Seismic fragility estimation of cable-stayed bridges with various pylon shapes considering soil-pile interaction

Cable-stayed bridges (CSB) are widely acknowledged among other bridge types owing to their attractive appearance and greater flexibility. Numerous research initiatives have been undertaken for the seismic fragility assessments (SFA) of CSB. Nonetheless, the pylon shape influence on seismic performance remains an intriguing area of study. The current research performs the SFA of A-shape, Diamond shape, H-shape, and inverted Y-shape pylon CSB to evaluate seismic vulnerability under uncertain seismic excitations considering soil-pile interaction. The SFA illustrates the possible damage of CSB as a function of strong ground motions and can be used to evaluate the extent of damage probability for a specific ground motion index. Spectral acceleration has been adopted as the optimal intensity measure. An array of strong ground motions were used to evaluate CSB for the Indian seismic zone-V with stiff clayey soil. The Finite Element modeling approach has been employed for the simulation procedures. The pylon drift ratio and the bearing displacement have been used as engineering demand parameters. The fragility curves were developed using incremental dynamic analysis for four performance levels. The overall system fragility of CSB has been derived using the Riemannian Manifold Hamiltonian Monte Carlo-based subset simulation. The analysis results indicate that deck-pier connections, i.e., bearings, are the most fragile components, and their placement and mechanical properties significantly impact system fragility. Boundary limits and system fragility curves demonstrate that the inverted Y-shape and the Diamond shaped pylon CSB perform well with minimal collapse probability.