Diseño de Pavimentos de Hormigón para alcanzar larga Vida útil
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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 Finite 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, % Midwest 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
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