[关键词]
[摘要]
传统坝体地震易损性评估所采用的非线性数值模拟手段的计算量很大,为兼顾大坝地震易损性评估的高效 性与准确性,提出基于增量动力分析(incremental?dynamic?analysis,IDA)与多层感知机(multilayer?perceptron,MLP) 的混凝土坝地震易损性评估方法。以我国西北地区某混凝土重力坝为例,建立三维坝体-库水-地基有限元模型并 开展多组地震响应计算。利用等步长调幅处理所选地震动记录,并采用三向地震进行幅值输入;选取峰值 [地 面] 加速度(peak?ground?acceleration,PGA)为地震动强度指标,坝顶顺河向位移为大坝损伤指标,初步进行混凝土 坝易损性分析。提取各地震动特性参数作为输入,坝顶顺河向位移为输出,训练并测试 MLP 模型;扩充地震动以 获取各地震动特性参数,利用 MLP 模型进行坝顶顺河向位移的快速预测,实现有限元结果的扩充,进行混凝土坝 易损性分析,并绘制易损性曲线。结果表明,将 MLP 模型引入分析可有效扩充数据量,利用 IDA-MLP 耦合方法 建立的大坝地震易损性曲线符合实际规律,验证了采用 MLP 模型预测混凝土坝损伤指标进而扩充数据的可行性, 在保证精度的情况下大幅提高计算效率,为同类型水工建筑物的抗震安全评价和防震减灾提供科学依据。
[Key word]
[Abstract]
The western region of China is rich in hydropower resources, but strong earthquakes occur frequently. Hydraulic structures may withstand strong earthquakes during their life cycle. The damage caused by earthquakes will affect the normal operation of water conservancy projects, which seriously threatens people's lives and social stability. The seismic vulnerability analysis provides the seismic basis for seismic design of hydraulic structure and earthquake prevention and disaster reduction, which is very important to ensure the expected performance of concrete gravity dam and safe operation under earthquake.The seismic vulnerability assessment of dams often requires the use of nonlinear numerical simulation methods and a huge amount of calculation work. Considering the efficiency and accuracy of seismic vulnerability assessment of dams, a way based on incremental dynamic analysis and multilayer perceptron for seismic vulnerability assessment of concrete dams is proposed. Taking a concrete gravity dam in northwest China as an example, a three-dimensional finite element model of dam body-reservoir water-foundation is established and multiple seismic response calculations are carried out. The selected ground motion records are processed by equal step amplitude modulation, and the amplitude input is carried out by three-way seismic. The peak ground acceleration is selected as the index of ground motion intensity, and the displacement of dam top along river is selected as the index of dam damage. The multilayer perceptron model was trained and tested by extracting the vibration characteristic parameters as input and the displacement of dam top along river as output. The ground motion is extended to obtain the vibration characteristic parameters. The MLP model is used to quickly predict the displacement of the dam top along the river, and the finite element results are extended. The vulnerability analysis of the concrete dam is carried out, and the vulnerability curve is drawn.The results are as follows:(1)The seismic vulnerability of concrete gravity dam is analyzed based on incremental dynamic analysis method. Incremental dynamic analysis's curve clusters of river-side displacement, transverse river flow displacement and vertical displacement of the dam crest are plotted, and seismic vulnerability curves are plotted. In summary, the earthquake damage grade of the selected gravity dam under the designed ground motion is low, and about 80% probability belongs to the basically intact state.(2)The multi-layer perceptron model is introduced into the incremental dynamic analysis method, and the seismic vulnerability analysis method of concrete gravity dam based on incremental dynamic analysis-multi-layer perceptron is proposed. After the training of the multi-layer perceptron model, the accuracy of the damage prediction index is higher. The coefficient of determination is 0.960 2, the mean square error is 0.005 6, and the mean absolute error is 0.056 1. Based on this method, more analytical data can be constructed to expand the finite element dynamic calculation results. It saves the calculation work up to 75% and reduces the nonlinear dynamic calculation time. The seismic vulnerability of dams can be predicted quickly and accurately as close as possible to the reality, and the vulnerability curve can be drawn to improve the efficiency of seismic vulnerability analysis of dams.
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