剪弯混凝土梁直断缝处的承载力分析

Analysis of bearing capacity on straight fracture of shear bending concrete beam

对于常规配筋并受剪弯作用的钢筋混凝土梁,考察其相邻箍筋间距内的梁段(无箍筋梁段)受拉区出现一定长度的竖直断缝,该断缝处,所有剪力均由纵向钢筋和未断开混凝土组成的组合截面抵抗(该梁段外的箍筋使纵向钢筋和混凝土箍成整体,并给纵筋传递剪力),此时纵向钢筋必然受剪,但现行规范对钢筋剪力并无考察及规定。在断缝处,钢筋屈服将可能受到钢筋剪力的较大影响。从理论上给出了考虑钢筋受剪拉、剪压影响时,断缝处钢筋混凝土梁剪弯承载力的计算、箍筋的拉力和剪力计算、横向或纵向直剪破坏的判别,以期提供更为严密的逻辑基础。该方法,不仅限于梁,对其余类型的钢筋混凝土构件可依此类推,并给装配式或改造建筑的后植构件断缝处的承载力分析提供参考。

For the reinforced concrete beams with conventional disposed rebar and shear bending load, investigate the beam section within the interval between adjacent hooping(referred to as the no hooping beam section),and the tensile area of this section have a certain length of straight fracture, at this place of straight fracture all the shear forces are resisted by the composite section composed of longitudinal rebar and intact concrete(the hoopings outside the beam section make the longitudinal rebar and concrete hooped as a whole, and transfer the shear force to the longitudinal rebar),at this time, the longitudinal rebar must be shearing, However, the current code does not inspect and stipulate the shear force of steel bars. At the place of straight fracture, the yield of steel bars may be greatly affected by shear. In this paper,the calculation of shear bending capacity at the straight fracture place of reinforced concrete beams, the calculation of tension and shear force of hoopings, and the judgment of transverse and longitudinal direct shear failure are given in theory when considering the influence of shear tension and shear pressure on rebar, in order to provide a more rigorous logical basis. The method shown in this paper is not only limited to beams, but also for other types of reinforced concrete members, it also provides a reference for the analysis of bearing capacity at the fracture of fabricated members and planting components of reconstruction.