Time-Dependent Deformation of Concrete and Its Uncertainty

这项研究计划将导致一个改进的混凝土徐变和收缩的数学模型，它的概率方面，以及它在结构中的影响。将建立本构关系，该关系考虑了变湿度下的破裂应变软化以及收缩和热膨胀系数与应力的关系。在具有温度控制的独特的大型三轴扭转试验机中，将用六英寸圆柱体在各种潮湿条件和高温下进行蠕变试验。此外，还将测试小圆筒在三轴扭转载荷下的蠕变，其中由于湿度变化引起的断裂通过预应力来抑制。还将测量裂缝对混凝土整体干燥扩散率的影响。对逐步有限元分析的数值算法进行了阐述和数值验证，并展示了其在结构分析中的某些应用。

This research program will lead to an improved mathematical model for creep and shrinkage of concrete, its probabilistic aspects, and its effects in structures. Constitutive relation, which takes into account strain-softening due to fracturing at variable humidity and stress-dependence of shrinkage and thermal expansion coefficients, will be developed. Creep tests at various moisture conditions and high temperatures will be conducted with six-inch cylinders in a unique, large triaxial-torsional testing machine with temperature control. Also tested will be creep of small hollow cylinders under triaxial-torsional load in which fracturing due to humidity variations is suppressed by prestress. Effects of cracking on the overall drying diffusivity of concrete will also be measured. Numerical algorithms for step-by-step finite element analysis will be formulated and verified numerically, and certain applications in structural analysis will be demonstrated.