FPS隔震橋樑之耐震評估與位移控制

Abstract

本文探討應用滑動式支承於橋樑隔震的可行性，特別是摩擦單擺支 承。 並針對隔震橋樑上部結構位移過大的問題提出因應對策，包括(一) 以調諧質 塊阻尼器控制、(二)採用「不完全隔震」方式設計。為處理橋 樑在「不完全 隔震」時之結構不對稱性而發展「多支承剪力平衡法」進 行多重支承隔震橋 樑之非線性動力分析。研究結果顯示將樑一端位於橋 台上的支承設計成鉸支 承之「不完全隔震」型式，可使隔震橋樑之耐震 表現大為提昇。不但橋墩受 力大幅折減，橋樑上部結構位移亦很小，毋 須額外之位移控制裝置，不論在 堅硬地盤或軟弱地盤皆然。 In this thesis, the feasibility of using sliding isolation bearings, in particular the Friction Pendulum System (FPS), for aseismic design of bridges is verified through numerical simulations. Although it has been shown that isolation can effectively reduce the forces transmitted to the bridge piers, the superstructure of the isolated bridge may be excessive under low-frequency ground excitations. Two approaches are considered to resolve this problem: one by introducing the Tuned Mass Damper (TMD) for displacement control and the other by providing the bridge superstructure with lateral constraint in one end. A numerical procedure referred to as the "multi- support shear balance method" is developed for nonlinear dynamic analysis of continuous bridges isolated with FPS bearings. Results obtained through extensive numerical simulations indicate that the use of TMD is not sufficient for displacement control of the isolated bridge whereas those with lateral constraints on the superstructure present excellent aseismic performance. Under such configurations, negligible displacements of bridge superstructure are observed while significant reductions of pier shears and moments are achieved without extra displacement control devices. The system performs consistently well in seismic areas of both hard and soft soil-profiles.