Seismic Analysis of a Long-Span Self-Anchored Suspension Bridge with Rigid Cable Towers Based on Shaking-Table Tests

Long-span self-anchored suspension bridges (SAS) with rigid cable towers are intricately designed to satisfy the aesthetic standards of structural design. Unlike the traditional arrangement of bridge towers and main girder, the ellipse-shaped bridge tower runs parallel to the longitudinal girder and exhibits significant variations in stiffness in the longitudinal and transverse directions. There is an internal force redistribution of the girder between the main and side spans during seismic excitations relative to static equilibrium. These unique bridge designs induce striking spatial impacts; earthquakes can potentially result in intricate and unforeseeable reactions within the entire structure. To understand this better, a shaking table test was performed on a 1/50 scale model of a long-span self-anchored suspension bridge with rigid cable towers to analyze its seismic response. The full-bridge model was tested on a dual-shaking-table system to investigate its seismic response under consistent excitation in various input directions. The test results confirmed the accuracy of the test model based on its comparison with a finite element model (FEM). The main tower exhibited the most significant transverse displacement change at the top relative to the base, with the largest strain responses observed near its waist. The vertical acceleration peak of the bridge was substantially greater than that in the horizontal direction owing to the large main span and the involvement of the third mode in the bridge model. Furthermore, the bridge model experienced a higher average variation in the suspender force under longitudinal and vertical excitations than under transverse and vertical excitations. These study findings provide insights into improving the structural designs of modern SAS, thereby ensuring better resistance to earthquake excitations.