JOINT LOAD TRANSFER EFFICIENCY OF RIGID PAVEMENT CONSIDERING DYNAMIC EFFECTS UNDER A SINGLE MOVING L...
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JOINT LOAD TRANSFER EFFICIENCY OF RIGID PAVEMENT CONSIDERING DYNAMIC EFFECTS UNDER A SINGLE MOVING LOAD. Xinhua YU, Yumin ZHOU, Zhiming TAN Tongji University, PRC Edward H Guo SRA International, USA. FAA 2010, Atlantic, New Jersey, April 20-22, 2010. OUTLINE.

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JOINT LOAD TRANSFER EFFICIENCY OF RIGID PAVEMENT CONSIDERING DYNAMIC EFFECTS UNDER A SINGLE MOVING LOAD

Xinhua YU, Yumin ZHOU, Zhiming TAN

Tongji University, PRC

Edward H Guo

SRA International, USA

FAA 2010, Atlantic, New Jersey, April 20-22, 2010


Outline
OUTLINE DYNAMIC EFFECTS UNDER A SINGLE MOVING LOAD

  • Observation from Field and Tests

  • Conceptual Analysis of the Dynamic Modeling

  • Findings


Does low ltes cause early slab cracks i

Winter DYNAMIC EFFECTS UNDER A SINGLE MOVING LOAD

Ioannides and Korovesis, 1990, 1992

Does Low LTEs Cause Early Slab Cracks? (I)


Does low ltes cause early slab cracks ii

5 DYNAMIC EFFECTS UNDER A SINGLE MOVING LOAD

Does Low LTEs Cause Early Slab Cracks? (II)



Differences Between Models (I) Cracks?

How to define Load Transfer Efficiency? (LTE)

FHWA

FAA

Above two are equivalent only for static modeling

LTE is a pending problem in dynamic modeling


Differences between models ii
Differences Between Models Cracks? (II)

  • Fundamental differences exist between the model and field reality

  • The model is static

    • the speed of wheel is assumed to be zero

    • the position of load is fixed on one side of the joint

  • The reality is dynamic

    • The wheels move with different speeds

    • The position of the wheel changes at any moment


Differences between models iii
Differences Between Models Cracks? (III)

Reality – Strain history when a four wheel gear across a joint

LTE(S) is temporarily defined by


Differences between models iv
Differences Between Models Cracks? (IV)

Evaluation Using HWD (FWD) Machine

LTE(S) calculated from the measured LTE(W)


Differences between models v
Differences Between Models Cracks? (V)

Static Modeling in Existing Analysis

Ioannides and Korovesis, 1990, 1992


What is new in this paper? Cracks?

  • Dynamic model is used to replace the static model;

  • The sensitivity of four parameters have been considered in analysis: Load speed, pavement damping, foundation reaction modulus and foundation damping



A Cracks?

LTE=

B

Conceptual Analysis (I)

Static Model

Dynamic Model

Makes the peak load be shared by the unloaded slab. The higher the speed, the more will be shared.

Makes the peak response decrease and delay in occurrence


Conceptual Analysis (II) Cracks?

  • Static model is a special case of dynamic model after two major conditions are satisfied:

  • Damping = 0;

  • Load moving speed is zero;

  • Therefore, reliability of the dynamic analysis can be verified by existing static analysis.


Findings i parameters
Findings I Cracks? - Parameters

pavement damping

Cs=0.008~1.2MN·s/m3

foundation reaction modulus

k=40~90 MN/m3

foundation damping

Ck=0.002~0.2 MN·s/m3


Findings ii strains and deflections at specified points i e 1 e 2
Findings II Cracks? - Strains and Deflections at Specified Points i , e1 ,e2

(1- Cs =0.008MN·s/m3, 2- Cs =0.4MN·s/m3, 3- Cs =1.2MN·s/m3)

Higher damping, lower responses, higher speed, lower responses


Findings iii time lag of peak strain at point e 1
Findings III Cracks? - Time lag of peak strain at point e1

ΔX (=Δt∙v)

(1- Cs =0.008MN·s/m3, 2- Cs =0.4MN·s/m3, 3- Cs =1.2MN·s/m3)

The higher pavement damping, the more delay the calculated peak responses


Findings IV Cracks? - Measured LTE(S) at FAA’s NAPTF


Findings v lte s versus moving speed v
Findings V Cracks? - LTE(S) versus Moving Speed v

(kw=3000 MN/m3)

(kw= 0)

(1- Cs =0.008MN·s/m3, 2- Cs =0.4MN·s/m3, 3- Cs =1.2MN·s/m3)

LTE(S) seems no longer equal to 0 while speed v great than 0 and the joint shearing stiffness kw=0.


Findings vi lte s versus lte w dynamic model
Findings VI Cracks? -LTE(S) versus LTE(w)–Dynamic Model

(1- Cs =0.008MN·s/m3, 2- Cs =0.4MN·s/m3, 3- Cs =1.2MN·s/m3)


Findings vii effects of foundation modulus k c s 0 v 5m s
Findings VII – Cracks? Effects of Foundation modulus k (Cs=0, v=5m/s)

The influence of foundation reaction modulus k on LTE(S) is not significant


Findings viii effects of foundation damping c k c s 0 v 5m s
Findings VIII – Cracks? Effects of Foundation damping Ck (Cs=0, v=5m/s)

The influence of foundation damping Ck

on LTE(S) is quite small


Conclusions
CONCLUSIONS Cracks?

  • The static model under-estimates the load transfer efficiency and over-estimates the risk for bottom-up cracks at concrete pavement joints;

  • With increase of the load moving speed v, the joint load transfer efficiency LTE(S) increases;

  • With increase of the pavement damping Cs, the joint load transfer efficiency LTE(S) increases;

  • The ratio c (LTE(S) dynamic against LTE(S) static)varies in the range 1.0 to 2.0 mainly depending onvariables v and Cs;

  • The joint load transfer efficiency is insensitive to the reaction modulus k and damping Ckof concrete pavement foundation.


Thank you
THANK YOU! Cracks?


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