Damage Factor Assessment through Measuring Direct Response of - - PowerPoint PPT Presentation

Damage Factor Assessment through Measuring Direct Response of Asphalt Pavement due to Heavy Loading

A’arif Hamad-MSc. Candidate

• Dr. Lynne Cowe Falls- Supervisor

CONTENTS

Introduction Background Objective of Study Methodology Preliminary Results Conclusions and Suggestions for Future Work

INTRODUCTION

Low Volume Roads Under Heavy Loading

• 1. Low traffic volume
• 2. Structurally under-designed roads

Road Authorities and Restrictions on Roads

• 1. Seasonal ban (thaw season)
• 2. Maximum allowable axle loading

Load Equivalency Factors (LEFs)

• 1. AASHTO test road
• 2. Common vehicle configuration

TAC Recom. Max. Axle Wt.

52.9 24.00 50.7 23.00 46.3 21.00 Tridem 37.5 17.00 Tandem 20.1 9.10 Single 12.1 5.50 Steering Kips Tonnes

Heavy Vehicle Under Study

Differences From Traditional Loading

• Four Adjacent Axles
• Axle Loads Exceed the Recommended Limits
• Super Single Tires
• Hydraulic Suspension System

43,950 (96.8) 9,200 (20.3) 10,650 (23.4) 12,400 (27.3) 11,700 (25.8) Total- kg (Kips) Axle 4- kg (Kips) Axle 3- kg (Kips) Axle 2- kg (Kips) Axle 1- kg (Kips)

Motivation For This Study

• Winter Season
• Average Two Moves in a Month
• Moving Crane on Four Axles Without Using Extra Dollies
• Money Saved ?

BACKGROUND

• 1. Christison et al.1978

Various axle configurations (single on dual tires, single on single tires, tandem on dual tires, and single on single tires for self- propelled earthmovers. Wide range of axle loads for each axle type. Instrumented two Alberta standard full depth asphalt concrete pavements (200 & 280 mm).

BACKGROUND

The study results related the interfacial strains and surface deflections to several factors (pavement age, pavement temperature, and vehicle velocity). Calculated LEFs based on different concepts (surface deflection, flexural distress. Also proved agreement of calculated LEFs with the pavement performance according to AASHTO test road.

BACKGROUND

• 2. Christison 1990

Investigated two cranes with heavy axle loads (total wt.590 & 627 kN respectively). Instrumented two asphalt concrete roads in Alberta each with 135 mm ACP layer on two different base layers. LEF’s values ranging from 5.2 to 26.8 were found in the study for the cranes. LEFs were related to pavement structure, Crane type, traveling speed,and concept for LEFs calculation.

OBJECTIVE OF STUDY

Study the Effect of Heavy Loading on Thin Membrane Flexible Pavement Update Historical Data (LEFs, Dynamic loading, Seasonal factors) Develop New Performance Models Evaluate New Technologies and Equipment (Super singles, CTI) Update/Validate Existing Road User Regulations

METHODOLOGY

• A. Field Test

i. Construction and instrumentation of a test road ii. Conducting a series of tests using the heavy loads and standard load

• iii. Analyzing data and find results
• B. Finite Element Analysis
• C. Comparison Between Field Results and

Analytical Results

• D. Final Conclusion

Test Road

• Three Successive Sections
• Same Dimensions – (150 m x 9.0 m )
• Different Pavement Structure
• 1. Granular Base Course (GBC) section
• 2. Cold Mix Asphalt (CMA) section
• 3. Hot Mix Asphalt (HMA) section
• Instrumentation is Similar for the CMA & HMA
• Sections. Adjustment made for the GBC

Section

PLAN VIEW Centre line Strain Transducer Moisture Gauge 1000mm 1000mm 390mm Temperature Profile D.A.S CROSS-SECTION VIEW Hot Mix Asphalt 110 mm Granular Base Course 300 mm Subgrade Prep 150 mm Centre lane 1000mm 1000mm 390mm Pressure Gauge 150 mm Cold Mix Asphalt 50 mm GBC – 50 mm GBC – 50 mm

N.T.S.

