Investigation of Likelihood of Cracking in Reinforced Concrete Bridge Decks

Adel Elsafty,Ahmed Abdel-Mohti

doi:10.1007/s40069-013-0034-3

Abstract

One of the biggest problems affecting bridges is the transverse cracking and deterioration of concrete bridge decks. The causes of early age cracking are primarily attributed to plastic shrinkage, temperature effects, autogenous shrinkage, and drying shrinkage. The cracks can be influenced by material characteristics, casting sequence, formwork, climate conditions, geometry, and time dependent factors. The cracking of bridge decks not only creates unsightly aesthetic condition but also greatly reduces durability. It leads to a loss of functionality, loss of stiffness, and ultimately loss of structural safety. This investigation consists of field, laboratory, and analytical phases. The experimental and field testing investigate the early age transverse cracking of bridge decks and evaluate the use of sealant materials. The research identifies suitable materials, for crack sealing, with an ability to span cracks of various widths and to achieve performance criteria such as penetration depth, bond strength, and elongation. This paper also analytically examines the effect of a wide range of parameters on the development of cracking such as the number of spans, the span length, girder spacing, deck thickness, concrete compressive strength, dead load, hydration, temperature, shrinkage, and creep. The importance of each parameter is identified and then evaluated. Also, the AASHTO Standard Specification limits live-load deflections to L/800 for ordinary bridges and L/1000 for bridges in urban areas that are subject to pedestrian use. The deflection is found to be an important parameter to affect cracking. A set of recommendations to limit the transverse deck cracks in bridge decks is also presented.

Highlights

Cracking can occur in hardened mature concrete, transverse deck cracking are more likely to occur in bridge decks in early ages
In order to produce the maximum moment and in turn a higher potential of cracking, the first and third span of the bridge was loaded with truck load (TR) while the middle span was free of TR (Fig. 11)
This designed scenario was selected to ensure that the case, at which maximum tensile stress to develop in the deck, is considered

Summary

Introduction

Cracking can occur in hardened mature concrete, transverse deck cracking are more likely to occur in bridge decks in early ages. The concrete would not crack if this shrinkage could occur without the restraint from structural elements, the subgrade, or the moist interior of the concrete itself This volume change coupled with restraint cause tensile stresses in the concrete that can lead to cracking. The dissipation of the heat of hydration of cement and changes in ambient temperature can create temperature differentials that cause tensile stresses in concrete structures These tensile stresses are proportional to the temperature differential, the coefficient of thermal expansion, the effective modulus of elasticity, and the degree of restraint. Methods of reducing thermal cracking include reducing maximum internal core temperature, delaying the onset of surface cooling, controlling the rate at which the concrete cools, and increasing the early age tensile strength of the concrete (PCA 1970)

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Results

Conclusion