Response of full-height frame integral abutments subjected to seismic motions

Abstract

As a new type of bridge, integral bridges can significantly reduce long-term maintenance costs, and their application is encouraged in many countries. However, there is great uncertainty regarding the dynamic performance of full-height integral abutments during earthquakes. This paper presents the findings from a dynamic numerical simulation on a typical full-height frame integral bridge abutment. The influences of peak acceleration, bridge deck length, and abutment height are investigated. The effect of a mitigation method, i.e., installation of a compressible layer behind the abutment, is also discussed. The results highlight the effect of the rigid connection between the deck and the integral abutment, which will transfer the very large inertial force of the bridge deck to the abutment top and cause strong dynamic interaction between the abutment and the backfill. The traditional Mononobe-Okabe method adopted in current bridge abutment design codes cannot provide a reasonable prediction as to the dynamic earth pressure behind integral abutments, leading to unsafe designs. Although a compressible layer can reduce the dynamic earth pressure, the deformation and bending moments of the abutment will increase as a result of the much lower restraint provided by the compressible layer during earthquakes.