Transverse Cracking in Concrete Bridge Decks

This study sought to determine the dominant parameters that lead to premature transverse cracking in bridge decks and to make recommendations that help reduce cracking tendency in bridge decks. The project includes two main parts: a field study and a parametric study. The field study identified 72 bridges in the Minneapolis/St. Paul area and explored the correlation between the observed cracking of those bridges and available design, material, and construction-related data. The parametric study investigated the relative influence of the factors that affect transverse deck cracking through a controlled nonlinear analysis study. Variables included: shrinkage, end restraint, girder stiffness, supplemental steel bar cutoff, cross frames, splices, deck concrete modulus of elasticity, and temperature history. In addition, four bridges from the companion field study were modeled to compare the analytical results with the actual crack patterns. Based on these results and correlation with other research, the study identified the following dominant factors affecting transfer cracking: shrinkage, longitudinal restraint, deck thickness, top transverse bar size, cement content, aggregate type and quantity, air content, and ambient air temperature at deck placement. Recommended practical improvements to bridge deck construction, in order of importance, include: using additives to reduce shrinkage of the deck concrete, using better curing practices, and minimizing continuity over interior spans.