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In recent years confinement requirements for concrete columns have increased in seismic regions. Steel jackets are one way to confine reinforced concrete columns. The increased confinement provides additional strength and ductility for the columns during seismic events. For reinforced concrete columns with steel jackets, there are different section properties in the jacketed and non-jacketed regions. The variation can cause difficulties modeling the seismic response of these columns. A plastic hinge integration method, derived from the modified two-point Gauss-Radau quadrature rule, is used to model steel jacketed columns with force-based finite elements. This integration method allows for the specification of the plastic hinge length in the element, thereby confining the spread of material nonlinear response to selected regions. Controlling the location of material nonlinear response provides an objective numerical solution for strain-softening behavior that occurs due to the crushing of concrete. In addition, different material properties can be specified for the jacketed and non-jacketed regions, which allows for only one frame element to be used in modeling. This integration method is verified for elements with different material properties using a single force-based beam-column element. After the verification, the integration method is validated against experimental data from tests of steel jacketed reinforced concrete bridge columns conducted at the University of California at San Diego. The results of this research will be incorporated in pushover analysis software, developed at Oregon State University, for Alaska-style bridge bents. |
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