混凝土材料非线性多轴动态强度准则

将广义非线性强度理论的4个材料参数转化为混凝土材料的基本强度参数,通过混凝土材料的基本强度特性,分析了4个材料参数的变化规律与取值范围.基于S准则建立了混凝土材料4个基本强度参数的率效应表达式,建立了混凝土材料的非线性多轴动态强度准则,分析了动态强度参数的率效应规律,结果表明,混凝土材料的强度特性随着应变率的提高,逐渐向金属材料的强度特性过渡,在应变率从-3~3,应变率对混凝土动态强度的影响较大,并且动强度不是随着应变率的提高无限增大的,而是存在动强度峰值.通过与3组双轴压-压和2组双轴拉-压动态加载时混凝土材料试验结果的比较,表明非线性多轴动态强度准则可较好地描述混凝土材料双轴动强度规律.在同一应变率下,可较好地描述强度的非线性特性;不同应变率下,动强度面互不相交,即应变率效应与多轴应力状态对强度规律不存在耦合影响.

Nonlinear multiaxial dynamic strength criterion for concrete material

Basic strength parameters of concrete material which are uniaxial compressive strength, uniaxial tensile strength, biaxial compressive strength and biaxial tensile strength are used to replace the four material parameters of generalized nonlinear strength theory in this study. The change rules and value ranges of four material parameters are acquired by studying the basic strength characteristics of concrete materials. Nonlinear multiaxial dynamic strength criterion for concrete material is proposed by four rate effect expressions of basic strength parameters for concrete material, and the four rate effect expressions are established on the basis of S criterion. The rate effect rules of dynamic strength parameters express that with the increase of strain rate, strength properties of concrete gradually transform to that of metal material. Dynamic strength of concrete is significantly influenced by the strain rate in the range of -3 to 3, and dynamic strength does not increase indefinitely, instead, there is a peak dynamic strength. Compared with dynamic loading test of biaxial compressive-compressive and biaxial tensile-compressive of concrete, nonlinear multiaxial dynamic strength criterion can describe the biaxial dynamic strength rule of concrete reasonably and the nonlinear strength characteristics at a certain strain rate. Strength rules are not influenced by coupling between the strain rate effect and multiaxial stress state, in other words, the dynamic strength surfaces dose not intersect at different strain rates.