Use of Longitudinal Expansion Joints in Wide-Bridge Applications to Reduce Deck Cracking

It is a very common practice to use longitudinal expansion joints to create dual-direction bridges in applications that would have otherwise resulted in bridges that are very wide. Unfortunately, the introduced longitudinal expansion joint can result in deterioration similar to that resulting from using transverse joints at bridge abutments and piers. The reason that longitudinal expansion joints are used in wide bridges is related to concerns about deck cracking resulting from constrained expansion and contraction. The main objective of this research was to evaluate the need for longitudinal expansion joints by assessing the relationship between bridge width (and other factors) and the propensity for deck cracking. To achieve this objective, an integral abutment bridge was selected to conduct live-load and thermal-load testing to provide field testing data for the calibration of a three-dimensional (3D) finite-element model (FEM) that would be used for a comprehensive parametric study. A combination of live load plus temperature and shrinkage loading was applied to validate the model. During the parametric study, three different width integral abutment bridge models were built to evaluate the need for the longitudinal expansion joint. Additionally, models with 45 degrees skew and without an integral abutment were developed to study the relationship between bridge skew, abutment type, and the development of longitudinal and diagonal cracks. A review of historical deck-crack maps from actual bridge inspection reports was conducted for 40 common bridges. The results of this review of historical deck-crack development compared favorably with the parametric study results. The results of this study indicate that the use of a longitudinal deck joint will not reduce deck-end cracks. It was further found that the commonly observed longitudinal and diagonal cracking in the deck near the abutment on integral abutment bridges is a result of the restraint induced by the integral abutment combined with temperature and shrinkage differences between the abutment and the deck, and will occur for bridges of any width and any skew. It was also found that bridges that use conventional abutments (sometimes referred to as stub abutments) are not prone to develop this type of cracking, even for very wide bridges. (C) 2016 American Society of Civil Engineers.