Effect of Material Parameters on Performance of Welded Steel Moment Frame Connections

材料参数对焊接钢弯矩框架连接性能的影响

• 批准号: 9821043
• 负责人: Claudia Ostertag
• 金额: $ 10.41万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-01 至 2002-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9821043&HistoricalAwards=false
• 关键词: Effect; Material; Parameters; Performance; Welded

More than 100 steel moment resisting frame buildings exhibited brittle connection fracture during the Northridge earthquake of 1994 and similar fractures were also observed following the Earthquake of 1995 in Japan. Despite extensive laboratory testing of large and small scale structures since then, factors leading to brittle fractures in these welded joints have not yet been identified. Recent studies on the causes for the brittle fracture have focused primarily on the structural design of these connections. However, local material properties of the steel in these welded joints are probably of equal importance to the causes and the failure of these connections. Design modifications in welded steel moment resisting connections deal with reducing global stresses. They do little to reduce local stresses. The aim of this research project is to develop a modified welding procedure specifically designed to ensure that ductile, fine grained microstructure will develop in the "critical region" of the connection where cracks commonly initiate due to the high stresses which are invariably present will be considerably reduced and triaxial stresses which are inherent in the connection will be less damaging due to the higher fracture toughness in the critical region. As a result the welded beam-to-column joint will exhibit and enhanced performance and brittle fracture may be avoided. The residual stresses due to welding will be measured by Scanning Acoustic Imaging of Stress, a newly developed acoustic microscopy technique, that allows stresses to be mapped with high spatial resolution. This research involves active collaboration with Japanese researchers at the University of Tokyo and Kyoto University in Japan.

在1994年的北岭地震中，100多座钢抗矩框架建筑出现了脆性连接断裂，1995年日本地震后也观察到类似的断裂。尽管从那时起对大大小小的结构进行了大量的实验室测试，但导致这些焊接接头脆性断裂的因素尚未确定。最近对脆性断裂原因的研究主要集中在这些连接的结构设计上。然而，这些焊接接头中钢材的局部材料性能可能对这些连接的原因和失效同样重要。焊接钢抗弯矩连接的设计修改涉及降低整体应力。他们对减轻当地的压力没有什么帮助。本研究项目的目的是开发一种改进的焊接工艺，以确保在连接的“关键区域”（通常由于高应力而引发的裂纹）中发展出延展性好、细晶粒的微观结构，这种结构将大大减少，并且由于在关键区域具有较高的断裂韧性，连接中固有的三轴应力将减少破坏性。结果表明，焊接梁柱节点具有良好的性能，可避免脆性断裂。焊接残余应力将通过扫描声成像测量，这是一种新开发的声学显微镜技术，可以以高空间分辨率绘制应力图。这项研究涉及与日本东京大学和京都大学的日本研究人员的积极合作。