Computational algorithm for the verification of reinforced concrete sections in fire situation

Abstract

Reinforced concrete structures may have reduced strength due to the degradation of their mechanical properties by temperature. This can increase the risk of structural collapses. Thus, the structural design should consider its behavior at room temperature and in fire situation (ABNT NBR 14432:2001). This study presents the development of an algorithm to verify the strength of any reinforced concrete sections subjected to unsymmetrical bending at room temperature and in fire situation. For this purpose, a stress integration algorithm was implemented from the strain profile of the section according to ABNT NBR 15200:2012, linked to a finite element mesh generator and a thermal analysis algorithm. For validation of the developed program, called Pisafo, the results obtained were compared with those in the technical literature: obtained in experiments (with differences of up to 28.5%) and with recognized software solutions (with differences of up to -14.8%). The largest variations in relation to the experiments can be attributed to the differences between the thermal properties of the concrete in the experiments with those prescribed in the technical standards used by the program and the non-consideration of spalling in the computational analysis.

Numerical evaluation of aggregate size influence on concrete mechanical damage under high temperatures

“…Srivastava and Prakash [15] developed a novel coupled framework for analysis of reinforced concrete and steel planar frames subjected to fire with three-way coupling between heat transfer, mechanical deformations and pore pressure build-up and used several numerical examples to demonstrate the accuracy and applicability of the framework. Padre et al [3] implemented an algorithm to check the resistance of reinforced concrete sections to oblique unsymmetrical bending at ambient temperature and in a fire situation. Magisano et al [16] proposed an automatic procedure for evaluating the axial force-biaxial bending yield surface of reinforced concrete sections in fire and a strategy to determine the limit fire duration, that is, the time of exposure which leads to structural collapse.…”