# HIGH TEMPERATURES INFLUENCE ON THE REINFORCED CONCRETE PANELS STRENGTH THROUGH THE LIMIT ANALYSIS THEORY

## Palavras-chave:

reinforced concrete panels, limit analysis theory, high temperatures, thermal analysis, fire loading## Resumo

The constitutive behavior of reinforced concrete (RC) structures is significantly altered when

exposed to high temperatures. The high thermal gradients cause deterioration of the thermo-mechanical

properties of the materials together with thermal-induced deformations, which in turn modify the

geometry of the structure. The aim of the present work is to evaluate the influence of fire occurrence on

the stability of the RC panel structures, through the limit analysis theory. By modelling the panel as a

beam, determining the interaction diagrams for each time of fire exposure is the first step. The

temperature profiles along the sections of the panels are obtained numerically and the interaction

diagrams by integrating the concrete and steel strengths along the section with explicit account for the

different parameters controlling the problem, such as the section thickness, reinforcement area and

concrete compressive strength. The second step consists in determining the deformed configuration of

panel and associated distribution of axial and bending moment efforts, considering the second order

effects caused by the eccentricity of the self-weight load induced by the thermal deformations. This is

achieved by analyzing the thermo-elastic equilibrium of the panel under the combined action of thermal

gradient induced by fire and self-weight loading. The analysis is done by overlapping the interaction

diagrams of the sections and the distribution of internal efforts along the structure. Several numerical

examples are presented to assess the effect of relevant parameters on the overall fire safety of the

structure, emphasizing the effectiveness of the approach for design purposes.