In this paper, performance of the abutment-backfill system under thermal variations is studied. For this purpose, a structural model of atypical integral bridge is built considering the nonlinear behavior of the piles and soil-bridge interaction effects. Static pushover analyses of the bridge are conducted to study the effect of various geometric, structural and geotechnical parameters on the performance of the abutment=backfill system under uniform positive thermal variations. It is observed that the intensity and distribution of backfill pressure is affected by the height of the abutment. Furthermore, the internal forces in the abutments are found to be functions of the thermal-induced displacements of the bridge deck, properties of the pile and stiffness of the foundation clay. Using the pushover analyses results, analytical equations are derived to determine the maximum forces in the abutments and maximum length of integral bridges based on the strength of the abutments. Integral bridges with abutment heights less than 4 m, non-compacted backfill and piles oriented to bend about weak axis are strongly recommended to enhance the maximum length limits of integral bridges as determined by the flexural capacity of the abutments. (C) 2004 Elsevier Ltd. All rights reserved.