基于结构精细化模拟分析平台的弯剪纤维单元模型

为模拟钢筋混凝土柱在轴力、剪力和弯矩耦合作用下的非线性滞回特性，利用显式中心差分法，建立一种基于显式算法的弯剪纤维单元模型，并引入到结构精细化模拟分析（RSAPS）平台中。该模型基于Timoshenko梁理论，材料模型选用基于修正斜压场理论（MCFT）的二维钢筋混凝土本构模型。应用RSAPS平台分别模拟往复荷载作用下发生弯曲、弯剪和剪切破坏的钢筋混凝土柱的滞回性能，并将分析结果与试验和未考虑剪切变形的纤维单元模型模拟结果进行对比。结果表明：对于发生弯曲破坏的构件，由于剪切变形较小，未考虑剪切变形的纤维单元和弯剪纤维单元均可以较好地模拟构件的滞回性能；而对于发生弯剪破坏和剪切破坏的构件，采用未考虑剪切变形的纤维单元模型，会高估构件的初始刚度和耗能能力，也会高估其受剪承载力；而所提出的弯剪纤维单元模型能较好地模拟构件的刚度和承载力退化，同时，也能较好地模拟滞回曲线中的捏缩现象，模拟结果与试验结果吻合较好。

Refined simulation analysis platform of structures-basedflexure-shear fiber element model

In order to simulate the nonlinear hysteretic behavior of reinforced concrete (RC) columns under a combined loading of axial force, shear force and bending moment, an explicit algorithm based flexure-shear fiber element model using the explicit central difference method was proposed and implemented in the refined simulation analysis platform of structures (RSAPS). The model was based on the Timoshenko beam theory, and the material model used the 2D reinforced concrete constitutive model based on the modified compression field theory (MCFT). The hysteretic behavior of RC columns with flexure, flexure-shear and shear failure was simulated using the RSAPS, and the simulation results were compared with experimental results as well as the simulation results using the flexure fiber element ignoring the shear deformation. It is found that for RC columns with flexure failure, both the flexure fiber element ignoring the shear deformation and the developed flexure-shear fiber element can simulate the hysteretic behavior well because of small shear deformation. However, for RC columns with flexure shear and shear failure, analytical results using the flexure fiber element ignoring the shear deformation tends to overestimate the initial stiffness, energy dissipation and shear strength, while the developed flexure-shear fiber element is able to capture the behavior of stiffness and strength degradation as well as pinching of the hysteretic curves. The response predicted with the developed flexure-shear fiber element shows a very good correlation with the experimental results.