Many concrete bridge decks develop transverse cracks soon after construction. The aims of this project were to investigate the causes of such cracking and to specify methods to reduce its incidence. Literature, research reports, and current practices concerning transverse cracking in bridge decks were reviewed to learn the extent of and the perceived causes of cracking. All departments of transportation in the United States and many foreign transportation departments were surveyed to learn the extent of deck cracking, and standard design and construction practices. The survey response revealed that transverse bridge deck cracking is a severe problem, since about half the bridges in the United States develop early cracking. Construction methods vary widely, as do techniques used in attempts to prevent cracking. The Portland-Columbia Bridge was instrumented and monitored during its redecking. The comprehensive recorded data provide important insight into early bridge behaviour and cracking, influenced by thermal loading and concrete shrinkage. Systems of equations to predict shrinkage and thermal stresses in a composite bridge were developed. behaviour predicted by these equations compared favourably with actual measured behaviour of the Portland-Columbia Bridge. The equations allow bridge designers to predict thermal and shrinkage stresses that may develop in their designs. Designers can evaluate and compare the thermal and shrinkage stresses of various designs. Analytical studies using the derived equations evaluated the influence of various material and geometry factors on deck stresses and cracking. The analyses examined the effects of various concrete properties, including modulus of elasticity, creep, drying shrinkage, and coefficient of thermal expansion. Girders were either steel or concrete, small or large. Simply-supported and continuous spans were analysed. The effects of deck reinforcement were also studied. Three different temperature conditions and two different deck drying shrinkage profile conditions were analysed. About 18,000 combinations of system and conditions were analysed. The analytical study determined the material properties and geometries most likely to cause transverse deck cracking. These are deck restraint, the concrete modulus of elasticity and creep, and shrinkage and thermal strains. Because decks are restrained primarily by their supporting girders, and span length limits girder stiffness, often little can be done to reduce restraint. However, concrete properties have a large effect on stresses, and concrete properties can be easily changed. Construction techniques can also be easily improved to reduce early thermal strains and shrinkage. A test method to predict cracking tendency of concrete mixes was developed. This project identified and ranked the factors or combinations of factors that contribute to transverse cracking of newly constructed bridge decks. (A0
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