大坝混凝土三维细观力学数值模型研究

在细观结构层次上将大坝混凝土作为骨料、固化水泥砂浆及其粘结界面组成的复合材料,建立了大坝混凝土三维细观力学数值模型。该模型既能够反映混凝土及其细观各相材料在荷载作用下的损伤演化过程,又考虑了动载作用的应变率强化效应。给出了该数值模型求解方法,并编制出能够在普通PC机上运行的串行程序。加载过程既可按荷载控制又可按位移控制。同时,为了减少求解自由度应用了分尺度方法以使最小骨料和固化水泥砂浆混合后其力学性能与一种复合介质等效。通过混凝土湿筛和三级配试件的静、动(冲击)弯拉数值计算验证了本文计算方法和程序正确有效。另外,在串行程序的基础上,优化了刚度矩阵的存储方式,采用双门槛不完全Cholesky分解(ICT)预条件的共轭梯度法(CG),完成了能够在Sun Fire 6800服务器实现并行计算的并行程序改造,从而大大提高了计算效率。

Study on numerical algorithm of 3D meso-mechanics model of dam concrete

On the meso-mechanics level the dam concrete is taken as the composite material consisting of aggregate,mortar and interface between them.A 3-dimensional finite element model of the dam concrete specimen is generated with consideration of damage evolutionary processes and strain-rate effects of the different media.The numerical computing algorithm and its FORTRAN serial program on PC computer for the nonlinear dynamic analysis of dam concrete were developed.The loading procedure can be controlled either by load or by displacement.In order to reduce the degree of freedom of the system,an artificial medium with mechanical properties equivalent to the composite media of the mortar and the finest aggregates were involved by using multi-scaled method.The numerical analyses for the specimens both of wet-sieved and full-graded dam concrete were carried out to investigate the failure processes under static and dynamic shock loading.The analytical results verified that the applied algorithm and its computer program are correct and effective.Based on the serial program,by using memory optimization for stiffness matrix and conjugate gradient(CG) algorithm with the preconditioner of incomplete Cholesky factorization with double threshold(ICT),the parallel program for Sun Fire 6800 server was developed.The computing efficiency was raised remarkably.