预应力混凝土梁精细化仿真分析关键问题研究

Research on Several Key Problems of Refined Simulation on Prestressed Concrete Beam

结合30m预应力混凝土足尺T梁的破坏试验,利用ANSYS软件对预应力混凝土梁的精细化仿真分析关键问题进行研究。将梁端锚固区腹板部分的混凝土与主梁其他部分的混凝土区分开,仅定义其材料属性为线性,以避免此处因应力集中而过早开裂或压碎,从而影响整体结构的计算收敛性;通过测定试验梁随梁试件的应力应变关系曲线,得到试验梁的混凝土本构关系;按纵筋和箍筋配筋率进行分区段精细化普通钢筋布置;对于混凝土开裂后拉应力的释放按照缓慢释放处理,以防止刚度矩阵过早出现奇异,造成收敛困难;设置足够小的加载步长以及采用完全Newton-Raphson法等实现预应力混凝土梁的三维实体精细化建模和仿真分析。由试验与仿真分析得到的荷载—挠度曲线和裂缝开展情况的对比表明:提出的精细化建模和分析方法准确、有效;仿真求解预应力混凝土梁极限荷载时,可在位移加载、打开混凝土压碎开关和在位移收敛控制条件下进行。

According to the destructive test of full-size 30 m prestressed concrete T-beam,several key issues of refined simulation analysis of prestressed concrete beam were studied by the ANSYS software.The concrete in the web of the anchorage zone at beam end was separated from the concrete in other parts of main beam.Its material property was defined as linear only to avoid here premature cracking or crushing as a result of stress concentration,which would affect the computational convergence of the overall structure.The stress-strain relationship curves of test beam specimens were measured,and the concrete constitutive relation of test beam was obtained.Ordinary steel bars were arranged divisionally and finely in accordance with the reinforcement ratios of longitudinal bars and hoops.The release way of tensile stress after concrete cracking was set to the slow release process,in order to prevent the stiffness matrix from premature singularity,which would result in difficulties in convergence.Small enough load steps were set and full Newton-Raphson method was adopted to realize the 3Dsolid fine modeling and simulation analysis of prestressed concrete beam.The comparisons of load-deflection curves and crack development conditions between test and simulation show that the proposed methods of fine modeling and analysis method are accurate and effective.The ultimate load of prestressed concrete beam can be solved under the conditions of displacement loading,the opening of concrete crushing switch and the control of displacement convergence.