Study On Dynamic Characteristic And Aseismic Performance Of Long-Span Tied-Arch Bridges

A tied-arch bridge is a composed structure which consists of arches and ties,which characterized by the horizontal thrust of arch ends being balanced by its ties. Therefore, the tied-arch bridge can break the limit of high request for piers, abutment and groundsill in arch bridges with thrust, thus improving greatly its applicability under different field conditions and then the tied-arch bridge is broadly applied home and abroad.As a result of the high center of gravity and huge mass, piers in long span tied-arch bridges suffer from much greater seismic effects than common beam bridges. Consequently, it is indispensable to implement the aseismatic design. Nowadays, studies on the dynamic and aseismatic performance of tied-arch bridges mostly focused on individual cases, but the systematic researches is lacking. Therefore, sponsored by Natural Science Fund of JiangSu province, a few aspects are studied in this paper as follows. 1. Aseismatic design characteristics of tied-arch bridges are discussed and the aseismatic design process is brought forward.2. By comparative studies, the influence of changes in structural style of arches and hangers on dynamic characters and structural performance of tied-arch bridges is systematically investigated. Based on it, some suggests are presented, which possess the meaning of guide for bridge style selection. Studies demonstrate that the out-plane incline of arches will enhance the transverse stiffness, while the incline of hangers will enhance the in-plane stiffness of tied-arch bridges. The increase of the stiffness will enhance the internal force of tied-arch bridges.3. For longitudinal isolation design of long span tied-arches, a new isolation method combing viscous fluid damper and slip basin bearings is brought forward. Moreover, the damping coefficient C is analyzed. In the end, the influence of piers'height on the seismic response and isolation effects of tied-arch bridges using dampers are discussed. Studies show that the structural seismic response is enormously minished by utilizing viscous dampers and the damping coefficient C has great effects on the isolation performance, which denotes that the parametric analysis is essential for the isolation design. Besides, researches also indicate that with the increase of the piers'height, there exists some decline in the structural seismic response and the isolation effect totally has a descending trend.4. As to transverse isolation design of long span tied-arches, four different layouts of viscous dampers'place are put forward and further compared on their isolation effects. Accordingly, the layout that dampers are laid between cap beams on piers and ending cross beams is recommended firstly. Studies indicate that with the increase of piers'height, the transverse seismic response appears to decline and the isolation effect of the upside structure and piers near the fixed bearings is improved.