纜索支撐橋梁受風力穩定性及超長跨徑橋梁系統研究

Abstract

纜索支撐橋梁以其優美的外觀及卓越的張力結構特性，常作為長跨徑橋梁及地標式橋梁的最佳解決方案。本論文主要建立一套數值分析方法，來探討纜索支撐橋梁受風力時的穩定性，並對超長跨徑橋梁系統之可行性進行初步研究。本文首先建立一個兩節點懸鍊吊索元素，考慮柔性、大變位、及端部之剛度效應，並結合梁及桁架元素，以進行纜索支撐橋梁之幾何非線性分析，及受風力之穩定性分析。此外，在執行結構分析之前，並先就單根吊索的無應力長度及多段吊索之形狀進行計算。 針對纜索支撐橋梁受風力穩定性，本文提出一完整的二階分析法，分別考慮靜載重及風載重之個別效應，可計算纜索支撐橋梁出現氣靜力及氣動力不穩定之臨界風速，以確保橋梁之最大設計風速在使用年限內不會被超越。本文接著進行超長跨徑橋梁系統之可行性研究，純粹就學術角度，探討台灣海峽跨海大橋在技術上之可行性。 本研究可視為一個初始的努力，以建立數個副程式，來進行纜索支撐橋梁不同功能之結構分析，包含吊索形狀分析、幾何非線性分析、空氣靜力不穩定及空氣動力顫振分析。

Cable-supported bridges with an elegant outlook and efficient structural performance through use of tension members provide a good solution for long-span bridges and landmark bridges. In this dissertation, a numerical method analysis procedure was developed to investigate the wind-induced instability of cable-supported bridges, and to conduct a feasibility study for super-long span bridges. First, a two-node catenary cable element considering the flexibility, large displacements, and rigid-end effect is derived. Such an element was used along with the beam and truss elements in the geometric nonlinear analysis of cable-supported bridges considering wind-induced instability. Prior to execution of structural analysis, the unstressed length of each cable is calculated and cable shape analysis is performed for single cables and multi-segment (suspension) cables. With regard to wind-induced instability on cable-supported bridges, a two-stage technique of analysis is adopted to account for the effects of dead loads and wind loads, respectively. By such a technique, the critical wind speeds of aerostatic instability and aerodynamic instability are determined. Such information serves as a good reference for ensuring that the maximum design wind speed won’t be exceeded during the service life of the bridge. Finally, various structural systems for super-long span bridges are investigated. From the academic point of view, a preliminary feasibility study is proposed for the Taiwan Strait Crossing Bridge. As part of the result of the present study, several subprograms for dealing with various functions of analysis for cable-supported bridges were developed, including the ones for the cable shape analysis, geometric nonlinear analysis, aerostatic instability analysis, and aerodynamic flutter analysis.