地震非均匀自由场输入下的拱坝非线性反应分析

Nonlinear responses of high arch dams to nonuniform free field motion due to seismic input

针对高拱坝抗震研究的需要,完成了有限元边界元无限边界元耦合模型地震非均匀自由场输入下的拱坝非线性反应分析。用此模型对溪洛渡拱坝进行计算分析的结果显示:非均匀自由场幅差和相差对拱坝反应有显著的影响,一方面幅差和相差带来结点运动的相互牵掣,降低拱坝主体的响应,另一方面强化了局部扭曲,在某些情况下可能带来局部拉应力和横缝开度的大幅度升高,而且可能会改变坝体动力反应机制和规律。因此对重要的高拱坝抗震设计,有必要考虑横缝非线性、地基辐射阻尼及自由场幅差和相差的影响。

A nonlinear analysis of high arch dams was performed using a compled FE-BE-IBE method with nonuniform free field motion due to seismic loadings. The model can analyze the nonlinear motion of arch dams with contraction joints to analyze the effects of damping due to the infinite foundation and free field input along the canyon. Analyses of the Xiluodu Arch Dam show that the spacial variation of the amplitudes and phases of the nonuniform free field inputs significantly influence the dam responses. The spacial variation will cause the nodes to resist each other and lower the dam motion and the variation can enhance the local distortion and substantially increase the local tensile stresses resulting in joint openings in some cases. The inputs can change the mechanisms and characteristics of the dam dynamic response. Therefore, the aseismic design of high arch dams must consider the effects of the nonlinearity due to joint openings, the infinite foundation damping and the nonuniform free field input along the canyon.