The Role of the Prestressed Tendons on the Seismic Performance of Hybrid Rocking Bridge Bents

Abstract

Abstract. Allowing structural members to uplift and rotate around pre-defined pivot points isolates and relieves the structure from deformation and damage during strong earthquakes. Such rocking behavior has been examined as damage avoidance seismic design for bridges. Rocking structures, either freestanding or hybrid (supplemented with energy dissipation and re-centering devices), have been proposed by several researchers as high-performance systems that can survive major earthquakes without substantial damage. This paper investigates, analytically and numerically, the seismic performance of a hybrid rocking bridge bent which exhibits flag-shaped hysteretic behavior. The rocking frame is enhanced with elastic prestressed central tendons to provide re-centering capacity and hysteretic buckling restrained braces to dissipate energy. The present study examines its seismic behavior under both pulse-type and non-pulse-type ground motions. The focus of the present analysis is on the role of the prestressing force on the seismic performance. The results reveal the diverse influence of prestress. Specifically, prestress is beneficial for small rocking rotations, but could become detrimental when the frame sustains large rotations and as the size of the columns increases. Finally, the results reveal the sensitivity of the different rocking design solutions to the characteristics of the considered ground motion. As a consequence, none of the examined rocking frames can be considered as the optimal design solution under all ground motions. 4983

Modeling of rocking frames under seismic loading

“…[ 27 ] . Giouvanidis and Dimitrakopoulos [ 28 ] worked on the modeling of bridges, and specifically on precast frame structures, equipped with vertical restrainers. Dar et al.…”

“…The beneficial effect of rocking in critical structures (e.g., bridges) has been confirmed by Cheng, [24] and has been also shown by Palermo et al, [25] Wacker et al, [26] and Priestley et al [27] . Giouvanidis and Dimitrakopoulos [28] worked on the modeling of bridges, and specifically on precast frame structures, equipped with vertical restrainers. Dar et al [29] first investigated the seismic response of rocking frames when the contact edge is allowed to reside anywhere between the center of the pier and its extreme edge, while recently they examined the seismic response of rocking frames with unsymmetrical piers.…”