配筋率对UHPC梁抗弯承载力影响的试验研究

Experimental Study on the Effect of Reinforcement Ratio on the Flexural Capacity of UHPC Beams

为了研究配筋率对UHPC梁抗弯性能的影响,进行了18根不同配筋率的UHPC矩形梁四点弯曲试验,与2根普通钢筋混凝土(RC)试验梁进行对比,分析了破坏模式、裂缝分布、荷载-位移曲线、应变等数据.试验结果表明:与同配筋的RC梁相比,UHPC梁开裂荷载、屈服荷载和极限荷载分别提高了29%、41.5%和35.1%.随着配筋率增加,UHPC梁分别出现了少筋破坏、适筋破坏、超筋破坏三种模式,抗弯承载力随着配筋率增大而增加.将承载力试验值与现行相关规程计算值进行比较表明,规程计算值比试验值低30%~40%,因此提出了考虑受拉区UHPC抗拉作用的承载力计算公式,计算得到的配筋率界限值ρmax和极限抗弯承载力与试验值吻合较好,为UHPC梁的设计提供参考.

The four-point bending tests of the 18 ultra high performance concrete(UHPC)beams with different reinforcement ratio and the two reinforced concrete(RC)beams,were carried out to study the effect of reinforcement ratio on the flexural behavior of UHPC beams.The failure mode,crack distribution,load-displacement curve and strain were analyzed.The experimental results show that the cracking load,yield load and ultimate load of UHPC beams are increased by 29%,41.5%and 35.1%,respectively,compared with the RC beams with the same reinforcement ratio.With the increase of reinforcement ratio,UHPC beams have three failure modes such as less reinforcement failure,suitable reinforcement failure and over reinforcement failure.The flexural capacity is enhanced with the increase of reinforcement ratio.By comparing the experimental values of the bearing capacity with those calculated in the current code,the calculated values in the code are about 30%-40%lower than the experimental values.Therefore,the calculation formula of the bearing capacity considering the tensile effect of UHPC in the tensile zone is proposed in this study.The calculated threshold values of reinforcement ratioρmax and ultimate bending capacity are in good agreement with the experimental values,which can provide a reference for the design of UHPC beams.