Effects of Welding Method, Loading Rate, and Loading Sequence on Fracture Behavior of Welded Steel Beam-to-Column Connections

本研究的目的是找出在1994年北岭地震和1995年兵库县南部地震中大量焊接梁柱连接断裂的原因。重点研究了梁柱焊接节点的焊接方法、加载速率和加载顺序，包括以下几个方面：（1）收集以往的试验数据，建立梁柱焊接节点数据库;（2）调查以往地震中的破坏模式;（3）以焊接方法、加载速率和加载顺序为参数的梁柱连接试验;（4）所得结果的综合和对新设计程序的建议。主要研究结果总结如下：（a）建立了一个包含以往梁柱焊接节点试验的数据库。连接的延性能力被发现分散非常显着。(b)对受损梁柱节点的调查表明， 关于我们 最终引起的断裂起始于焊接进入孔的趾部、溢流片、焊接尖端或焊接金属中的一个。(c)研究了不同类型的焊接通道孔，并量化了它们对连接延性能力的影响。结果发现，修改后的细节，其中的孔的大小被减少，可以确保更大的延性能力的2至3倍，与传统的细节。(d)对大地震作用下框架结构的数值分析表明，梁端承受的应变率在0.2~0.3/s之间。(e)与先前的推测相反，动态加载比准静态加载表现出更大的延性能力，断裂模式更具延性。动态加载过程中的显著温度升高被认为是这种失效模式的可能原因。(f)根据焊接通道孔的类型、预期的延性能力和破坏模式，提供了焊接梁柱连接的抗震设计指南。少

The objective of this research is to identify the reasons why so many welded beam-to-column connections fractured in the 1994 Northridge and 1995 Hyogoken-Nanbu Earthquakes. The focuses of the investigation are the welding method, loading rate, and loading sequence, and a study comprising the following steps was carried out : (1) collection of previous test data and development of database on welded beam-to-column connections ; (2) survey of damage patterns exhibited in the previous earthquakes ; (3) tests of beam-to-column connections with the welding method, loading rate, and loading sequence as parameters ; and (4) synthesis of obtained results and proposals for new design procedures. The major findings are summarized as follows :(a) A database that contains previous tests of welded beam-to-column connections was developed. The ductility capacity of the connections was found to scatter very significantly.(b) A survey on damaged beam-to-column connections revealed that cracks that ev … More entually caused fractures were initiated in one of the toe of the weld access hole, run-off tab, weld tip, or weld metal.(c) Various types of weld access holes were examined, and their effects on the connection ductility capacity were quantified. It was found that modified details in which the size of the holes was reduced can ensure greater ductility capacity by a factor of 2 to 3 compared to the conventional details.(d) Numerical analysis for frames subjected to large ground motions showed that the strain rate sustained by the beam end would be in a range of 0.2 to 0.3/s.(e) Contrary to previous speculation, dynamic loading exhibited larger ductility capacity than quasi-static loading, with the mode of fracture being more ductile. Significant temperature rise during dynamic loading was found to be a likely cause for this mode of failure.(f) Guidelines were provided as to the seismic design of welded beam-to-column connections in terms of the type of weld access holes, expected ductility capacity, and mode of failures. Less