A new finite element model for steel–concrete side–plated beams exposed to mechanical and fire-like thermal loading is presented. The moisture and heat transfer through concrete is considered to be 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 Bićanić 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 of the section. A novel, strain-based finite element formulation of the planar beam is proposed for 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 confirmed, particularly when higher levels of the service load are applied to the beam.
COBISS.SI-ID: 6309217
A new mathematical model and its analytical solution for the analysis of the stress-strain state of a linear elastic beam cracked in flexure and strengthened with plates on its lateral sides is presented. Both the longitudinal and the transversal interactions at the side plate/beam interface are considered. Linear behaviour of the contact connection is assumed. The method is based on the linearised planar beam theory of Reissner. The weakening of the beam induced by the flexural crack is modelled conventionally as a rotational spring. The suitability of the theory is demonstrated in a case presentation involving the comparison between analytical results of the present beam (1D) model, the experiments and the numerical results of a full 3D solid model created in the LUSAS finite element analysis software. An excellent agreement between the results is observed, so that the proposed formulation is found to be both accurate and reliable. Finally, the solution is employed in an engineering design, discussing the effects of the material and the geometric properties of selected characteristic cases of the observed beams on the static and kinematic quantities, including the boundary conditions of the side plates, the longitudinal and the transversal stiffness of the connection, the size of the cracks, the span of the beam, and the length and the stiffness of the sideplates. For the cracked cantilever beam, a substantial effect of any of these parameters on the results is confirmed. In contrast, for the cracked two-span continuous beam, only the effects of the stiffness of the side plates and the length of the beam spans are noticeable.
COBISS.SI-ID: 6031457
In the paper a novel three-step finite-element numerical model for the fire analysis of side-plated reinforced concrete (RC) beams is presented. Advantages of beam side reinforcing as a way of structural retrofitting are explored for the selected case and an important contribution of the side plates to the ultimate fire resistance of the RC beam is observed.
COBISS.SI-ID: 6237537