循环荷载作用下钢梁临界侧向长细比研究

针对我国《建筑抗震设计规范》推荐的临界侧向长细比计算公式来源于单调荷载研究结果,并未反映不同抗震等级影响问题,基于抗震等级应与适宜的转动能力相匹配准则,对循环荷载作用下钢梁进行非线性有限元分析。所建模型考虑初始几何缺陷、残余应力影响,并得到试验验证。通过对钢梁端部弯矩比、腹板高厚比、翼缘宽厚比、残余应力分布图式及平面外边界约束条件等5类影响因素数值分析,提出循环荷载作用下钢梁临界侧向长细比计算公式。该公式具有计算精度高、表达形式简单等特点。

Critical lateral slenderness ratio of steel beams subjected to cyclic loading

In seismic design of steel beams, it is necessary to set lateral supports in order to diminish lateral slenderness ratio which can prevent lateral instability and can maintain sufficient rotation capacity to dissipate input energy of earthquake. The behavior of steel beams under cyclic loading is quite different from that under monotonic loading. However, the formula for critical lateral slenderness ratio recommended in the current Chinese code GB50011-2010 for seismic design of buildings is resulted from research findings for monotonic loading. At the same time, the effect of different seismic grades is not considered in the formula. So it is necessary to improve the formula. In this paper, nonlinear finite element analysis of steel beams subjected to cyclic loading is carried out based on the concept that a seismic grade should match a suitable rotation capacity. The modeling developed takes into account the influence of initial geometric imperfection and residual stresses and is validated by other researcher’s experimental results. By means of the numerical analysis for five parameters such as end-moment ratio, web height-thickness ratio, flange width-thickness ratio, residual stress distribution pattern, out-of-plane boundary condition, the formula for critical lateral slenderness ratio for the steel beam under cyclic loading is proposed, which has higher accuracy and simpler form.