Seismic performance assessment and retrofitted by buckling-restrained braces for half-through concrete-filled steel tubular arch bridge with the vertical suspended deck system

Arch bridges with vertical suspended deck systems have been constructed during the last 30 years, different from the existing arch bridges with longitudinal beams or panel beams. The latter have better the seismic inertia forces can be transmitted to the piers or foundations through both the arch rib and the longitudinal beam. However, for arch bridges with vertical suspended deck systems, seismic inertia forces produced by deck systems are transmitted to arch ribs by the geometric nonlinearity of suspenders firstly, and then further transmitted through the arch ribs to the piers or foundations, resulting in greater seismic demands on the arch ribs. In this paper, the seismic performance and weak structural elements of the half-through concrete-filled steel tubular (CFST) arch bridge with a vertical suspension deck system under tri-directional ground motions were studied by numerical simulation, and the bridge model was primarily verified by a static loading test conducted in situ. Moreover, Buckling-Restrained Braces (BRBs) were strategically placed to optimize their seismic mitigation effects by systematically analyzing the bridge’s seismic response. The results identify the arch foot, the 1/8 point of the arch rib, the arch crown, and the transverse bracing as weak structural elements for seismic resistance of the half-through concrete-filled steel tubular (CFST) arch bridge with a vertical suspension deck system. Therefore, a thoughtfully designed arrangement of BRBs targeting the seismic weak structural elements can significantly increase the values of capacity demand ratio (CDR) for weak structural element, thereby strengthening the seismic safety margin of the bridge.