Evaluation of Column Cracking in Steel Moment Frames

由于北岭地震，大约50座钢框架建筑出现了罗德裂缝。人们对这些结构上使用的焊接实践和程序表示了相当大的关注。这些焊接问题显然是很好的安置，但它不太可能是钢架开裂的唯一来源。裂纹进入钢柱和面板区域的进展表明，除焊缝外，还有其他因素影响了这一过程。与此同时，在过去的10年里，钢框架的专业实践和抗震设计规范也发生了变化。该研究项目将确定最近地震设计实践的变化是否与焊接相结合并导致了开裂问题。研究将检查开裂的原因和可能的解决方案。布兰道和约翰斯顿咨询公司的分包合同将参与这项研究，提供设计图纸、详细建议、实用见解和有关受损建筑的信息。将选择三栋建筑进行调查。将利用建筑物所经历的振动的最佳可用信息，对结构进行一系列的整体弹性和非弹性分析。关键区域的详细弹性和非线性分析将用于检查薄弱环节，屈服和开裂的顺序以及关键部件的估计阻力。将预测和检查替代设计条款对UBC条款的影响。将进行一系列有限的试验来检验焊接效应，这些试验将与分析结果相关联。这是北岭地震项目。＊＊＊

9416112 Roeder Cracking has been noted on approximately 50 steel frame buildings as a result of the Northridge Earthquake. Considerable concerns have been expressed about the welding practice and procedures used on these structures. These welding concerns are clearly well placed, but it is unlikely that these are the sole source of the steel frame cracking. The progression of cracking into the steel column and panel zone suggest that factors in addition to the welds affect the process. At the same time, there have been changes in the professional practice and seismic design codes for steel moment frames during the past 10 years. This research project will determine if the recent changes in seismic design practice have combined with welds and contributed to the cracking problem. The research will examine the cause of cracking and possible solutions. A subcontract to the consulting firm of Brandow and Johnston will be involved in this study to provide design drawings, detailed advice, practical insight and information on the damaged buildings. Three buildings will be selected for investigation. A series of global elastic and inelastic analysis of the structures will be performed using the best available information for the shaking experienced by the buildings. Detailed elastic and nonlinear analysis of critical areas will be used to examine the weak links, the sequence of yield and cracking and the estimated resistance of the critical components. The effect of alternate design provisions to the UBC provisions would be predicted and examined. A limited series of experiments examining weld effects will be performed, and the experiments will be correlated to the analytical results. This is a Northridge Earthquake project. ***