梁端削弱形式对火灾下钢框架抗连续倒塌性能影响

为探究不同梁端削弱形式对火灾下钢框架结构抗连续倒塌性能影响,对中柱失效2层2跨钢框架梁-柱子结构进行常温下Pushdown加载试验,研究其竖向抗力曲线和破坏模态。试验结果表明：中柱失效钢框架结构主要依靠弯曲机制和悬链线机制抵抗外加荷载,且悬链线机制具有滞后性。随后在试验的基础上,通过ABAQUS建立二层平面钢框架模型,并对其展开常温下和火灾下的拟静力模拟,对出现的削弱型梁翼缘、二次削弱型梁翼缘、开洞梁腹板和开洞梁翼缘四种梁端削弱方式进行抗连续倒塌分析。有限元结果表明：削弱型梁翼缘和二次削弱型梁翼缘不论在常温还是高温下,都能提供比未削弱情况下的模型更高的结构竖向抗力和变形能力。较于其他梁端削弱形式,考虑悬链线效应,二次削弱型梁翼缘变形能力最好。

Behavior of progressive collapse of steel frame under fire with different reduced beam section connections

To explore the influence of different reduced beam section connections on progressive collapse resistance of steel frame structure under fire, first of all, pushdown methods of two-story two-span steel frame beam-column substructure with middle column failure under normal temperature were carried out, and the resistance curves and failure modes in the collapse process were studied. The test results show that the middle column failure steel frame structure mainly relies on the bending mechanism and the catenary mechanism to resist the external load, and the catenary mechanism has hysteresis. Then, on the basis of the test, the two-story plane steel frame model was established by ABAQUS, and the quasi-static simulation at room temperature and fire was carried out. The progressive collapse resistance analysis was carried out on the four beam reduced section connections of RBS (reduced beam section), DRBS (double reduced beam section), OBW (opening beam web) and OBF-2 (opening beam flange). The FEM (finite element model) results show that RBS and DRBS can provide higher vertical resistance and deformation capacity than the unreduced model at both room temperature and high temperature. Compared with other reduced beam section connections, DRBS has the best deformation ability considering catenary effect.