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非常复杂，有许多问题需要弄清楚。众所周知，冲切强度随着加载位置接近构件的自由边而减小，然而，有关这种性能的试验数据不足以应用于各种类型的构件的设计。此外，在剪跨较短的情况下，抗剪钢筋的有效性仍然不确定。在本研究中，钢筋混凝土板和深梁试件进行了试验。板试验的变量包括荷载到自由边的距离、荷载位置的深度(表面荷载和埋入荷载)、主筋和配筋的布置、板的宽度和箍筋的存在；深梁试验的变量有剪跨比、剪筋类型、水平筋、组合箍筋和水平筋的数量。主要结果如下：1)在受拉平面构件的设计中，可以方便地将破坏机制分为五种类型；梁的全宽剪切、梁的有效宽度剪切、临界截面全长的冲切、临界截面有效长度的冲剪和素混凝土的剪切。2)在短剪跨度情况下，箍筋的影响可能小于桁架理论的估计值。可以引入作为剪跨比和剪力配筋度的函数的折减系数。

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.