柱横向加劲肋(又称为连续板)的设置对梁柱焊接节点的延性有利的观点被普遍接受,美国AISC钢结构抗震规范规定节点必须在柱上设置连续板,除非试验表明节点没有柱横向加劲肋仍可以正常工作.然而,该规定是值得怀疑的,因为大量设置连续板的 T形节点试件表现较差的延性而没有连续板的节点试件表现很好的延性.为进一步研究连续板对 T 形节点延性的影响,对节点进行了单调荷载和循环荷载作用下的非线性分析,并应用几个力学参数来评估节点的延性,这些参数取自焊缝与梁翼缘界面处,因为该位置在较大塑性转角时应力状态接近临界条件.有限元分析结果表明:连续板的设置显著增加了焊缝与梁受拉翼缘界面处的塑性应变,导致节点延性的大大降低,表明设置于柱两侧的连续板是导致 T 形节点在地震作用下发生脆性破坏的主要原因之一.此外,通过文献资料中的试验数据进一步证明了该结论的正确性.
Effects of Column Transverse Stiffeners on Ductility of T-Shaped Welded Beam-to-Column Connections
It is generally believed that column transverse stiffeners(also known as continuity plate)will be beneficial to the ductility of the welded beam-to-column connections and the AISC Seismic Provisions for Structural Steel Buildings recommend the use of continuity plates in the column unless tests show that the connection will work without them.The provisions are questionable as many T-shaped connection specimens with continuity plates show little ductility while connections without continuity plates exhibit satisfactory ductility.To further investigate the effects of continuity plates on the ductility of T-shaped connections,nonlinear analysis of welded beam-column connections under both monotonic loading and cyclic loading was performed in the paper.Several mechanical parameters were employed to assess the ductility of the connec-tions.These quantities were sampled at weld-beam flange interface where the stress conditions were more critical at higher plastic rotation.The finite element analysis indicated that the plastic strain at the weld-beam tension flange interface was significantly increased due to the presence of continuity plates,which might cause a great reduction of ductility.Consequently,the analytical results demonstrated that the conti-nuity plate located on both sides of column web was one of mains causes which contributed to brittle failure of T-shaped exterior connections under seismic loading.The conclusion drawn from the paper was verified against experimental data available in the literature.
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