Seismic Collapse Resilience of Buildings with Steel Moment Resisting Frames

deep steel columns;seismic design evolution;collapse analysis;resilience assessment;finite element simulation;seismic loading;Civil and Environmental Engineering;Engineering;Civil Engineering

Wu, Tung-YuSpence, Seymour Milton John ;

University of Michigan

关键词: deep steel columns;    seismic design evolution;    collapse analysis;    resilience assessment;    finite element simulation;    seismic loading;    Civil and Environmental Engineering;    Engineering;    Civil Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/149822/tungyuwu_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The use of deep steel columns, with a depth of 24 inches or greater, has been prevalent in special moment frames (SMFs) built since the late 1990s. The large depth, high in-plane flexural stiffness and strength make such sections an attractive choice for engineers seeking to satisfy current panel zone, drift and strong-column/weak-beam seismic design criteria. However, deep columns have potential vulnerabilities to local and global structural instabilities that are not yet fully understood. This dissertation presents an experimental and computational investigation designed to seek insight into the behavior of deep steel columns, buildings using them, and the seismic resilience of communities that contain such buildings. Nineteen half-scale T-section steel specimens, carefully proportioned and loaded to emulate the demands placed on deep columns under cyclic loading, are experimentally tested to investigate the effect of element slenderness ratios on cyclic flange local buckling and post-buckling response. The results show that column flanges that satisfy current highly ductile limits can suffer from significant strength degradation. A parallel computational study is used to expand the parameter space and further investigate the observations from the tests.The effects of slenderness ratios and initial axial load on the collapse capacity of first-story deep columns are studied using detailed computational models. The loading protocols and boundary conditions are selected to represent the demands associated with seismic-induced building collapse. Design-oriented expressions integrating all key variables are proposed to compute the compressive capacity of deep columns that meet the highly ductile criteria provided in the AISC seismic provisions.At the system level, two prototype frames and their variants are used to study the effect of deep columns on the collapse behavior of special moment frames. Collapse fragility curves of each frame are computed using incremental dynamic analysis. The curves suggest the need to brace beam-column connections at both beam flanges, regardless of the column-beam moment ratio. The simulations also show that slenderness ratios can be influential on system level response, and the level of column axial load should be limited to prevent an undesired collapse mechanism.The effect of design code evolution on the risks associated with using SMFs is investigated. Three code eras spanning the past half century are considered. High-fidelity models capable of explicitly capturing instabilities and fracture are employed to determine the effect of the differences in the designs. Retrofit strategies are proposed to improve the seismic resilience of communities with steel buildings. Overall, the findings provide the previously missing components to understanding of the influence of deep columns on the performance of buildings during an earthquake through experimental testing and detailed modeling at a full range of scales.