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高级分析中的塑性区分析方法,采用壳单元模拟,能最准确地分析钢框架的极限承载力及性能。但这种全壳塑性区模型的缺点是:计算量很大,仅限于求解小型结构。通用有限元软件中的梁单元能模拟残余应力并能描述塑性发展状况,但不能模拟可能导致结构破坏的板件局部屈曲性能。采用一种混合模型,仅在容易发生线性或非线性局部屈曲的位置采用壳单元模拟,在其他位置采用梁单元模拟,这样能避免全梁单元模型的弊端。这种混合模型的关键是,首先要确定各单元的位置、壳单元区域的长度,且梁单元与壳单元的连接位置不产生应力集中和位移不协调。除了解决这些问题,还通过研究它在结构中的性能,系统地评估混合模型。混合模型的承载力平均计算误差仅为0.91%,但能比全壳塑性区方法节约83%的计算时间。
The plastic zone analysis method in advanced analysis, using shell element simulation, can most accurately analyze the ultimate bearing capacity and performance of steel frames. However, this full-shell plastic zone model has the disadvantage of being computationally intensive and limited to solving small structures. Beam elements in general finite element software can simulate residual stress and describe the state of plastic development, but can not simulate the local buckling behavior of the plate which may lead to structural failure. Using a hybrid model, shell element simulation is used only where linear or nonlinear local buckling is likely to occur, and beam element simulation is used elsewhere, which avoids the disadvantages of a full beam element model. The key of this hybrid model is to determine the position of each unit and the length of the shell unit area first, and the connection between the beam unit and the shell unit does not produce stress concentration and uncoordinated displacement. In addition to solving these problems, the hybrid model is systematically evaluated by studying its performance in the structure. The average calculation error of the mixed model is only 0.91%, but it can save 83% of the calculation time than the plastic shell method.