预制UHPC组合梁槽口式连接界面抗剪性能研究

相比现浇混凝土桥面板,全预制混凝土桥面板有诸多优势,能够提高桥梁工程质量、加快桥梁施工速度和降低成本。预制超高性能混凝土(Ultra-high Performance Concrete,UHPC)梁和预制UHPC桥面板通过槽口连接形成组合梁是一种新的结构形式,这种槽口式连接的界面抗剪性能会影响全梁整体承载力。通过16个推出试件,研究不同界面抗剪钢筋配筋率、预制梁混凝土类型和预制桥面板混凝土类型、槽口填充混凝土类型对界面抗剪承载力的影响,在试验过程中观测裂缝的发展和破坏模式,记录竖向滑移、水平滑移和试件破坏模式、钢筋应变、极限荷载Vu和残余荷载Vr。试验结果表明:界面抗剪钢筋配筋率对Vu和Vr起主要作用,配筋率为3.7%的界面极限荷载分别是配筋率为2.8%和2.0%的1.06倍、1.20倍;不同的槽内填充混凝土和预制梁混凝土二者共同影响Vu和Vr;预制桥面板混凝土类型对抗剪性能影响不大;钢筋的销栓作用主要受到钢筋直径和混凝土强度等级的影响;通过与AASHTO LRFD 2015和ACI 318规范对比发现,2个规范对UHPC组合梁槽口式连接界面抗剪承载力估计保守;提出的预制UHPC组合梁槽口式连接界面抗剪计算公式计算值与试验值吻合较好。

Study on the Interface Shear Behavior of Precast UHPC Composite Beam with Shear Pocket

Compared with cast-in-place concrete bridge decks,full-depth precast concrete bridge decks have numerous advantages,which can improve the quality of precast concrete slabs,accelerate bridge construction,and reduce costs.In this study,the interface shear behavior of a novel shear pocket was evaluated,which connected a precast ultra-high performance concrete(UHPC)beam and a precast UHPC bridge deck.The interface shear behavior of shear pocket effects the overall load-bearing capacity of the composite beam.Sixteen push-out specimens with different reinforcement ratios,concrete types of precast beam,concrete types of precast deck,and grouted concrete types were tested to estimate the effect on the interface shear behavior.The propagation of cracks were observed during the test,and the vertical slip,horizontal slip,reinforcement strain,ultimate load,and residual load were recorded.The test results showed that the reinforcement ratio plays a significant role in the ultimate Vuand residual Vrloads.The ultimate load with a reinforcement ratio of 3.7%is 1.06times and 1.20times the reinforcement ratio of 2.8%and 2.0%,respectively.Second,Vuand Vrare dominated together by the grouted concrete types and precast beam concrete types.Third,the precast bridge deck concrete type has a slight effect on the shear behavior.Simultaneously,it is deduced that the dowel action of the reinforcement is mainly affected by the diameter and concrete strength grade.Compared with AASHTO LRFD 2015and ACI 318,it is inferred that the two codes are conservative in estimating the shear capacity of UHPC composite beams by shear pocket connection.Finally,a formula for predicting the precast UHPC composite beam is proposed in this paper,which is in good agreement with experimental value.