Proposed Mathematical Model for Daily and Seasonal Thermal Bridge Displacements

A change in temperature causes a material to change length. Like most structures, bridges are subject to daily and seasonal thermal displacement cycles due to varying temperatures. In conventional bridges, expansion joints and seatings are used to accommodate these displacements. In integral bridges, the expansion joints are eliminated, and this results in rigid connections; hence, the superstructure, the bridge abutments, and the piles undergo varying displacements during each temperature cycle. To understand the temperature-induced soil–structure interactions, a realistic thermal displacement model that considers the realistic temperature variation cycles is necessary. This study discusses first the factors affecting bridge temperature variations and then a practical treatment of these effects in the design stage. The proposed mathematical model for thermal bridge displacement patterns considers the realistic changes in both daily and seasonal temperature cycles over time and the construction temperature. The usability, practicality, and importance of the model are verified by large-scale laboratory tests on segments of a bridge abutment supported by two pile types. The study shows that the proposed method is practical and capable of detecting detrimental effects induced by daily thermal displacement cycles. Potential uses of the proposed method are also discussed via a numerical example in which temperature and thermal displacement patterns measured for a real bridge are compared with estimates from the proposed model. This model was found to compare well with the measured data.