摘要
在土-结相互作用分析中,一般假定基础为刚性。这种假定在基础尺寸较小,或地震波频率较低时,有一定的合理性;但当基础尺寸大于入射地震波最小波长时,刚性基础对高频地震波具有较大的滤波作用,影响结构反应的计算精度,应该考虑基础的柔性。本文考虑基础的柔性,将土-基础-结构体系进行分区计算,土体和基础采用集中质量显式有限元方法,半无限土体采用多次透射人工边界模拟,通过FORTRAN自编程序进行分析;上部结构采用隐式有限元法,可通过ANSYS进行分析;当结构采用梁单元时,通过约束方程对基础和结构进行耦合连接;结构和土体可采用不同的时间步距,实现了柔性基础情形的土-结构相互作用分区异步计算。通过与Belytschko显-隐式同步算法对比,表明本文时空分区显-隐式结合异步算法,在保证精度的前提下,可极大提高计算效率。进一步通过柔性基础和刚性基础的算例对比,验证了所模拟的最小波长远大于基础尺寸时,刚性基础假定较为合理,并简单讨论了计算中出现的失稳现象。
In the analysis of soil-structure interaction,the foundation is generally assumed to be rigid.This assumption is reasonable when the size of foundation is small or the frequency of seismic wave is low,but when the size of foundation is larger than the minimum wavelength of the incident seismic wave,the rigid foundation has a great filtering effect on the high frequency seismic wave,which influences the accuracy of the structural response,so the flexibility of the foundation should be considered.In this paper,considering the flexibility of the foundation,the soil-foundation-structure system is calculated in partitioned way.The soil and foundation are analyzed by lumped-mass explicit finite element method,and the unbounded soil is modeled by transmitting boundary,which is analyzed through the FORTRAN program;the upper structure is analyzed by the implicit finite element method through ANSYS.When the beam element is used in the structure,the foundation and the structure are coupled by the constraint equation.The structure and soil can use the different time step to realize partitioned asynchronous calculation of soil-structure interaction under flexible foundation.By comparison with the Belytschko explicit-implicit synchronization algorithm,it shows that the proposed algorithm in this paper can greatly improve the computational efficiency on the premise of ensuring the precision.Furthermore,through the comparison between the flexible foundation and the rigid foundation,it is proved that the rigid foundation assumption is reasonable when the simulated minimum wavelength is larger than the size of foundation.The phenomena of instability in the calculation are discussed briefly.
作者
陈少林
陆新宇
赵宇昕
CHEN Shaolin;LU Xinyu;ZHAO Yuxin(Department of Civil and Airport Engineering,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China)
出处
《自然灾害学报》
CSCD
北大核心
2020年第3期9-19,共11页
Journal of Natural Disasters
基金
国家自然科学基金项目(51978337)。
关键词
土-结构动力相互作用
显-隐式结合异步算法
多次透射边界
柔性基础
刚性基础
soil-structure dynamic interaction
explicit-implicit algorithm
multiple transmitting boundary
flexible foundation
rigid foundation
