基于UPFs的粘弹性人工边界单元及地震动输入方法研究

Research on UPFs-based viscoelastic artificial boundary element and ground motion input method

基于粘弹性人工边界相关理论和地震动输入方法的有关理论,推导并建立了既具有粘弹性人工边界特性,同时可以将地震动转化为施加在人工边界上等效荷载的三维粘弹性人工边界,并利用二次开发工具UPFs将其成功地嵌入至通用有限元分析软件ANSYS中。通过Lamb表面源问题以及内源问题对上述二次开发单元进行了验证。算例表明,该单元可以很好地对无限地基辐射阻尼进行模拟。随后通过对自由场波动输入问题的验证,表明该单元可以实现在有限元单元级别上准确有效地施加地震动等效荷载。与传统的粘弹性边界施加方式相比,该单元有着更简单的使用性以及更强的操作性,同时又不增加计算模型的规模等优势,因而计算效率更高。同时,结合通用有限元分析软件ANSYS强大的建模和计算分析能力,使粘弹性边界有着更广泛的应用,并可适用于各种结构-地基动力相互作用问题的分析。

Based on the theories of viscoelastic artificial boundary and seismic wave input method, a 3D viscous- spring artificial boundary was established, which has characters of viscous-spring artificial boundary and can trans- form seismic wave to equivalent load applied on the artificial boundary, and embedded in the generalized finite ele- ment software ANSYS by User Programmable Features （UPFs）. This secondary developed element was verified by Lamb surface problem and inner source problem to prove that the element can simulate infinite foundation radiation damping. Then the results of free field seismic wave input problem shows that the element could realize the input of seismic wave equivalent load very well and accurately on finite element level. Compared to the traditional applying method of viscous-spring boundary, the element is used more easily and more powerful in operability. Meanwhile it has higher computational efficiency for not increasing the scale of the modal. Moreover, combined with the powerful ability of modeling and calculation of generalized finite element software ANSYS, the element makes viscous-spring artificial boundary used more widely and suitable for the analysis of Structure-Foundation Interaction.