实配钢筋“强剪弱弯”型RC框架梁可靠度分析

Reliability analysis of the "strong shear weak bending" real reinforced RC frame beam

防止框架梁剪切破坏是框架结构抗连续倒塌设计的基本要求。研究表明,框架梁抗剪能力不足是导致框架结构"强柱弱梁"耗能机制难以形成的重要因素之一。这就需要在设法保证框架接近形成梁铰型塑性机构的同时,防止梁端塑性铰区在其达到塑性变形状态之前发生脆性剪切破坏,即通常所说的RC框架梁"强剪弱弯"措施。建立框架结构梁端实配钢筋"强剪弱弯"可靠度极限状态方程,利用一次二阶矩实用分析法求解梁端可靠度。设定框架梁"强剪弱弯"目标可靠度βt:一级抗震等级βt=3.1,二级抗震等级βt=2.6,三级抗震等级βt=2.1,四级抗震等级βt=1.6。根据6组不同抗震设防烈度钢筋混凝土框架结构实配钢筋施工图,求出梁端节点可靠度β,对不符合"强剪弱弯"可靠度要求的梁端,采取增大箍筋配筋面积和改变梁截面尺寸的方法,确保框架结构梁端满足"强剪弱弯"可靠度水平。

To prevent the progressive collapse of frame beam shear failure is the basic requirements of the design for frame structures mechanism. Research shows that the beam shear capacity is one of the important factors causing the ' strong column weak beam' energy dissipation mechanism is difficult to form a frame structure. This needs to ensure that close to the frame type plastic hinge beam forming mechanism at the same time,to prevent the beam end plastic hinge in to brittle shear plastic deformation occurs before the destruction of the state,namely the RC frame beam usually said ' strong shear weak bending' measures. The frame beam end reinforced ' strong shear weak bending' reliability limit state equation is established and the analysis method is used to solve the beam end reliability using the first-order second moment. Setting frame beam ' strong shear weak bending' target reliability βt: first grade anti earthquake grade βt= 3. 1,two grade anti earthquake grade beta βt= 2. 6,three grade anti earthquake grade beta βt= 2. 1,four grade anti earthquake grade βt=1. 6. According to 6 groups of different seismic fortification intensity of reinforced concrete frame structure with steel construction graph and calculate the beam end node reliability beta,does not conform to the ' strong shear weak bending' reliable degree requirements of the beam end,take increasing stirrup area and change the dimensions of the cross-section of the beam method,ensure that the frame beam end meet ' strong shear weak bending' reliability level.