CRCP MECHANISTIC- EMPIRICAL PAVEMENT DESIGN Hua Chen, P.E Andy Naranjo, P.E Rigid Pavements and Concrete Materials Branch Construction Division, TxDOT 2015 Short Course

Table of Contents

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7-9

10-16

17-32

33-38

3-6 Background

Current Empirical Concrete Pavement Design

Development of Mechanistic-Empirical CRCP Design

TxCRCP-ME Design Program

TxCRCP-ME vs. AASHTO 1993 Design

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2

3

4

5

39-40 Summary 6

Background

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Longitudinal Joint

Longitudinal Steel

Transverse Steel Tie Bars

4” ACP Base

CRCP after Concrete Paving

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Statewide 13,969 lane miles of CRCP

5

146

1,726

311 466 542

4 7 23 196

68 46

6,002

54

490

76 69

2,170

138 313

7 33 15

931

135

-

1,000

2,000

3,000

4,000

5,000

6,000

PAR FTW WFS AMA LBB ODA SJT ABL WAC TYL LFK HOU YKM AUS SAT BRY DAL ATL BMT PHR LRD BWD ELP CHS

Lane

Mile

s

Districts

CRCP Lane Miles - 2015 PMIS

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Statewide 3,681 lane miles of CPCD

122 41 73

3 1 8 1 86

35 20

482

5 4 28

1,890

95

713

3 14 57

-

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

PAR FTW WFS AMA LBB ODA SJT WAC TYL LFK HOU YKM SAT BRY DAL ATL BMT PHR LRD CHS

Lane

Mile

s

Districts

CPCD Lane Miles - 2015 PMIS

Current Empirical Concrete Pavement Design

AASHTO 93 Design Method – Based on empirical data for AASHTO Road Test built in Illinois during the

late 50’s – Consisted of 7 miles of two-lane pavements in the form of six loops and a

tangent, half concrete, half asphalt – Most of the concrete sections were JCP not CRCP

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8

Δ Serviceability Index

Load Transfer Coefficient

Design ESALs

Reliability

Standard Deviation

Modulus of Rupture Drainage Coefficient

Modulus of Elasticity

Subgrade Reaction

Pavement Thickness

Terminal Serviceability Index

Darwin 3.1

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Development of Mechanistic-Empirical CRCP Design

TxDOT has used the AASHTO 93 Guide for the design of CRCP, and it has served TxDOT well for the design of CRCP despite its limitations. In March 2004, NCHRP 1-37 report and the mechanistic-

empirical pavement design guide software (MEPDG) were released. In 2005, TxDOT initiated Research 0-4714 to evaluate the

MEPDG for potential implementation. The study recommended, for various reasons, not to implement the MEPDG as a replacement for the design methods currently being used.

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Development of Mechanistic-Empirical CRCP Design

In 2007, TxDOT initiated Research 0-5832, to develop a mechanistic-empirical CRCP design procedures that would model the performance of TxDOT’s typical concrete pavement structure and performance. Three-dimensional analysis was conducted for in-depth analysis

of mechanistic behavior of CRCP, including the interactions between longitudinal steel and concrete.

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Development of Mechanistic-Empirical CRCP Design

Over the past decade, there has been a push to make pavement design less of an art and more of a science

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• Modulus of Rupture

• Elastic Modulus

• K-Value of Subgrade

• Serviceability Index

• Load Transfer Coeff.

• Drainage Coeff.

• Standard Deviation

• Reliability

• Traffic

Empirical Design Inputs

Pavement Thickness

• Modulus of Rupture

• Elastic Modulus

• K-Value of Subgrade

• Drying Shrinkage

• CoTE of Concrete

• Setting Temperature

• Construction Info

• Traffic

• Pavement Thickness

• Performance Criteria

Mechanistic Design Inputs

Performance Prediction

Development of Mechanistic-Empirical CRCP Design

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Input Critical

Concrete Stress

Transfer function 1. Concrete strength 2. Fatigue life 3. Loading applications

Damage Distress

1. Cumulative damage 2. Distress

Critical Stresses

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Pavement Distress Types

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Large Surface Defects46.6%

Real Punchouts14.2%

Repair Joints 20.7%

Construction Joints18.5%

Pavement Distresses

Distress Issues Large Surface Defects are primary a result of high CTE aggregates. No longer an issue! 40% of the distresses in concrete pavements occur at joints. 40% of the punch-outs were located at transverse joints.

Punch-Outs are Primary Structural

Distress Type on CRCP

Pavements

Transfer Function

TXCRCP-ME Transfer Function

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𝑃𝑃 = 18.985

1 + 5𝐷1.1

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TxCRCP-ME Design Program

Program Structure

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Instructions

Spreadsheet Tabs

“Tabs”

Inputs Temperature Soil Classification K-Table Composite K S-Table Stress Analysis Result Final Result Time vs. Punchout

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TXCRCP-ME Inputs

Project Identification Design Parameters Design Traffic Concrete Layer Information Support Layer Information

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Several of the TxCRCP-ME inputs are hard coded into the spreadsheet. These inputs include: • drying shrinkage • setting temperature • month of construction • COTE value It was decided that these inputs will not be known at the time of designing the pavement and therefore typical or specification values of for each input were set and not allowed to be changed in the spreadsheet.

