Seismic Assessment of Rocking Bridge Bents Using an Equivalent Rocking Block * Elias G. Dimitrakopoulos 1 , Matthew J. DeJong 2 , Anastasios I. Giouvanidis 1 1 Department of Civil & Environmental Engineering, The Hong Kong University of Sci- ence and Technology, Kowloon Bay, Hong Kong 2 Department of Engineering, University of Cambridge, Cambridge, UK ABSTRACT In light of the resurgence of rocking as a means of seismic isolation for modern structures/bridges, there is an increasing need to predict the response of complex rock- ing structures. To date, most analytical investigations into the rocking behavior assume a simple model involving a single rigid rocking block on a rigid half-space. This paper proposes the prediction of the rocking response of a complex (multiple block) rocking structure by considering the response of a single rigid rocking block. In particular, it de- scribes a methodology to derive a dynamical equivalence between a planar rocking bridge bent and the archetypal rocking block. Through the proposed concept of the (dynamically) equivalent rocking block, this approach makes the vast existing research on the rocking block useful for the treatment of more realistic rocking structures. To in- vestigate the efficient of the proposed approach, the study assesses the seismic re- sponse of a bridge bent designed to rock during earthquake excitation. The results verify the ability of the proposed approach to capture the global rocking behavior and confirm the ample seismic stability of the symmetric planar rocking bridge bent. Keywords: rocking bridges, equivalent rocking block, structural dynamics, earthquake engineering 1. INTRODUCTION The idea of allowing rocking behaviour as a means of seismic isolation is not new. Early studies and applications on rocking date back to the 60’s and the 70’s (Housner 1963, Kelly and Tsztoo 1977). Recently, the concept of re-centering structures, which use some degree of rocking motion to isolate a structure from the stresses induced by earthquakes, is re-gaining momentum as a modern seismic design alternative. In this context, numerous studies on the rigid rocking block have generated a wealth of knowledge about rocking behaviour. However, there is still a need to predict the ex- pected response and assess the seismic performance of modern and more complex rocking systems, such as rocking bridge bents (frames). 3653