20 years (32
million trucks in outer lane)
z
z
z
z
z
Design Reliability: 50, to 99.9 %
Standard deviation: Error of prediction
Transverse fatigue slab cracking: 10% slabs
Transverse joint faulting: 0.12 inch
IRI: Initial = 60 in/mile, Terminal = 150 in/mile
AZ JPCP Design Reliability Effect
Slab Thickness, in.
13
12
wNo fatigue cracking
11
10
9
8
wLots of fatigue cracking
7
50%
61%
97.4
Design Reliability, %
99.8
Recommended Design Reliability Criteria: Arizona
Divided Non Divided, Performance Highways, 2001 –
Non Interstate, Criteria
Freeways, 10,000 ADT
10,000+ ADT
Interstates
Design Reliability
97% 95%
90%
501‐2,000 ADT
< 500 ADT
80
75
Design Performance Criteria
„
„
What level of Distress & IRI should we design
and at what level of Reliability?
In general:
z
z
Strive for the “Goldilocks” level: not too high, not too low
for an optimum solution!
Traffic level, potential congestion from lane closure, and
access to detours are clearly major factors.
Effect Slab Cracking Criteria
Design Slab Thickness, in
13
12
11
10
9
8
7
0
5
10
15
20
25
Percent Slabs Cracked Performance Criteria
30
Recommended Performance Criteria
JPCP & Composite Pavement for Arizona
Divided Non Divided, Performance Highways, Non Criteria
Freeways, Interstate, Interstates 10,000+ ADT
2001 –
10,000 ADT
501‐2,000 ADT
< 500 ADT
Cracking, % Slabs
10
10
15
15
20
Faulting, mm
3
3
3
4
5
IRI, m/km
2.38
2.38
2.54
2.54
2.86
GENERAL
INFO
PERFORMANCE
EXPLORER
WINDOW
LAYER
PROPERTIES
PAVEMENT
STRUCTURE
ERROR
LIST
RUN
PROGRESS
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
63
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
64
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/km
65
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.
66
WS JPCP Design Comparison
14 years, 5.5 million trucks
Distress
Slab
cracking
Measured
Existing Design
4-m = 0%
6-m = 38%
Joint faulting
1.75-mm
IRI
Predicted
New Design
4.6 m = 0 %
0.25-mmn
(37-mm dowels)
1.1 m/km
2.3 m/km
DARWin-ME 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, $
68
Example: CA Life Cycle Analysis
„
„
„
Analyses conducted during investigation of long
life concrete pavements.
Conducted by Prof. John Harvey of UC Davis &
team.
Comparison of 20, 40 and 100 years for JPCP
Traffic Closures
„
Minimal maintenance and rehabilitation would greatly
reduce lane closures for work zones and maintenance
causing reduced congestion & user costs, and reduced
fatalities over the 100 years.
Design Parameters: Route 210 CA
LCCA Results for Route 210 CA
(no User Costs calculated)
Optimum Design Life
„
„
When traffic will be heavy over much of
the design life, design for as long a
time period as possible for a given
location.
Limitations include:
z
z
z
z
Materials durability
Harsh climate (chain wear, materials)
Subgrade movement (heave, swell, settle)
Desired design reliability
Design Life for HMA & PCC was 20 years
Utah Survival Curves – I-15 (100+ miles)
Percent Sections Survived
100
90
80
HMA
70
PCC
60
50
40
30
20
10
0
0
5
10
15
20
Age, years
25
30
35
40
Improved Pavement Longevity
Accumulated Percent
100
Current
Performance
Increased life
Performance
with improved
technology
50
Design
Construction
Materials
Maintenance
0
Life of Pavement