Shear tab connection with composite beam subjected to transient-state fire temperatures

Abstract

Purpose This study aims to develop a rational model to predict the thermal axial forces developed in shear tab connections with composite beams when subjected to transient-state fire temperatures. Design/methodology/approach Finite element (FE) models are first developed in ABAQUS and validated against experimental data available in the literature. Second, a parametric study is conducted to identify the major parameters that affect the behavior of shear tab connections with composite beams in the fire. This includes beam length, shear tab thickness, shear tab location, concrete slab thickness, setback distance and partial composite action. A design-oriented model is developed to predict the thermal induced axial forces during the heating and cooling phases of a fire event. The model consists of multi-linear springs that can predict the stiffness and strength of each component of the connection with the composite beam. Findings The FE results show that significant thermal axial forces are generated in the composite beam in the fire. This is prominent when the beam bottom flange comes in contact with the column. Fracture at the toe of the welds governs the behavior during the cooling phase in most FE simulations. Also, the rational model is validated against the FE results and is capable of predicting the thermal axial forces developed in shear tab connections with composite beams under different geometrical properties. Originality/value The proposed model can predict the thermal axial force demand and can be used in performance-based approaches in future structural fire engineering applications.

Component Modeling for Fire Behavior of Shear Tab Connections

“…The bolt bearing, bolt shear, and friction components were then combined to create a component model that was validated against the experimental tests performed by Yu et al (2009). Hajjar et al (2019) developed a single analytical expression derived by mathematically combining component stiffnesses to calculate the response of the connection at different "stages" throughout the fire. A component representing the contact between the bottom flange of the beam Kurikova et al (2022) developed a component model for fillet welds to aid in the design of welded joints using a component-based finite element method (CBFEM).…”

“…Researchers have incorporated a variety of different stiffnesses and capacities for the gap/contact between the bottom flange of the beam and the flange of the column (Yu et al, 2009;Hajjar et al, 2019;Agarwal and Varma, 2014;Hu et al, 2009;Taib and Burgess, 2011). Some researchers (Yu et al, 2009;Agarwal and Varma, 2014;Taib and Burgess, 2011) defined the gap/contact component to initially have no stiffness (simulating the gap between beam flange and column) and extremely high stiffness with unlimited capacity (simulating contact of the beam flange with the column) when the deformation was equal to the distance of the gap.…”

“…However, this method does not consider deformation that may occur due to local buckling of the beam bottom flange. Hajjar et al (2019) defined the stiffness of the contact component to be equal to the axial stiffness of the bottom flange of the beam. Hajjar et al also reduced the area of the bottom flange of the beam by a factor of 0.7 because only 70% of the beam flange was assumed to be in contact with the column flange.…”

“…Although there is agreement in the literature that bolt bearing is a ductile failure mechanism, the amount of ductility incorporated within bolt bearing component models varies. Some bolt bearing components (Hajjar et al, 2019;Rex and Easterling, 2017;Sadek et al, 2008;Sarraj, 2007;Taib and Burgess, 2011;Weigand, 2017;Xie et al, 2018aXie et al, , 2018bYu et al, 2009) had infinite ductility. For others (Agarwal and Varma, 2014;Koduru and Driver, 2014;Sadek et al, 2008), ductile failure was assumed to be initiated after a specific deformation of the bolt holes.…”

“…Rotation of the beam ends can cause the bottom flange of the beam to have contact with the flange of the column it is connected to. Contact of the bottom beam flange and the column flange limits the rotational capacity of the connection, imposing large flexural demands on the connection and increasing compressive forces in the beam (Hajjar et al, 2019). At this point during the fire, the gravity connection designed for only shear force demand does not behave as an idealized pin.…”