A new finite element model for steel concrete side plated beams exposed to mechanical and thermal loading is presented . The moisture and heat transfer through concrete is considered independent on mechanical deformations . The hygro thermo mechanical analysis is performed in two separate steps starting with the moisture and heat transfer analysis and continuing with the mechanical stress strain analysis . The finite element model of Davie Pearce and Bi ani was implemented for the moisture and heat transfer analysis in the concrete part of the beam . The Fourier equation of heat transfer for non porous solids was applied in the steel part . A novel strain based finite element formulation of the planar beam is proposed to perform the mechanical part of the fire analysis . Each of the two steps of the model is first verified by comparing the present numerical results with the experimental and numerical data available in the literature . The finite element formulations of both the hygro thermal and the mechanical steps of the analysis are found to be reliable and accurate . Finally effects of the side reinforcing of a RC beam as one of the methods of structural retrofitting are explored in the case of a typical fire scenario and an important contribution of the side plates to the ultimate fire resistance of the beam is discovered particularly when higher levels of the service load are applied to the beam . mass of phase i per unit volume of gaseous material time heat capacity of concrete thermal conductivity of concrete energy transferred by the fluid flow specific heat of evaporation specific heat of dehydration mass of bound water released by the dehydration per unit volume of concrete absolute temperature degree of saturation with free water porosity of concrete degree of saturation with adsorbed water solid saturation point diffusion coefficient of dry air in water vapour diffusion coefficient of water vapour in dry air velocity in phase i the X and Z components of the cross sectional stress resultant of layer i the cross sectional axial and shear force of layer i and its differential area of the cross section of layer i and its differential cross sectional position vector of a specific particle of layer i with respect to the reference axis component of the slip vector the Z component of the slip vector contact traction vector total strain in a generic particle of layer i and the related strain ultimate concrete compressive strain water phase liquid water phase adsorbed water phase gas phase water vapour phase dry air phase concrete steel pore pressure contribution in the total stress of concrete effective stress contribution in the total stress of concrete external contribution in the traction vector components contact contribution in the traction vector components ambient temperature conditions conditions at elevated temperature horizontal direction vertical direction Gaussian integration node RC beam side plates 


Highlights:
A new finite element model for steel concrete side plated beams in fire conditions is presented. The fire analysis is performed in two separate steps i.e. hygro thermal and mechanical step. The proposed finite element formulations proved to be reliable and accurate. Side plates have impact on the ultimate fire resistance of the RC beam.