Columns in steel moment resisting frames can be subjected to high axial loads coupled with large lateral cyclic displacement demands during strong seismic events. Under such conditions, the occurrence of plastic hinging can introduce local buckling, which interrupts the load path and can synergistically promote other types of instabilities, such as flexural or lateral torsional bucking. The mechanisms by which such instabilities adversely interact to reduce the load carrying capacity of steel columns have not yet been investigated and are the focus of this research. Using analytical modeling and high fidelity computational simulation, fundamental studies will be conducted to investigate the vulnerability of steel moment frame systems associated with poor column performance. The studies will address the inelastic behavior of steel wide flange columns and connection subassemblies under large axial loads and lateral displacements and determine the role that local and global buckling of columns plays in promoting vertical progressive collapse of a structure during and after a seismic event. The models developed as part of this study will play a major role in moving performance-based design to the next level. Moreover, the findings of this planning grant research will provide key insight toward the development of test matrices for a future experimental program that will use NEES2 capabilities to further explore the problem.
Columns in steel frame buildings are the last line of defense against collapse. Such members are heavily loaded and subjected to severe demands during strong seismic events. Developing a clear understanding of how their load-carrying performance degrades under severe loading regimes will have a significant impact on how structural engineers design steel frames in seismic regions. By understanding the potential vulnerabilities of steel columns and the load carrying system, more resilient and robust designs can be achieved that better protect lives and property during severe seismic events. The findings may also be applied to other hazards where there is potential for poor column performance. Visualization models developed as part of this research have the potential to improve steel structural design education and help students better envision how instabilities occur in steel structural members. A diverse pool of students at both the graduate and undergraduate level will be involved at all levels of this study, allowing them the opportunity to gain important experience in the behavior of steel members and seismic design. Simulation and metadata from this project will be made available through the NEES data repository. This award is part of the National Earthquake Hazards Reduction Program (NEHRP).
