钢筋混凝土框架柱和轻钢拱结构失效方程复杂特性与设计可靠度

Complex failure function and design reliability for RC frame columns and light-weight steel structures

以全跨永久荷载和半跨雪荷载组合作用下的轻钢拱结构与重力荷载和水平地震组合作用下的钢筋混凝土框架柱两类典型情形为研究对象,采用现行相关设计规范中的承载力计算式推导其失效方程。采用相应结构实例对两类典型情形下的失效方程复杂特性进行分析,表明轻钢拱结构具有较大的雪荷载效应比值和钢筋混凝土大偏压柱失效方程具有较高程度非线性。考虑以上特性,对两类典型情形进行可靠度校准分析,结果表明:雪荷载组合作用下轻钢拱结构的可靠度较低,建议雪荷载分项系数值取为1.75;钢筋混凝土框架柱在不同抗震承载力设计情形下其失效概率会有较大的差异,且无法通过将柱端弯矩增大系数简单增大到某一值而消除,同时在轴压力荷载效应比值为负的情形下现行设计方法会偏于不安全。

Based on the capacity formulas in design codes, the corresponding failure functions are obtained for two typical cases, which are the light-weight steel arch structures under combined full-span dead load and half-span snow load and reinforced concrete （RC） frame columns under combined gravity load and horizontal earthquake action. Then, the complex characteristics of failure function were analyzed through multiple examples. It indicates that the snow load effect ratio is large for light-weight steel arch structure and the failure function is highly nonlinear for RC column with large eccentric compression. Furthermore, the reliability level was calibrated for these two typical cases. The results show that a more conservative design is needed for the light-weight steel arch structure under snow load combination due to its low reliability level; and the differences of failure probability of RC frame columns are large under different cases of seismic capacity design, and such differences are not able to be eliminated by a strategy that simply makes the strong column coefficient increase to a certain value, and an unsafe design of seismic capacity may be given by the current method, when the load effect ratio based on axial compressive force is negative.