配置HRBF500钢筋的无粘结预应力梁受弯性能试验研究

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〈450MPa时,该式的计算值与试验值符合较好。

Experimental Analysis on Bending Capacity of Unbonded Prestressed Concrete Beams with HRBF500 Steel Bars

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.