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STUDIES ON THE EFFECTS OF ENVIRONMENTAL CONDITION ON LONG-TERM DEFORMATION AND CRACK WIDTH OF REINFORCED CONCRETE MEMBERS

环境条件对钢筋混凝土构件长期变形及裂缝宽度影响的研究

基本信息

批准号：
03650389
负责人：
SATO Ryoichi
金额：
$ 1.28万
依托单位：
UTSUNOMIYA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

Deformational and cracking behaviors of reinforced concrete beams subjected to sustained flexural load were experimentally investigated under four different environmental conditions, that is, (1) in the room with the temperature of 20(]SY.+-。[)1ﾟC and relative humidity of 60(]SY.+-。[)5%, (2) in that with 70(]SY.+-。[)5%, (3) in the laborato-ry and (4) in the feild. Furthermore, computations of time-dependent deformations and crack widths of reinforced concrete flexural member under alternating temperature and humidity were performed, using numerical method developed by authors. Main results were abtained as follows ;(1) Creep was promoted mainly by seasonal temperature rise and did not necessarily depend upon relative humidity. Drying shrinkage strain in the feild, which changed reversibly during exposure to water, resulted in nearly a half of that in the laboratory due to rainfall.(2) Both curvature and compressive strain depended closely on creep and drying shrinkage. Curvatures and compressive strains of beams with compressive reinforcement were underestimated especially in the field by analysis used effective elastic modulus method. A step-by-step method based on Whitney's rate of creep law was effective in improving the procedure in terms of accuracy to a certain extent.(3) Effective rate of drying shrinkage to increase of crack width under load in the field was larger than that in the laboratory. This means that cracks do not necessarily widen in proportion to the magnitude of drying shrinkage strain.

试验研究了四种不同环境条件下钢筋混凝土梁在持续受弯荷载作用下的变形和开裂行为，即(1)温度为20(]SY.+-的室内。[)1 . <s:1> <s:1> <s:1>温度，相对湿度60（]±±）。[)5%,(2)在70(]SY.+-。[)5%,(3)在实验室和(4)在现场。在此基础上，采用自行开发的数值计算方法，计算了钢筋混凝土受弯构件在温湿交变条件下的变形和裂缝宽度随时间的变化。主要结果如下：(1)蠕变主要受季节增温的影响，相对湿度对蠕变的影响不大。田间干缩应变在水分作用下发生可逆变化，其结果是降雨作用下实验室干缩应变的近一半。(2)曲率和压缩应变与蠕变和干缩密切相关。采用有效弹性模量法进行分析时，尤其在现场低估了受压配筋梁的曲率和压应变。基于惠特尼蠕变速率定律的分步法在一定程度上提高了计算精度。(3)在荷载作用下，现场干燥收缩对裂缝宽度增大的有效率大于实验室。这意味着裂缝的扩大不一定与干燥收缩应变的大小成比例。