Nonlinear finite element analyses of concrete bridge joint systems subjected to seismic actions

Abstract

Following widespread damage to bridge joints in the San Francisco region from the 1989 Loma Prieta earthquake, the necessity for establishing an alternative method for seismic design of bridge joints was identified. Recognizing that conventional joint design practice based directly on shear forces results in congested reinforcement details, which are difficult to implement in practice, a rational design procedure was sought through large-scale testing of bridge joint systems and subsequent finite element and strut-and-tie analyses. The finite element part of the study is presented in this paper, which focuses on (a) identification of compression force flow and thus the load path across the joint, (b) examination of an efficient joint force transfer model, and (c) influence of cap beam prestressing. Combining the experimental and analytical results, a joint design method has been established in which reduction of joint reinforcement was achieved by treating joint shear as part of the complete force transfer across the joint, rather than as an independent action. The proposed design approach has been validated in a laboratory test on a full-scale multiple-column bridge bent.