Section Discretization of Fiber Beam-Column Elements for Cyclic Inelastic Response

The paper presents studies of the effect of the number of material integration points at the monitored sections of fiber beam-column elements on the local response of typical structural cross sections under an extensive set of cyclic biaxial load conditions with constant and variable axial load. The study covers wide-flange steel sections and rectangular reinforced concrete sections. The integration over the section uses the midpoint rule and shows that a standard section discretization with relatively few fibers is a good compromise between accuracy and economy of means. The proposed coarse section discretization schemes are computationally efficient while ensuring the accurate representation of important aspects of the three-dimensional response of structural members, such as interaction of axial force with biaxial bending moment, effect of residual stress in steel members, and effect of cracking in reinforced concrete members. The local strain response is also represented with good accuracy by the coarse discretization schemes. DOI: 10.1061/(ASCE)ST.1943-541X.0000501. (C) 2012 American Society of Civil Engineers.