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

E P G Padre,R C S S Alvarenga,R C Silva,J C L Ribeiro

doi:10.1590/s1983-41952019000400012

E P G Padre, R C S S Alvarenga + Show 2 more

Open Access

https://doi.org/10.1590/s1983-41952019000400012

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Abstract

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.

Highlights

According to Brushlinsky et al [1], in 2014, in 23 countries surveyed, there were recorded a total of 819,265 fires in buildings, involving thousands of people injured and killed, as well as a financial loss of millions of dollars caused by the fires
A computational algorithm, called Pisafo, was developed to verify any sections of reinforced concrete subjected to unsymmetrical bending at room temperature and in fire situation
Pisafo allows the use of any fire curve in thermal analysis as well as various cross-sectional shapes by having a finite element mesh generator incorporated into the program

Summary

Introduction

According to Brushlinsky et al [1], in 2014, in 23 countries surveyed, there were recorded a total of 819,265 fires in buildings, involving thousands of people injured and killed, as well as a financial loss of millions of dollars caused by the fires. In relation to the decay of mechanical properties of the concrete with the temperature, this can be attributed to the physical-chemical changes in the cement paste and in the aggregates, and to the difference in the thermal deformations between these [26] In this way, the greater problems caused in the reinforced concrete structure occur at temperatures in the range of 500 °C to 600 °C [27]. With respect to the main mechanical properties of the materials composing the reinforced concrete, it can be mentioned the modulus of elasticity, the tensile and compressive strength and the stress-strain relationships [29] In this context, there are no studies on the development of an algorithm for the verification of the strength of any sections of reinforced concrete when subjected to unsymmetrical bending. This study aimed to present a computational algorithm capable of (a) Pop-out

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