预应力UHPC槽形节段与整体式混凝土板组合梁受剪性能

Shear behavior of composite girder with prestressed UHPC channel segments and monolithic concrete slab

将预制的UHPC槽形节段通过干缝连接和预应力张拉形成槽形梁,再与整体现浇的混凝土板组合成的组合梁,称为预应力UHPC槽形节段与整体式混凝土板组合梁(PUCS-MCS组合梁)。它是一种能充分发挥不同材料的性能、施工方便且整体性能好的新型桥梁结构。为探究其抗剪性能,开展了9根模型梁的试验。分析了接缝数、接缝处剪力键数、剪跨比、UHPC钢纤维体积率、配箍率和纵筋率等参数对试件变形、破坏模式、抗剪承载力的影响;基于试验研究结果,提出了PUCS-MCS组合梁抗剪承载力计算方法。结果表明:PUCS-MCS组合梁均为剪压破坏,所有梁在开裂前的荷载-挠度曲线差异不大,在开裂后刚度不断下降;PUCS-MCS组合梁的抗剪承载力随接缝处剪力键数、UHPC钢纤维掺量、配箍率和纵筋率的增大而增大,随干接缝数量增加和剪跨比的增大而减小,其中影响最显著的是干接缝和剪力键,影响最小的是钢纤维掺量和配箍率,因此PUCS-MCS组合梁可不配箍筋,并可采用较低钢纤维掺量的UHPC。

Prefabricated ultra-high performance concrete(UHPC)channel segments are connected by dry joints and prestressed tension to form a channel girder,which is then combined with a cast-in-place concrete slab to form a composite girder,which is called as prestressed UHPC composite segments girder with monolithic concrete slab(PUCS-MCS composite girder).It is a new type of bridge structure that can fully utilize the performance of different materials,provide good overall performance,and is easy to be constructed.To explore its shear behavior,experimental study was conducted on the shear behavior of nine specimens with the parameters of dry joint number,number of the shear keys in the joint,shear-to-span ratio,steel fiber volume fraction of UHPC,stirrup ratio,and longitudinal reinforcement ratio.The effects of each parameter on the deflection,failure mode,and shear capacity of the specimens were analyzed.Based on the experimental study results,a formula was proposed for predicting the shear capacity of PUCS-MCS composite girder.The results show that the PUCS-MCS composite girders are all failed in shear compression.The load-deflection curves of all specimens are similar before cracking,and the stiffness of the PUCS-MCS composite girders weaken more significantly than that of monolithic girder without joint after cracking.The shear capacity of PUCS-MCS composite girders increases with the number of the shear keys in the joint,the steel fiber volume fraction of UHPC,the stirrup ratio,and longitudinal reinforcement ratio,and decreases with the dry joint number and shear-to-span ratio.Among these parameters,the most significant effects are induced by the number of shear keys and dry joints,and the least are the steel fiber volume fraction and the stirrup rate.Therefore,a PUCS-MCS composite girder can be made without stirrup,and the UHPC can be mixed with low steel fiber volume fraction.