框架结构自振频率有限元计算影响因素的研究

通过脉动试验获得土-箱型基础-框架结构(比例1∶2)的自振频率。利用有限元程序Patran建立了四种模型,包括:刚性地基杆系模型、刚性地基实体单元模型、地基A实体单元模型、地基B实体单元模型。利用Nastran程序分五种工况计算了以上四种模型的自振频率,五种工况涵盖了单元类型、网格密度、地基范围、地基刚度、上部结构刚度、结构配筋率等多种因素的影响。结果表明:考虑土-结构动力相互作用时,建模中地基大小取值范围与地基刚度有关,试验模型中梁配筋率对自振频率的影响高于柱配筋率的影响。给出了不同种类场地土条件下刚性地基杆系模型的一阶自振频率调整系数。

Study on factors of FEM analysis in natural frequency for frame structure

The natural frequency of soil-box foundation-frame structure(1:2) was obtained by pulsateon test.Four models were created through FEM program Patran which included framed model with rigid subsoil,solid element model with rigid subsoil,solid element model with subsoil A and solid element model with subsoil B.Program Nastran was adopted to calculate natural frequency of four models in five subcases.The five subcases covered effects of factors such as element type,meshing density,subsoil size,subsoil stiffness,upper-structure stiffness and reinforcement ratio.Results show that when soil-structure dynamic interaction is considered,the range of soil size in FEM modeling is related to the distribution of subsoil stiffness.For different kinds of site soil,the adjusting factors of the first-order frequency in framed model with rigid subsoil are given. In this test model,the effects of beam reinforcement-ratio on natural frequency are larger than that of column reinforcement-ratio.