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地震波是一种多维的随机荷载,一般在参数测定中应将其转化为等效循环荷载。采用有限元模拟多向地震荷载作用下的砂土动力响应,介绍了弹塑性边界面模型及其参数的含义,阐述了确定参数的方法,选取涵盖大震、中震、近场、远场及不同土质条件的155组多向地震输入时程进行单向、多向加载。利用混合效应回归分析法,建立了多向地震荷载作用下等效循环周数计算模型,分析验证了该模型的准确性。提出了基于等效循环周数比的多维地震荷载作用下等效循环周数计算方法。研究表明:模型预测值能较好地反映等效循环周数实际值的变化趋势;震级和震中距对等效循环周数比影响不明显;砂土特性对等效循环周数比的影响具有主导作用,在不同震级范围内,等效循环周数比均随着相对密度的增大而增大,对应于相对密度为45%、60%、80%、100%的砂土,等效循环周数比分别近似为1.60、1.85、1.90和2.05。
Seismic waves are a kind of multi-dimensional random loads, which should be converted into equivalent cyclic loads generally in the determination of parameters. The finite element method is used to simulate the dynamic response of sand under multi-directional seismic loading. The elastic-plastic boundary model and its parameters are introduced. The methods of determining the parameters are described. The models covering large earthquakes, moderate earthquakes, near-field and far- 155 sets of multi-directional seismic input time histories under different soil conditions are unidirectional and multi-directional loading. By using the mixed effect regression analysis method, the calculation model of equivalent cycle weeks under multi-directional seismic loads is established, and the accuracy of the model is verified. A method to calculate the equivalent cycle weeks under the multi-dimensional seismic load based on the equivalent cycle ratio is proposed. The results show that the predictive value of the model can better reflect the change trend of the actual value of the equivalent cycle number; the magnitude and the epicentral distance have no obvious effect on the equivalent cycle number ratio; the influence of sand characteristics on the equivalent cycle number ratio has In the range of different magnitudes, the ratio of equivalent cycles increases with the increase of relative density, corresponding to the relative density of 45%, 60%, 80%, 100% of the sand, the equivalent cycle The weekly ratios are approximately 1.60, 1.85, 1.90 and 2.05, respectively.