当前经常采用的混凝土中氯离子扩散分析的有限元法在计算混凝土试件暴露于氯盐环境的初期时,试件较深处的氯离子浓度的有限元法计算结果时常会发生振荡或甚至出现浓度负值等不合理的情况。利用数值积分近似计算的梯形公式,研究建立了氯离子扩散有限元方程中的集中浓度矩阵,并以之代替一致浓度矩阵,从而有效避免了有限元法计算结果的不合理性。进而通过和室内快速氯离子扩散试验结果和精确解相比较,表明了本试验方法具有很强的稳定性,且所需计算机的内存少,计算效率高,计算结果的误差随着空间和时间离散网格的加密而逐渐缩小。
Some unreasonable phenomena,such as numerical oscillations and negative value,emerge calculation result of chloride concentration in concrete when the problem of chloride diffusion is achieved by the finite element method(FEM).The lumped concentration matrix(LCM) is presented,and the unreasonable phenomena could be avoided effectively by replacing coordination concentration matrix(CCM)with LCM in finite element equation.Some examples are given to demonstrate the saving in storage space and the increase in computational efficiency with the LCM,and the relative error decrease with the refinement of the space mesh and time step for FEM based on CCM.