Evaluation of the Performance of Expanded Polystyrene Block on the Reduction of the Deck Cracking in Wide Integral Abutment Bridge

Longitudinal joints are thought to provide relief from expansion and contraction of the bridge deck owing to temperature change, shrinkage, and live loads, especially for a wide bridge. Historically, however, these joints have been known to leak, allowing chloride-laden water to reach the bottom of the deck overhang and even the exterior girders. Research conducted by Phares et al. indicated that the development of cracking in bridge decks seems less dependent on the total width of the deck and more so on internal restraint of the abutment to temperature changes and, in particular, gradients. Based on the finite element method (FEM) results, an effective solution to reduce cracking in the deck might be to place an isolation pad between the soil and the back side of the abutment. The primary objective of this paper is to investigate the effectiveness of an isolation foam block at the back of an integral abutment in reducing the stress-induced strain and the deck end longitudinal and diagonal cracking near the end of the deck with an integral abutment. To achieve this objective, a highway bridge (Viking Road Bridge) in Iowa, US, designed with a width of 228 ft, was selected for the study. The bridge deck has no longitudinal joints but, based on the previous research results, it was equipped with thermal isolation pads behind the abutment. The newly constructed bridge was monitored for over two years, and this was followed by multiple bridge inspections. An analytical study was conducted to investigate the efficiency of the isolation foam on the bridge deck end structural behavior. The results indicated that the thermal isolation foam is effective in reducing the temperature gradient through the abutment thickness, especially on extremely cold days. By reducing the temperature difference between the abutment and the deck, a thermal isolation block is effective at reducing the deck end strain and resisting deck end cracking. The FEM results indicated that the maximum deck stress-induced strain was 46% greater without the effects of the thermal isolation block and greater than the concrete cracking strain. This indicated that, without the thermal isolation pad, the Viking Road Bridge could crack at the end of its deck.