Beam-to-column connection configurations, such as welded, bolted, and mixed welded-bolted connections, play an important role in structural resistance and ductility under middle column-removal scenarios. This paper illustrates full-scale laboratory tests of two steel frame assemblies with different connection details under the progressive collapse scenario. One specimen adopts the modified conventional technique which has reinforced welded flange-bolted web connection (SC-WR), and the other specimen uses a slotted-hole connection based on the former (SC-WB). The failure modes, load transfer mechanism, and vertical resistance are analyzed in the test. Both connection configurations exhibit satisfactory load resistance and ductility supply. Specimen SC-WB shows the higher ultimate vertical capacity and greater chord rotation at later catenary stage due to a sufficient redistribution of the stress with the modified bolted shear tab. Moreover, finite element models (FEM) are developed and validated against the test data. FEM can accurately simulate the mechanical behaviors and the failure of specimens, which can provide an effective reference for the beam-to-column connection configurations in similar working conditions. Finally, a simplified mechanical model is exhibited in accordance with the experimental and numerical results to reveal the effect of the catenary mechanism. This result suggests that the duration of the catenary mechanism, rather than the magnitude of the axial force, plays an essential role in the resistance of vertical load.

梁到柱的连接配置，例如焊接，螺栓连接和混合焊接-螺栓连接，在拆除中柱的情况下，对结构的抵抗力和延展性起着重要的作用。本文说明了在渐进倒塌情况下具有不同连接细节的两个钢框架组件的全面实验室测试。一个样本采用改进的常规技术，该技术具有增强的焊接法兰螺栓腹板连接（SC-WR），而另一个样本则使用基于前者（SC-WB）的开槽孔连接。在测试中分析了失效模式，载荷传递机制和垂直电阻。两种连接配置均具有令人满意的负载电阻和延展性。试样SC-WB由于采用改良的螺栓剪力片进行了足够的应力重新分配，因此在后来的悬链线阶段显示出更高的极限竖向承载力和更大的弦旋转。此外，开发了有限元模型（FEM）并根据测试数据进行了验证。FEM可以准确地模拟试样的机械行为和破坏，从而可以为类似工作条件下的梁柱连接配置提供有效的参考。最后，根据实验和数值结果展示了简化的力学模型，以揭示悬链线机理的作用。该结果表明，悬链机构的持续时间，而不是轴向力的大小，在垂直载荷的抵抗中起着至关重要的作用。