Pull-out Shear Strength of Planar Reinforced Concrete Members

钢筋混凝土构件在拉拔力作用下的破坏机理十分复杂，有许多问题有待阐明。众所周知，当荷载位置接近构件自由边缘时，冲孔抗剪强度降低，但有关这种行为的试验数据不足以应用于各种构件的设计。此外，在短剪跨的情况下，抗剪加固的有效性仍然不确定。本研究对钢筋混凝土板和深梁试件进行了试验。板坯试验研究的变量是荷载到自由边的距离、荷载位置深度（表面荷载和预埋荷载）、主筋和配筋的布置、板坯宽度和箍筋的存在；深梁试验研究的变量是剪切跨深比、剪力筋类型、箍筋、箍筋组合、箍筋组合和箍筋数量。得到的主要结果如下：1)在平面构件受拉出力的设计中，方便地将其分为五种破坏机制；全宽梁剪、有效宽度梁剪、临界截面全长冲剪、临界截面有效长度冲剪、素面混凝土剪切。2)在剪跨较短的情况下，马镫的作用可能小于桁架理论估计的值。可以引入折减系数作为抗剪跨比和抗剪配筋程度的函数。

A mechanism of failure of reinforced concrete members subjected to pull-out forces is extremely complicated and there are many problems to be made clear. It is known that the punching shear strength decreases as a loading position approaches the free edge of a member, however, the test data concerning such behavior are not enough to be applied to the design of various kinds of members. Furthermore, the effectiveness of shear reinforcement in the case of short shear span still remains uncertain.In this study reinforced concrete slab and deep beam specimens were tested. The variables investigated in the slab tests were distance from load to free edge, depth of loading position ( surface loading and embedded loading), arrangement of main and distribution reinforcements, slab width and presence of stirrups, and those in the deep beam tests were shear span-to-depth ratio, type of shear reinforcement stirrups, horizontal bars, combined stirrups and horizontal bars ) and amount of shear reinforcement.The principal results obtained are as follows; 1) In the design of planar members subjected to pull-out forces it is convenient to classify into five types of failure mechanism; beam shear with full width, beam shear with effective width, punching shear with full length of critical section, punching shear with effective length of critical section and shear of plain concrete. 2) The effect of stirrups in the case of short shear span may be less than the value estimated by the truss theory. Reduction factor as a function of shear span ratio and degree of shear reinforcement may be introduced.