考虑剪力滞后的组合梁极限承载力计算

Moment Resistance of Composite Beam at Ultimate Limit State Considering Shear-Lag Effect

根据规范中组合梁截面在正弯矩作用下塑性极限承载力计算方法,提出新的塑性阶段有效宽度定义,根据混凝土翼缘中合力和合力作用点同时等效来计算有效宽度。采用试验研究和非线性有限元方法,分析简支组合梁在极限状态下跨中截面混凝土翼缘内应变和应力分布规律,给出简化表达公式。针对各种参数情况下的组合梁,计算塑性极限阶段混凝土翼缘有效宽度和矩形应力块高度,根据简化的取值结果,提出塑性承载力的计算方法。

The effective width is usually induced in practical design due to shear lag effect in concrete slab of composite beam. In this paper, a new concept of effective width of composite beam under sagging moment at ultimate limit state is introduced. The effective width was calculated based on the equivalent of the resultant force and the acting location in concrete flange. Simply supported composite beams were analyzed by means of experimental study and nonlinear finite element method. The strains and stresses distribution across mid-span section of concrete flange were investigated and expressed by simplified formulae. The effective width of concrete slab and depth of rectangular tress block at ultimate limit state were calculated under usual beam proportions. Simplified formulae were proposed for effective width at plastic ultimate limit state.