With the growing demand for transportation infrastructure in the central and western regions of China, long-span single-tower cable-stayed bridges with steel-concrete hybrid girders have become a superior aesthetic and economical solution for spanning deep valleys in mountainous areas. However, such bridges usually have significantly asymmetric span arrangements, leading to complex dynamic behavior under seismic conditions. Meanwhile, the frequent occurrence of strong earthquakes in these regions poses a great challenge to their seismic safety, and research on their reasonable lateral seismic isolation systems remains insufficient.
Therefore, Shichun ZHANG, Junjun GUO, Wei LIU, Jibo LI, and Zhongguo GUAN from Tongji University and China Highway Engineering Consulting Co., Ltd. have jointly carried out a research entitled “Investigation on Lateral Seismic Isolation System of a Typical Long-Span Single-Tower Cable-Stayed Bridge for Mountainous Areas”.
This study takes the Jinsha River Bridge as the research object, deeply analyzes the significant structural asymmetry of long-span single-tower cable-stayed bridges and its influence on structural seismic responses. A multilinear model composed of an ideal elastoplastic element and a multilinear elastic element was used to simulate different hysteresis behaviors, and a parametric analysis was conducted to explore the appropriate damping hysteresis for the lateral seismic isolation of such bridges. The results show that the inverted S-shaped hysteresis has a relatively smaller secant stiffness, which can help balance the large difference in lateral stiffness between towers and piers, thereby achieving more efficient damping effects and reducing the base shear force of towers and piers. Additionally, an influence matrix-based method was adopted to determine the reasonable yield force of dampers in the lateral isolation system, and a correlation was found between this yield force and the shear force of corresponding bearings in the lateral fixed system. Furthermore, the study investigated the influence of geological conditions (including different terrain and site conditions) on the reasonable lateral isolation system. It is suggested that when the side span crosses a steep valley slope, dampers should be installed at all tower and pier positions; when the side span crosses a gentle valley slope, a lateral isolation system without dampers at auxiliary piers can be used. Compared with hard sites, soft sites require larger damper yield forces and will cause greater seismic responses.
The paper “Investigation on lateral seismic isolation system of a typical long-span single-tower cable-stayed bridge for mountainous areas” authored by Shichun ZHANG, Junjun GUO, Wei LIU, Jibo LI, Zhongguo GUAN. Full text of the paper: https://doi.org/10.1007/s11709-025-1132-4.