Composite beams under fire loading: numerical modeling of behavior

Purpose - The purpose of this study was to develop a three-dimensional (3D) finite element modeling (FEM) technique using the commercially available program ABAQUS to predict the thermal and structural behavior of composite beams under fire loading. Design/methodology/approach - The model was benchmarked using experimental test data, and it accounts for temperature-dependent material properties, force-slip-temperature relationship for the shear studs and concrete cracking. Findings - It was determined that composite beams can be modeled with this sequentially coupled thermal-structural 3D FEM to predict the displacement versus bottom flange temperature response and associated composite beam failure modes, including compression failure in the concrete slab, runaway deflection because of yielding of the steel beam or fracture of the shear studs. Originality/value - The Eurocode stress-strain-temperature (sigma-epsilon-T) material model for structural steel and concrete conservatively predict the composite beam deflections at temperatures above 500 degrees C. Models that use the National Institute of Standards and Technology (NIST) stress-strain-temperature (sigma-epsilon-T) material model more closely match the measured deflection response, as compared to the results using the Eurocode model. However, in some cases, the NIST model underestimates the composite beam deflections at temperatures above 500 degrees C.