配置HRBF500钢筋的无粘结预应力梁受弯性能试验研究:无粘结预应力钢筋
摘 要：进行了10根简支梁的受弯性能试验，研究了以HRBF500钢筋作为纵向受拉钢筋的无粘结预应力混凝土梁的破坏特征、预应力增量、受弯承载力以及位移延性。试验研究表明：在达到极限状态之前，试验梁中受拉的HRBF500钢筋均已屈服；梁破坏时，受压区混凝土压碎，破坏较为突然；无粘结预应力筋的实测极限预应力增量与综合配筋指标仍基本成线性关系，但较规范GB 50010－2010中公式的计算值明显偏大，计算值与试验值比值平均为0.35；梁跨中的屈服位移较大，但位移延性较差，位移延性系数平均为1.67，且随综合配筋指标增大，位移延性系数减小。根据笔者及相关文献中的试验结果，分析得到了无粘结预应力筋的极限预应力增量计算的建议公式，当极限预应力增量试验值<450 MPa时，该式的计算值与试验值符合较好。
关键词：预应力混凝土；无粘结预应力；预应力增量；受弯承载力；延性
中图分类号：TU375.1;TU378.2
文献标志码：A
文章编号：1674-4764（2012）04-0031-07
Experimental Analysis on Bending Capacity of Unbonded Prestressed Concrete Beams with HRBF500 Steel Bars
ZHENG Yimina, HE Lidongb, ZHAO Yongb
(a. Architectural Design & Research Institute (Group) Co. Ltd;
b. Department of Building Engineering, Tongji University, Shanghai 200092, P. R. China)
Abstract:The bending capacity tests on ten simple supported beams were conducted to investigate the damage characteristics, prestress increment, beading capacity and displacement ductility of unbounded prestressed concrete beams with HRBF500 steel bars. The results show that the HRBF500 steel bars has yielded before the limit state. The concrete in compression zone crushes upon the broken of the beams, which shows a sudden damage mode. The measured ultimate stress increments of unbounded tendons are in linear relationship with the comprehensive reinforcement ratio index, while the values of the ultimate stress increments are obviously higher than those values specified in the code GB50010-2010, and the average ratio of predicted values to testing values is about 0.35. The mid-span deflection upon yielding of the beams is large, while the displacement ductility is bad and the average value of the displacement ductility ratio is 1.67. The displacement ductility ratio decreases with the increases of the comprehensive reinforcement ratio index. Based on the experimental results, the proposed calculation formula of ultimate stress increments of unbounded tendons was established, and it is in good agreement with the experimental results when the testing value is less than 450 MPa.
Key words:prestressed concrete; unbonded prestress; prestress increment; bending capacity; ductility
采用500 MPa级钢筋代替335或400 MPa级钢筋作为混凝土梁的受拉纵筋后，在同样的受弯承载力要求下，一般可以减少钢筋的用量，具有较好的效益，值得推广应用。在新版中国国家标准《混凝土结构设计规范》［1］(GB 50010－2010)中已将HRB500和HRBF500钢筋纳入，而且已有的试验研究结果表明［2-4］，规范GB 50010－2010的正截面受弯承载力计算公式适用于配置500 MPa级钢筋的非预应力混凝土梁。由于规范GB 50010－2010中无粘结预应力梁的受弯承载力计算模式主要源自行业标准《无粘结预应力混凝土结构技术规程》［5］(JGJ 92－2004)，且是建立在配置335 MPa级钢筋的梁、板受弯性能试验结果的基础上的，是否仍适用于配置500 MPa级钢筋的无粘结预应力梁值得商榷。