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Associate Professor Keith J. Kowalkowski received a $120,000 grant from the American Institute of Steel Construction to study the influence of eccentricity on stiffeners designed to resist concentrated forces applied to structural steel columns.
The co-primary investigator on the grant is Xin Xie, assistant professor of Mechanical Engineering at LTU. Xie is an expert in optical stress and strain analysis and will assist in interpreting experimental results. Another key contributor to the project is Javier Rodilla, an undergraduate student in civil engineering working on the project, who transitioned in the summer of 2018 to a graduate research assistant.
Steel structures are made of vertical columns and horizontal beams. Column stiffeners are used to reinforce the columns, which are subjected to concentrated forces from beam flanges or flange plates, often as part of a moment connection – defined as a connection that limits relative rotation between the beam and the column. Stiffeners are required when the column alone fails one of the various failure mechanisms associated with concentrated forces. Ideally, the stiffeners are placed in-line, or “concentric,” with beam flanges or flange plates, welded adjacent to the column flanges.
Kowalkowski’s project consists of experimental and analytical research. LTU undergraduate and graduate students will perform various tasks associated with both sides of the research. The project will consist of a full-time graduate research assistant and undergraduate research assistants as well. They will be conducting experiments on steel wide flange members in LTU’s Structural Testing Center, using a hydraulic actuator with a capacity up to 220,000 lbs. and using digital image correlation to capture and display results.
Under the study, three different experimental test methods will capture various column failure modes. Ten tests will be performed on columns without stiffeners, 10 equivalent tests will be performed on columns with concentric stiffeners, and 20 tests will be performed on columns with eccentric stiffeners, in which the eccentricity will be up to six inches.
The end result of the study will be final recommendations for steel construction practice, and suggested revisions to the AISC design guides and specifications. The results will also be published in the AISC Engineering Journal.
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