Test Road Instrumentation

Testing Sequence/1

• Crane 10 km/hr

Standard 18 kip

• Crane 5 km/hr

Standard 18 kip

• Crane Creep
• Creep Standard 18 kip
• Standard 8 wheel Tandem(17000kg) @60 km/hr
• Standard 18 kip @60km/hr

5 4 3 2 1 Repetition number

Load

Testing Sequence/2

• Crane 30 km/hr

Standard 18 kip

• Crane 20 km/hr

Standard 18 kip

• Crane 15 km/hr

Standard 18 kip

• Crane 10 km/hr

Standard 18 kip 5 4 3 2 1 Repetition number

Load

Testing Sequence/3

• Crane 60 km/hr 7 axle configuration-CR02
• Standard 18 kip @60km/hr

Standard 18 kip

• Crane 60 km/hr 4 axle configuration-CR01

Standard 18 kip

• Crane 50 km/hr

Standard 18 kip

• Crane 40 km/hr

Standard 18 kip 5 4 3 2 1

PRELIMINARY RESULTS

Preliminary results discuss the following:

• 1. Interfacial Strain (Between the Asphalt

Concrete & the Granular Base Course Layers)

a) Along travel direction (Longitudinal) b) Perpendicular to travel direction (Transversal)

• 2. Vertical Stress in the Sub-grade

• Long. Interfacial Strain

CR02 0.0002

• 0.0004
• 0.0002

0.0004 0.0006 0.0008 0.001 0.0012 0.2 0.4 0.6 0.8 1 1.2 1.4 ST18 CR01

Strain mm/mm Time (Seconds)

Longitudinal Strain-HMA section, Speed 60 km/hr

• Max. Long. Interfacial Tensile Strains

1766 (2226) 1731 (2122) 1783 (2278) 1951 (2347) 1844 (2343) 1832 (2273) 1732 (2261) 1057 (1704)

CMA

819 (1054) 844 (1112) 865 (1123) 914 (1157) 932 (1177) 938 (1170) 923 (1164) 334 (379)

HMA Speiring Crane – Seven Axles Configuration (CR02)

• 1792

(2309) 1677 (2110) 1806 (2382) 1703 (2238) 1057 (1704)

CMA

• 1049

(1392) 1031 (1361) 1051 (1345) 1053 (1362) 334 (379)

HMA Speiring Crane – Four Axles Configuration (CR01) 7

(x10-6)

6

(x10-6)

5

(x10-6)

4

(x10-6)

3

(x10-6)

2

(x10-6)

1

(x10-6)

Axle # for the Tested Vehicle Standard 18 Kips Truck (ST18) (x10-6) Test Road Section Tested Vehicle

• Long. Strain Comparison/1

ST18 CR01 CR02 CR01 ST18 CR02 313% 267% 165% 170%

HMA Section CMA Section

CR01 CR02

10 - 20%

HMA & CMA Sections (I) (II) (III)

• Long. Strain Comparisons/2

Maximum Tensile Strain Under Wheel Path / Both Cranes

HMA Section CMA Section

+65%

• 65%
• 85%

CMA Section HMA Section

for Both Cranes

(IV) (V)

Transversal Strain Results/1

• For both HMA & CMA

Sections , Tensile Strains were Generated Under the Wheel Paths

• 1. For CR01

εt = (75-80)% εl

• 2. For CR02

εt = (55-75)% εl

εl εt

Travel Direction

Transversal Strain Results/2

• For CR01, Strain under

OWP is 35-50% higher than under IWP

• For CR02, Strain Under

OWP is 15-30% higher than Under IWP Travel Direction

OWP IWP Center Line

• Trans. Strain Distribution

T T T C C C

I3 O1 O2 O3 I1 I2 I1

C T/C T T C T/C

ST18 CR01 & CR02

O1 O3 O2 I2 I1 I3

Travel Direction

• V. Stress in Sub-grade

Vertical Pressure in the Sub-grade for Different Vehicles- HMA Section, V=60km/hr

5 10 15 20 25 0.5 1 1.5 2 Time (Seconds) Vertical Pressure (kPa) ST18 CR01 CR02

• V. Stress on top of Subgrade

ST18 CR01 CR02

90-155%

HMA Section (I) (II)

35-110%

CR02

HMA Section

CR01

40-55%

CONCLUSIONS & FUTURE WORK

• No Clear or Final Conclusions Could be

Presented Due to Limited Time Available for Full Analysis.

May 25 to June 24 2005 30 days Test road Construction and Instrumentation June 25-26, 2005

2 days

Preparation for and Doing the Field Test June 27 – July 15

18 days

Looking at all the data and presenting preliminary results in this paper

Suggestions for Future Work

• For Future Work.

1.Study the edge effect on the pavement response, making use of the strain gauges array design. 2.Include the tire characteristics to the variables in the testing program such as tire size, tire type, tire pressure …etc. 3.Investigate the effect of any future work to the test road by comparing current results with the new ones.