玻璃纤维增强复合材料弯折筋增强超高性能混凝土拉拔试验及受力模型研究

Research on Pull-out Test and Stress Model of UHPC Reinforced with GFRP Bent Bars

通过玻璃纤维增强复合材料(GFRP)弯折筋增强超高性能混凝土(UHPC)拉拔试验,研究了GFRP筋弯折区域力学服役性能及损伤机制,揭示了GFRP弯折筋与UHPC协同受力状态,建立了试件受力模型。试验研究变量包括:GFRP筋材直径、弯折筋尾部锚固长度、筋材尾部形状以及筋材基体种类。研究表明,受到GFRP筋材弯折区域褶皱和受力肩应力集中影响,GFRP筋材直径对弯折强度影响较大;弯折筋尾部锚固长度的增加,在一定程度上利于GFPR筋弯折强度提升;筋材尾部形状(L型和U型)对弯折强度的影响较小。基于此,阐述了GFRP筋弯折区在受拉状态下的损伤破坏机理;提出了GFRP弯折筋三阶段断裂过程:筋材受力肩内侧基体开裂、内侧纤维断裂和外侧纤维断裂;建立了GFRP弯折筋-UHPC弯折区域拉拔状态下的受力分析模型。

Through the pull-out test of Glass Fiber Reinforced Polymer(GFRP)bent bars reinforced Ultra High Performance Concrete(UHPC),the mechanical performance and damage mechanism of GFRP bars in bending zone were studied.The cooperative performance of GFRP bent bars and UHPC was revealed.The stress model of specimens was established.The study variables include:diameter of GFRP bars,anchoring length of the tail end of bent bars,shapes of the tail ends of bars and types of bar matrix.The results showed that the diameter of GFRP bars had a great influence on the bending strength due to the influence of the fold in the bending area and the stress concentration on the shoulder.The increase of the anchoring length at the tail of the GFRP bars had an positive effect on the bending strength of GFPR bars within a certain range,while the shape of tail end(L-shaped and U-shaped)bars had a little influence on the bending strength.The failure mechanism of GFRP bars under tension in the bending zone was presented,and three stages of fracture process of GFRP bars were revealed:the matrix cracking at the inside of stressed shoulders of bars,the inner fiber cracking and the outer fiber cracking.A stress analysis model was established for the bending area of GFRP-UHPC in the pull-out state.