长期荷载作用下钢管混凝土徐变的理论研究

Theoretical investigation of creep in concrete filled steel tube columns under long-term load

为了解钢管混凝土在长期荷载作用下的变形特性,基于三维黏弹性理论,采用三参数线性黏弹性模型,提出了核心混凝土徐变的三维有限元分析理论和计算方法.在对两组RC梁长期加载实验研究的基础上,拟合了模型中的三个参数,并对钢管混凝土压弯构件的徐变规律进行了研究,分析中通过离散时间,采用切线模量法迭代计算得到徐变与持荷时间的关系,计算与实验结果符合较好.以典型截面形式压弯构件为例,研究了轴压比、长细比和偏心率等因素对钢管混凝土徐变的影响规律.研究结果可供工程实践和设计参考.

Based on three-dimensional (3D) viscoelastic theory, 3D finite element analytical model of core concrete creep was proposed, in which a linear three parameters viscoelastic model was adopted. This study was aimed at accurately determining the long-term effects of concrete filled steel tube (CFT) structures under eccentric load. After the evaluation of the parameters in the proposed creep model, and based on the experimental measurements of two reinforced concrete beams, the creep phenomenon of five CFT columns under long-term eccentric load was investigated. The method of tangent modulus was adopted as an approach to study the relation of creep strain and load time. In the experimental and calculating results, it could be found that they have a good agreement. The CFT columns with representative geometry and sectional dimensions were taken as examples and the proposed method was used as an approach to investigate the influencing regularities of many factors, which included the ratio of long-term load to strength, the slenderness ratio, and the eccentricity ratio, on CFT structures.