Numerical investigation of transverse steel damper (TSD) seismic system for suspension bridges considering pounding between girder and towers

Transverse steel damper (TSD) is a promising passive control device used for seismic isolation and has been validated to feasibly balance the girder transverse seismic displacement and inertial force in cable-stayed bridges. However, for the TSD system, transverse pounding could occur at the locations of girder and tower legs when the gap size is insufficient to accommodate the girder-support transverse relative displacement under major earthquakes. Transverse pounding can significantly affect the dynamic responses of bridge structures, hence, the present paper investigates the effectiveness of TSD as a control strategy for transverse seismic responses in long-span bridge structures (i.e., suspension bridges), accounting also for the influence of the pounding effect in the dynamic response analysis. A typical suspension bridge is considered for case study purposes, and four transverse girder-support connection systems are investigated, including the conventional fixed and sliding-free connections and the TSD connections with and without pounding effect. A comprehensive comparison of the seismic performance among these transverse restraining systems is conducted through Incremental Dynamic Analysis and fragility analysis. Additionally, the effect of seismic-induced pounding in the TSD system is assessed from an energetic point of view. The results show that, for the suspension bridge with TSDs as the transverse control strategy, a satisfactory balance between force and displacement demands can be obtained in small-to medium-intensity earthquakes. However, the pounding between the girder and tower legs during large-intensity earthquakes can substantially increase the seismic demands in the tower legs