钢筋混凝土梁柱节点区非弹性变形的改进模型研究

Study on modified models for inelastic deformation of reinforced concrete beam-column joints

节点区非弹性变形包括梁端纵筋黏结滑移和节点剪切变形,对钢筋混凝土梁柱组合体的弹塑性受力特征有明显影响。计算采用的节点区非弹性变形本构模型直接影响结构强震反应有限元分析结果的合理性。在纤维模型的基础上,采用在非线性梁柱单元端部附加零长度截面单元的方法,可简便、有效地模拟节点区非弹性变形。基于39个钢筋混凝土中节点和12个边节点的纵筋滑移和节点剪切角的实测数据的显著性分析及非线性拟合结果,提出了可同时考虑梁端纵筋滑移和节点剪切变形影响的σ-sslip-shear本构模型。以4个不同节点参数的梁柱组合体试验为例,对提出的本构模型进行了验证。结果表明:忽略节点区非弹性变形的计算结果明显高估了梁柱组合体的承载力和耗能能力;考虑节点区非弹性变形的计算方法能更准确地模拟梁柱组合体的非弹性受力特征,并能正确模拟随着节点区非弹性变形增大,构件端部的塑性变形向节点区转移的变形特征。

Inelastic deformations of reinforced concrete beam-column joint consist of longitudinal rebar slippage at beam end and shear deformation of joint, which affects the elasto-plastic mechanical characteristics of beam-column subassemblage specimen obviously. The Modeling methods of inelastic deformation of joint will directly influence the rationality of structural response analysis results under strong earthquake excitations. On the basis of fiber model, the modeling method of combining a zero-length section element at the ends of the nonlinear beam-column element could conveniently and effectively simulate the inelastic deformation of joint. Based on the significance analysis and nonlinear fitting results of the measured experimental data of 39 reinforced concrete interior joints and 12 exterior joints, a constitutive model of σ-s slip-shear which could simulate the effect of longitudinal rebar slippage at beam end and joint shear deformation simultaneously was proposed. Four beam-column subassemblage tests with different joint parameters were used as examples to verify the proposed modeling method. The results show that the calculated results of capacity and energy dissipation behavior of beam-column subassemblage is much higher if inelastic deformation of jointis ignored. Inelastic mechanical characteristics of beam-column subassemblage could be simulated more accurately when inelastic deformation of joint is considered, and the deformation characteristics that the plastic deformations will transfer from ends of element to the joint while the inelastic deformation of joint is increasing could also be simulated.