本文以雙塔對稱斜張橋為例,應用有限元素法建立二維、三維分析模型,並利用電算程式進行斜張橋靜、動態分析比較,探討地震力作用下結構體動態結構行為。分析時考慮非線性樑柱效應、纜索中垂效應和大變位效應之影響。首先進行初形分析找出合理之初形位置及預力分佈,以此初形位置進行振態分析、變形分析、地震力分析。文中選用集集地震(TCU084日月潭氣象站測站)為地震荷載,考慮不同方向之地震力輸入,觀察超大跨距斜張橋在強震作用下之結構行為。數值分析結果顯示,在水平順橋向地震力作用下,歷時過程中大樑振動均以反對稱之形式出現,大樑中點幾乎無位移產生,考慮大變位效應後非線性效應較為明顯,大樑中點開始出現位移;垂直向地震力作用下大樑振動均以對稱之形式出現。
A finite element computation procedure for static and dynamic analysis of 2-D and 3-D long-span cable-stayed bridge under action of seismic loads is presented in the study. The Three Span Twin Tower Symmetric Cable-Stayed Bridge is taken as example. The system equation of cable-stayed bridges including the nonlinearities due to beam-column, cable sag and large displacement effects are considered. First of all, the initial shape of cabled-stayed bridge is determined by using shape iteration technique. Based on the initial shape the deflection, natural frequencies and modes and dynamic responses seismic action are determined. The numerical results show that the vibration of girder appears in the form of anti-symmetry under horizontal X seismic excitation. The mid point of girder has no displacement. After considering the large displacement effect, the non-linear effect is comparatively obvious. The vibration of girder appears in the form of symmetry under vertical seismic excitation.