Design Parameters

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TxDOT design life for CRCP is 30 yrs

10 punchouts/mile is recommended. Lower values maybe warranted for interstate highways

Design Traffic

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Input the total # of lanes in one direction.

Input Design Traffic in one Direction. Program will internally calculate the reduced design traffic.

Concrete Layer Information

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Input trial slab thickness

570 psi is new flexural strength requirement.

Support Layer Information

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Select AASHTO or USCS System of Soil Classification.

Composite K value will be calculated based on inputted values above.

Select Base Type, and Input Base Thickness and Modulus

Select Soil Classification of subgrade from dropdown list

Temperature

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Average Weather Data for Each District

Composite K

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Stress

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Concrete Stresses

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Concrete Stress Due to Traffic

Concrete Stress Due to Environmental Loading

Concrete Stress of Combined Traffic and Environmental Loading

Analysis Result

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Final Result

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Predicted # of Punchouts

Time vs. Punchout

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0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 100 200 300 400

Num

ber o

f Pun

chou

ts p

er M

ile

Time [months]

Time vs. Number of Punchouts

TxCRCP-ME vs. AASHTO 1993 Design

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An analysis of pavement design thickness was completed for six districts that commonly construct concrete pavement (HOU, ALT, DAL, FTW, ELP, WAC).

The pavement design thickness was determined for 26

traffic levels (1 million to 200 millions) and composite K-values of 300 pci, 500 pci, 800 pci, and 1,000 pci. Total 624 design thicknesses for each design procedure.

TxCRCP-ME vs. AASHTO 1993 Design

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AASHTO '93 Design Inputs TxCRCP-ME Design Inputs

Input Value Input Value

30 yr Traffic Varies 30 yr Traffic Varies

K-value Varies K-value Varies

Modulus of Rupture 620 psi Modulus of Rupture 570 psi

Modulus of Elasticity 5,000, ksi Modulus of Base Varies to set K-value

Serviceability Index 2.5 Base Thickness 6 inches

Load Transfer Coeff. 2.6 Subgrade Class Varies to set K-value

Drainage Coeff. Varies with District Punch-outs per mile 10

Standard Deviation 0.39

Reliability 95%

Atlanta District CRCP Thickness Comparison

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5

6

7

8

9

10

11

12

13

14

15

161 3 5 10 20 30 40 50 60 70 80 90 100

150

200 1 3 5 10 20 30 40 50 60 70 80 90 100

150

200 1 3 5 10 20 30 40 50 60 70 80 90 100

150

200 1 3 5 10 20 30 40 50 60 70 80 90 100

150

200

Des

ign

Slab

Thi

ckne

ss (i

nch)

ESAL (million)

AASHTO 93TxCRCP-ME

Composite K300 psi/in

Composite K500 psi/in

Composite K800 psi/in

Composite K1000 psi/in

Houston District CRCP Thickness Comparison

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5

6

7

8

9

10

11

12

13

14

15

161 3 5 10 20 30 40 50 60 70 80 90 100

150

200 1 3 5 10 20 30 40 50 60 70 80 90 100

150

200 1 3 5 10 20 30 40 50 60 70 80 90 100

150

200 1 3 5 10 20 30 40 50 60 70 80 90 100

150

200

Des

ign

Slab

Thi

ckne

ss (i

nch)

ESAL (million)

AASHTO 93TxCRCP-ME

Composite K300 psi/in

Composite K500 psi/in

Composite K800 psi/in

Composite K1000 psi/in

TxCRCP-ME vs. AASHTO 1993 Design

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TxCRCP-ME method is slightly more sensitive to support conditions as indicated by the thinner pavements at higher composite K-values. K-value of 300 psi/in, the TxCRCP-ME resulted

the same or slightly thicker pavement K-value of 500 psi/in, the TxCRCP-ME resulted

slightly thinner pavement

TxCRCP-ME vs. AASHTO 1993 Design

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K-value of 800 psi/in and at low traffic volumes, the TxCRCP-ME resulted up to 1” thinner pavement. At higher traffic volumes, the pavement thickness was similar between the two methods.

K-value of 1000 psi/in and at low traffic volumes, the TxCRCP-ME method resulted in pavements that were up to 1.5” thinner pavement. At higher traffic volumes, the pavement thickness was up to 1/2” thinner compared to AASHTO ‘93.

Summary

TxCRCP-ME program is a simple MS Excel spreadsheet to perform the design. The TxCRCP-ME spreadsheet has been thoroughly testing and

compared to the current design method. The implementation includes

– Revise Pavement Design Guide – Obtain FHWA approval – Conduct Statewide trainings

For CPCD pavement design, use Darwin3.1, AASHTO 1993 Method till the TXCPCD-ME program developed.

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Rigid Pavement and Concrete Materials Branch Construction Division, TxDOT

Andy Naranjo, P.E. Branch Manager (512) 506-5858 Hua Chen, P.E. (512) 506-5846

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