轻钢门式刚架风致极限承载力的非线性分析

Nonlinear analysis of wind-induced ultimate bearing capacities of light-weight steel portal frames

为研究按现有规范设计建造的轻钢门式刚架工业厂房的风致极限承载力与风致安全性问题,以浙江沿海某既有双坡屋面轻钢厂房为例,分别按风洞模型试验数据、我国建筑结构荷载规范、门式刚架轻型房屋钢结构技术规程和美国ASCE 7-05标准取用风荷载,采用精细的板壳有限元方法对厂房中的不利刚架进行了考虑弹塑性和大变形的非线性极限分析,获得了刚架在不同工况下的抗风承载力冗余系数和达到极限状态时的风致破坏模式。结果表明,该刚架虽满足风洞试验和我国相关规范风荷载的抗风承载力要求,但考虑初始缺陷时的抗风安全冗余度偏低,若对比美国标准则不满足其抗风要求;当存在初始缺陷时,刚架的破坏模式呈现迎风梁柱节点处的局部屈曲模式,而完善刚架则表现为同一节点处的材料屈服模式。

In order to investigate the wind-induced ultimate bearing capacities and wind-resistance levels of light-weight steel portal frame of industrial buildings designed and constructed under the a- vailable design codes, a gable roofed industrial building located at the southeastern coastal area of China was taken as an example, and nonlinear ultimate analyses were carried out for the unfavorable frame of the building using the refined shell element-based finite element method with consideration of elastic-plastic and large deformation properties. In the analyses, different wind load cases were considered, and the loads were determined by wind-tunnel model test, Chinese load code for the de- sign of building structures, Chinese technical specification for steel structure of light-weight build- ings with gabled frames and American Society of Civil Engineers （ASCE） standard 7-05, respec- tively. The wind-resistance redundant factors and the ultimate limit-state failure modes were then found for each above-mentioned load case. The obtained results indicate that although the frame in consideration satisfies the wind-resistance requirements under the loads determined from the wind- tunnel test and the Chinese code or specification, when considering initial imperfections, the wind- resistance safety is relatively low, and the frame cannot satisfy the requirement of ASCE 7-05 stand- ard. The results also show that frames having initial imperfections fail in the mode of local buckling at the windward beam-column connection, while frames without initial imperfection fail in the mode of material yielding at the same connection.