T形配筋应变强化UHPC梁弯曲破坏机理

为分析应变强化UHPC梁弯曲破坏时UHPC和钢筋应变间关系,对5根梁试件进行了三分点加荷纯弯试验,试件变化参数为配筋率和钢筋种类.绘制了钢筋与应变强化UHPC的荷载-挠度曲线,将T形梁破坏过程分成3个阶段:弹性阶段、裂缝发展阶段、持荷至破坏阶段进行分析.并绘制了钢筋与应变强化UHPC的荷载-应变曲线,深入分析了在整个受弯过程中钢筋与UHPC的协同工作性.同时,结合UHPC和钢筋的应力-应变关系,将加载过程分为4个阶段,定量分析每个阶段钢筋和UHPC对抗弯承载力的贡献度.结果表明:钢筋达到屈服应变之前,钢筋与UHPC粘结可靠,保持应变一致性而共同受力;整个受弯过程中,应变强化UHPC抗拉强度提供的抗力与钢筋提供的相比占据重要比例(低配筋率时更大),建议在进行应变强化UHPC截面承载力计算时,应充分考虑UHPC抗拉强度的作用,保证承载能力计算方法的准确性.

Flexural failure mechanisms of rebar-reinforced high strain-hardening UHPC T-beams

To investigate the relationship of strain between the high strain-hardening UHPC and the reinforcement when the flexural failure of beams occurred, one-third loading experiments were carried out on five girder specimens. During the tests, the change parameters of the specimens are the reinforcement percentage and the type of reinforcement. Firstly, the load-deflection curves of reinforcement and high strain strengthening UHPC indicate that T-beam failure process could be divided into three stages: the elastic stage, the fracture development stage and the load-to-failure stage. Secondly, the cooperation between reinforcement and UHPC was discussed based on the load-strain curves of reinforcement and high strain-strengthening UHPC. Finally, the loading process was divided into four stages according to the stress-strain curves of reinforcement and high strain-strengthening UHPC. The results show that the reinforcement rebar and the UHPC present reliable cohesiveness and could keep the strain consistent before the reinforcement reaches the yield strain. The resistance of high strain-hardening UHPC tensile strength plays more important proportion than reinforcement rebar during the flexural process, and it could be bigger at a low percentage of reinforcement. It is suggested that the tensile strength of UHPC should be taken into account when calculating the bearing capacity of high strain-hardening UHPC, and ensure the accuracy of the calculation method of bearing capacity.