大尺寸钢筋混凝土梁收缩试验研究

Experimental Study on Shrinkage of Large-Sized Reinforced Concrete Beam

针对目前钢筋混凝土梁收缩试验研究较欠缺,相应公式未得到验证的问题,设计了2根大尺寸钢筋混凝土梁收缩试件,测试了2 d和4 d龄期钢筋处的收缩应变,分析了既有钢筋混凝土柱和梁收缩公式的差异性,并与试验结果进行了对比。结果表明:受钢筋约束影响,钢筋内会存在12.6 MPa的压应力;混凝土徐变会降低34%的收缩应力;受拉和受压侧钢筋配筋率和重心距中性轴距离差别越大,钢筋混凝土梁拉、压侧钢筋收缩应变差越大;对此类钢筋混凝土梁设计时,考虑受压和受拉区不同配筋形式的钢筋混凝土梁收缩公式的计算结果较其他公式结果小,且与试验吻合较好,需考虑收缩应变引起的曲率和应力重分布效应。研究成果可为准确预测钢筋混凝土梁的长期变形和钢筋应力提供参考。

Because of the lack of research on shrinkage experiments of reinforced concrete beams and unverified corresponding formulas,this paper designs two pieces of shrinkage specimens of the large-sized reinforced concrete beam to measure the shrinkage strain of the reinforcement at ages of 2 days and 4 days.The difference in shrinkage formula between the existing reinforced concrete column and beam is analyzed and compared with the experiment result.The results show that there is compressive stress of 12.6 MPa in the reinforcement due to the constraint and the concrete creep would reduce the shrinkage stress by 34%.The greater the difference between the reinforcement ratio and the distance between the center of gravity and the neutral axis,the greater the shrinkage strain difference between the tensile and compressive sides of the reinforced concrete beam.During the design of this type of reinforced concrete beam,the calculation result of the shrinkage formula considering different reinforcement forms at the compression and tension zones is smaller than that of other formulas and in good agreement with the experiment result,and the curvature and stress redistribution effects caused by the shrinkage strain should be considered.The study results can provide a reference for accurately predicting the reinforced concrete beam’s long-term deformation and reinforcement stress.