门式刚架轻钢结构抗风安全性分析

Wind-resistant safety analysis of light-weight steel portal frame structures

为研究门式刚架轻钢结构的抗风安全性,采用风洞试验方法对我国东南沿海一轻钢厂房的表面风压进行了测试;将测得的2个最不利风向的风荷载以及按荷载规范和轻钢规程计算的风荷载分别施加于厂房的不利刚架上,采用基于板壳单元的精细有限元方法对刚架进行极限承载力的非线性分析,获得了在不同工况下刚架的抗风安全系数和风致破坏形态.通过对刚架在不同风荷载取值下的风致安全性进行了对比分析,结果显示:该刚架在轻钢规程的风荷载以及由风洞试验得到的极端风荷载作用下的安全冗余度偏低;而直接按荷载规范的风荷载(未含阵风系数)进行抗风设计可能会使承重刚架偏于不安全;通过一种简便的节点构造改进措施,可以明显提高刚架的风致安全性,并降低刚架对初始缺陷的敏感性.

In order to investigate the wind-resistant safety conditions of light-weight steel portal frame structures,the wind pressures on the surface of a light-weight steel industrial building located at the southeast coastal area of China were measured by means of the wind-tunnel test technique.The wind loads under two most unfavorable wind directions obtained from the measured data and the loads determined from the load code for building structures and the technical specification for steel gable frame structures were applied to the unfavorable frame of the building.The nonlinear load-capacity analyses were then performed using the refined plate/shell element based finite element method,and the wind-resistant safety factors and ultimate-state failure modes of the frame were thereafter found.Analysis and comparison of the obtained wind-resistant safety factors under different load cases,indicate that the degrees of safety redundancy of the frame in consideration under the wind load determined from the steel gable frame specification and the extreme wind load from the wind tunnel test are relatively low,and the wind resistant design in accordance with the load code wind loading（no gust factor included）would probably lead the frame to an unsafe condition.A simple and effective beam-column connection enhancement measure is proposed thereafter,by which the safety level of the frame could be considerably improved and the sensibility to initial imperfections could be reduced.