Grant: $590,391 - National Science Foundation - Jul. 24, 2009
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Award Description: An innovative technique for improving seismic performance of steel beam-column connection with the advantages of the reduced beam section (RBS) connection, but with improved energy dissipation. Through a pilot study the concept is validated numerically at NC State University. This proposed research will conduct a systematic set of beam-column connection experiments for evaluating the novel seismic performance enhancement concept. The novel concept involves heat treating sections of beam flanges by exposing these sections to very high temperatures for certain amount of time before slow air cooling. Such heat treatment reduces the strength of steel in the heat treated areas of the flange. Consequently, under seismic loading plastic hinge develops at the heat treated beam section (HBS). Among the three moment resisting connections prequalified for special and intermediate moment frames by the 2005 AISC 358 standards, the reduced beam section (RBS) is the most popular because of its seismic performance and cost effectiveness. In the RBS connections, ?weakening? of the beam flanges induces plastic hinge away from the welds. In case of the HBS connections, plastic hinge develops at the heat treated beam section where steel strength is reduced by the heat treatment. As the beam flange dimensions, and the elastic and plastic moduli of steel are not altered in the HBS connection, the lateral and torsional buckling resistance of the HBS connection is higher than the RBS connection. Consequently, the HBS connections will dissipate a larger amount of energy with a minimum loss of strength or stiffness than the RBS connections. The proposed research will experimentally validate this novel seismic performance enhancement concept, and develop the design methodology for implementing the concept. The proposed research will conduct seven seismic experiments on the HBS beam-column connections to evaluate their seismic performance. The novel seismic performance enhancement technique will be validated on the welded unreinforced flange-bolted web (WUF-B) connection and hence an additional experiment on WUF-B connection (without heat treatment) will be conducted for reference. Strains, displacements and rotations at various locations will be recorded for investigating both the local and global failure mechanisms of the HBS connections. In the first step, a set of monotonic and cyclic material experiments on heat treated coupons will be conducted. The material coupons will be heat treated by exposing to various peak temperatures in the range of 800-1150oC and two hold times at peak temperatures. This set of material data will be analyzed to quantify the influence of heat treatment on material responses and used to determine the constitutive model parameters of the Chaboche model in ANSYS. A series of finite element analyses of the HBS connection using the Chaboche nonlinear kinematic hardening model will be performed to determine the optimum heat treatment parameters: i) maximum temperature and hold time, and ii) length of the heat treated flange section and, and iii) offset of the heat treated section from the column flange. The seismic performance of the HBS connection with i) both the top and bottom flanges are heat treated (new construction), and ii) only the bottom flange is heat treated (existing building) will be evaluated experimentally. Finally, based on the experimental and finite element analysis data a design methodology for the novel HBS connection will be developed.
Project Description: The activities of this project will start from January 2010. Hence no activity report at this time.
Jobs Summary: No employees have been hired as of the report date (Total jobs reported: 0)
Project Status: Not Started
This award's data was last updated on Jul. 24, 2009. Help expand these official descriptions using the wiki below.