1 XTRACT: A Tool for Axial Force - Ultimate Curvature Interactions C.B. Chadwell 1 and R.A. Imbsen 2 1 Assistant Professor, Department of Civil and Environmental Engineering, California Polytechnic State University, San Luis Obispo, CA 93407: [email protected]. 2 President, Imbsen & Associates, Inc., 9912 Business Park Drive, Suite 130, Sacra- mento, CA 95827: [email protected]. Abstract XTRACT (Chadwell and Imbsen, 2002) started as an academic and research tool at the University of California at Berkeley as a program titled UCFyber. At its infancy, UCFyber was the first interactive Microsoft Windows based program that performed moment curvature analysis for reinforce concrete cross sections. The program had the capability of performing realistic analysis of cross sections incorporating the effects of increased strength and ductility of confined concrete as well as nonlinear steel behavior within a graphical environment. While XTRACT has become an invaluable instrument for concrete research within earthquake engineering, it has also evolved to become a production tool for analysis and design of concrete systems within design offices around the World. XTRACT is an important tool for earthquake engineering analysis when a realistic assessment of moment and curvature capacities of a cross section is required. XTRACT has been used on many high profile projects for both buildings and bridges ranging from analysis of the existing columns for the Salt Lake City, City Hall seismic upgrade project to analysis of the suspension bridge columns on the new Caquenez Straits bridge in the San Francisco Bay Area. In addition, XTRACT is currently being used in the design of the temporary bypass structure for the new San Francisco-Oakland Bay Bridge as well as in numerous state transportation agencies across the country. This paper discusses some of the basic analytical features within XTRACT and intro- duces some innovative uses of the program for seismic assessment of reinforced con- crete columns. During seismic excitation of concrete moment resisting frames axial forces vary due to overturning demands. This, in turn, affects the ultimate curvature capacity and consequentially, the seismic displacement capacity of the concrete col- umns. By generating a plot of axial force verses ultimate curvature, curvature demands can be checked directly for a concrete column within a seismic force resisting frame. This paper outlines the methodology behind the creation of this type of diagram and includes example diagrams for both unconfined and confined rectangular concrete cross sections.
XTRACT: A Tool for Axial Force - Ultimate Curvature Interactions
Jul 01, 2023
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