土-桩-框架结构非线性相互作用的精细数值模型及其验证

利用有限元软件ABAQUS,建立了土-桩-框架结构非线性相互作用（SSI）的二维精细有限元模型,分别采用记忆型粘塑性嵌套面模型和损伤塑性模型模拟土体和混凝土材料,采用梁单元和rebar单元模拟RC桩基及其内部纵筋,采用接触面对法模拟桩土接触效应,取得了良好的计算效果。将自由场、框架、土-桩-框架结构模型的分析结果和其它成熟的计算软件进行对比,验证了数值模型的有效性。分析发现：桩基外侧靠近承台处的土体的非线性反应很强烈,而桩基内部土体的非线性反应较小,很大程度上只是跟随群桩一起运动。由于桩土动力接触,桩顶的加速度反应可能超出上部结构,并且桩顶的加速度时程曲线上有非常明显的＂针＂状突变。随着地震动强度的增加,上部框架逐渐表现出单自由度体系的动力特征,加速度反应谱有从多个波峰退化为单一波峰的趋势。

Fine Numerical Modeling of Nonlinear Soil-pile-frame Structure Interaction System and Its Verification

A 2D finite element model of soil-pile-frame structure nonlinear interaction was developed using finite element software ABAQUS.Damaged plasticity model and dynamic visco-plastic memorial nested yield surface model were adopted to model concrete and soil respectively.Beam element and rebar element were used to model RC piles and inner longitudinal rebars.A surface-based contact pairs method was used to simulate the interaction effect between soil and piles.The numerical models of free field,frame structure and soil-pile-frame structure were validated by comparing its analytical predictions with other well verified software results.It is concluded that the nonlinear response of soil close to pile cap is very large,while the soil between pile groups has a small nonlinear response and moves with pile groups together to a great extent. The acceleration response of pile cap may be larger than that of the superstructure because of soil-pile interaction effect.In addition,the acceleration histories of the pile cap show obvious spikes.With increase of seismic intensity,the acceleration response spectra show a tendency of degeneration from multiple peaks to single peak which reveals characteristic of single degree-of-freedom system.