Fire-Resistance of Eccentrically Loaded Rectangular Concrete-Filled Steel Tubular Slender Columns Incorporating Interaction of Local and Global Buckling

A mathematical model using the fiber approach is presented in this paper for quantifying the strength and fire-resistance of eccentrically loaded slender concrete-filled steel tubular (CFST) columns with rectangular sections incorporating the interaction of local and global buckling. The model utilizes the thermal simulator to ascertain the temperature distribution in cross-sections, and the nonlinear global buckling analysis to predict the interaction responses of local and global buckling of loaded CFST slender columns to fire effects. The initial geometric imperfection, air gap between the concrete and steel tube, tensile concrete strength, deformations caused by preloads, and temperature-dependent material behavior are included in the formulation. The computational theory, modeling procedure and numerical solution algorithms are described. The computational model is verified by existing experimental and numerical results. The structural responses and fire-resistance of CFST columns of rectangular sections exposed to fire are investigated. The mathematical model proposed is demonstrated to be an efficient computer simulator for the fire-performance of slender CFST columns loaded eccentrically

Minor Axis Flexure and Combined Loading Response of I-Shaped Steel Members

The present dissertation elucidates the problem of determining if a given I-shaped cross-section is properly proportioned to accommodate sufficient plastic hinge rotation capacity to facilitate the redistribution of moments in a structural system as needed to accommodate the formation of a collapse mechanism. It might be tempting to believe that application of the limiting flange plate slenderness value for the case of major axis flexure are applicable in this case; since the pervasive belief is that this approach ought to be conservative. However, the present research study indicates that this is not the case and thus more sophisticated analysis techniques are required to better understand this case. Most current design specifications employed throughout the world prescribe the use of so-called interaction equations for the design of beam-columns. Most often these interaction equations are optimized for use with the members possessing I-shaped cross-sections that are bent about the major principal centroidal axis while simultaneously being subjected to compressive thrust. The current study then also focuses on the case wherein an I-shaped member is loaded in compression and simultaneously bent about the minor principal centroidal axis. It is shown that the current AISC interaction equations can be improved on in terms of their ability to predict failure in these types of members. Alterations to the existing AISC interaction equations are suggested for improving on strength predictions relative to this case. Through these two research focuses, the present dissertation adds significantly to the state of knowledge surrounding the response of steel members possessing I-shaped cross-sections that are subjected to minor axis flexural effects; effects that are important to the robust and redundant design of structures in a system-wide sense