Physical model investigation of a hybrid GRS integral bridge abutment under cyclic thermal stresses

GRS integral bridge abutments develop large lateral earth pressure on the facing during seasonal/diurnal thermal expansion/contraction, causing significant surface settlements. To mitigate these issues, researchers prefer the use of different kinds of facing to withstand lateral pressure in conjunction with reinforcing of backfill to reduce surface settlement. The present research investigates the performance of a hybrid integral abutment under lateral movement of the facing due to cyclic thermal expansion/contraction of the bridge deck through scaled down 1 g physical model tests. Using the optimized facing and reinforcement configuration, an integral abutment model was proposed and analyzed under varying rate of loading and different loading offsets for three displacement modes till 100 cycles of excitation. The assessment included the development of lateral pressure on facing, surface settlement, magnitude and location of peak reinforcement forces, followed by evaluating long-term performance in terms of permanent strains, stiffness degradation, and strain energy dissipation. The observations revealed that the proposed model having strong connection between the reinforcement and facing along with inclusion of secondary reinforcements along the entire height of abutment in the bearing zone exhibits rapid dissipation of accumulated strain energy, leading to a 48 % reduction in surface settlement under cyclic thermal stresses.