||Integrity of Steel Gravity Framing Systems|
a Milek Fellowship project
||Jeffrey Berman in collaboration with J. Liu and L. Fahnestock|
||University of Washington, Purdue, and University of Illinois at Urbana-Champaign|
||2008 - 2014|
Overview and Objectives: The research aims to investigate the behaviors, component demands and component capacities that contribute to the integrity of steel framing when critical members are damaged. To mitigate progressive or disproportionate collapse, steel frames must redistribute gravity loads and form alternative load resisting mechanisms. In developing these mechanisms, components are subjected to strength and deformation demands for which they have not been designed. There is a clear need to address this problem as code bodies begin to develop requirements that may be difficult to achieve in practice and may miss performance targets.
A few primary objectives include:
Investigate the response of steel gravity frame systems under loading when loss of load carrying capacity of a column occurs.
Develop estimates of the demands on steel gravity frame connections when a column in the system is compromised.
Investigate the behavior of typical steel gravity frame connections under the combination of loadings, i.e., tension, shear and flexure, which occur in the system when it undergoes large vertical deformation at a compromised column.
Work Description: A glimpse of the first three of five research tasks:
Task 1: Use analytical models adapted from the literature and modified to develop estimates of connection demands in the scenario of column removal.
Task 2: Experimentally evaluate standard gravity frame beam-to-column connections under the estimated demands, which are combined rotation and axial deformation demands.
Task 3: Develop high resolution finite element models of the connections for further investigation of their behavior.
Deliverables: Produced from this research will be clear and consistent recommendations for designing steel structural systems with optimum integrity.
Benefit: The research will also produce practical solutions to improve connection performance and system integrity.
- The support by AISC has also enabled the development of a National Science Foundation proposal that was recently selected for funding.
- Task 1 is complete and the fiber models have been developed to estimate connection demands in a column loss scenario.
A test setup has been designed to test gravity frame connections and the major components have been fabricated.
(images courtesy of Dr. Berman)