Dynamics and seismic performance of rocking bridges accounting for the abutment‐backfill contribution

Abstract

Summary The present study explores analytically the concept of rocking isolation in bridges considering for the first time the influence of the abutment‐backfill system. The dynamic response of rocking bridges with free‐standing piers of same height and same section is examined assuming negligible deformation for the substructure and the superstructure. New relationships for the prediction of the bridge rocking motion are derived, including the equation of motion and the restitution coefficient at each impact at the rocking interfaces. The bridge structure is found to be susceptible to a failure mode related to the failure of the abutment‐backfill system, which can occur prior to the well‐known overturning of the rocking piers. Thus, a new failure spectrum is proposed called Failure Minimum Acceleration Spectrum (FMAS) which extends the overturning spectrum put forward in previous studies, and it differs in principle from the latter. The comparison with the dynamic response of bridges modelled as rocking frames without abutments reveals not only that seat‐type abutments and their backfill have a generally beneficial effect on the seismic performance of rocking pier bridges by suppressing the free rocking motion of the frame system, but also that the simple frame model cannot capture all salient features of the rocking bridge response as it misses potential failure modes, overestimating the rocking bridge's safety when these modes are critical.

Shake table statistical validation of Finite Element models of rocking structures

“…Rocking is also a promising seismic response modification technique, both for bridges and buildings, with limited practical applications in the former USSR and New Zealand [20,21]. Applications in buildings may comprise a soft-rocking-story mechanism [22][23][24], or a rocking wall [25,26], whereas in bridges, rocking piers [27][28][29][30][31][32][33][34][35]. Several analytical studies investigated the response of rocking structures combined with external dampers or…”

Non-linear spectrum-based analysis of rocking structures

“…Rocking has been proposed as a seismic isolation method for both bridges [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and buildings [21][22][23], because uplift works as a mechanical fuse and limits the design forces of both the superstructure and the foundation. Unlike structures designed to yield, the free rocking rigid block exhibits negative post-uplift stiffness [24].…”

Dynamic Response of Multi-Storey Structures Seismically Isolated Using Kinematic Bearings

“…The dynamic response of rigid blocks rocking on a rigid ground was first studied by Housner [1], who highlighted the parameters that affect the stability of rigid bodies which can be uplifted under horizontal excitations. Since then, with the recognition of the remarkable properties of the rocking response, various forms of rocking systems have been studied, such as flexible rocking oscillators on solid [2][3][4][5][6] and flexible ground [7,8], rocking structures on the foundations [9], rocking bridge piers [10][11][12], rocking frames [13][14][15][16][17], coupled conventional structures with rocking walls [18][19][20] and seismic isolation by forming a rocking floor at the base [21][22][23][24]. Despite the remarkable stability of free-to-rock large-scale systems, the basic requirement for the practical application of rocking systems is the prevention of overturning [25].…”