Analytical and Experimental Investigation of the Effects of Member Deterioration on Seismic Response of Steel Frame Systems

直到最近，钢框架建筑一直被认为是在地震灾区使用的最好的结构体系之一。然而，加州北岭、洛马普里塔等地震导致许多焊接钢框架建筑的脆性断裂，日本神户地震期间类似建筑的严重破坏，包括倒塌，以及最近的研究，导致许多人对这一断言提出质疑。已开始对钢焊接件和连接的基本性能进行研究。然而，局部断裂和强度劣化对体系整体性能的影响尚不清楚，本项目将对各种形式的构件强度劣化对体系整体性能的影响进行综合的试验和分析评估。研究了以焊接钢框架结构为代表的二维框架体系的模型，以了解各种类型的强度劣化和地面运动对整体性能的相对贡献，并评估由强度劣化引起的力的动态重新分配的影响，以及系统冗余对整体性能的影响。特别注意以下后果：(A)与脆性连接失效相关的突然强度损失和(B)屈服后强度的逐渐恶化，这可能与局部屈曲或侧向扭转屈曲引起的延性响应有关。将对各种框架系统进行分析研究。将对由可更换的塑性铰区制成的平面框架试件进行振动台试验，这些试件表现出包括脆性断裂在内的各种形式的劣化，并将试验结果与分析结果相结合，以制定设计建议。

Until recently, steel frame buildings have been considered to be among the very best structural systems for use in regions subjected to earthquakes. However, the brittle fracture of many welding steel frame buildings as a result of the Northridge, Loma Prieta and other earthquakes in California, the serious damage, including collapse, of similar buildings during the Kobe Japan earthquake, and recent research have led many to question this assertion. Research has been initiated on the basic properties of steel weldments and connections. However, the impact of local fracture and strength deterioration on the overall performance of a system is still not understood.An integrative experimental and analytical assessment will be conducted in this project of the effects on overall system behavior of various forms of member strength deterioration. Models of two-dimensional frame systems representative of welded steel frame buildings are investigated to understand the relative contribution of various types of strength deterioration and ground motions on overall performance and to assess the effect of the dynamic redistribution of force caused by strength deterioration, and assess the role of system redundancy on global performance. Particular attention is directed at the consequences of (a) sudden loss of strength associated with brittle connection failures and (b) gradual deterioration of post-yield strength that may be associated with ductile response due to local buckling or lateral torsional buckling. Analytical studies will be conducted on a variety of framed systems. Shaking table tests with planer frame specimens made of replaceable plastic hinge regions which exhibit various forms of deterioration, including brittle fracture will be carried out and the test results will be integrated with analytical results to formulate designs recommendations.