基础提离及桥墩弹塑性对结构地震反应影响的研究

浅平基桥墩在承受强震作用时其基础与地基之间会发生提离,地基土会进入塑性状态。同时,当结构遭遇设防烈度地震或罕遇地震时,结构往往处于非线性状态,这都会导致桥梁的严重破坏。本文以兰州小西湖黄河大桥为工程背景,采用场地超越概率为10%人工地震波,研究了在弹塑性Winkler地基上同时考虑桥墩塑性时的结构地震反应。通过非线性时程反应分析得到:考虑地基和桥墩的非线性使得桥墩墩顶的位移增大,墩底弯矩减小,这对保护桥墩是有利的;同时得到,小西湖黄河大桥当遭遇罕遇地震(大震)时桥墩已进入屈服,但其屈服曲率不到破坏曲率的1/2,该桥能够满足“小震不坏、中震可修、大震不倒”的设计目标。

Research on Seismic Response of Bridge Structure Considering Uplift of the Foundation and Pier Elasto-plasic

When the bridge piers with shallow foundation subject to strong earthquake action, the uplift of foundations will occur and the foundation soil will enter to plasticity,meanwhile the structure will enter to nonlinear state and is damaged. It is very difficult to simulate the uplift and yield of supporting soil using an accurate method. In this paper,an improved Winkler foundation model, which could be used to consider uplift and yield, is employed in the seismic response analysis. Taking the project of Xiaoxihu Yellow River Bridge in Lanzhou city as the example,an artificial seismic wave with the site transcendental probabity 10% level is inputted and the nonlinear history responses are obtained. The result shows that the displacement on top of the pier increases and the moment at bottom of the pier decreases, the piers will yield when meat strong earthquake, but its curvature will not bead constructure. So the goal of three-level aseismic design can be meat.