Fire Behaviour of a Prestressed Thin-Walled Concrete V-Beam

Augusto Pedron,Nicola Tondini

doi:10.1007/s10694-021-01149-3

Abstract

The present work investigates the fire behaviour of a prestressed thin-walled concrete V-beam with variable cross section along its longitudinal axis. In particular, the results obtained from different modelling strategies implemented through analytical computations and Finite Element (FE) thermo-mechanical analyses conducted both with Euler–Bernoulli beam elements and with shell elements were compared. The models were able to properly allow for the prestressing force and its variation with temperature. The mode of failure was analysed both at ambient temperature and at elevated temperature by employing the ISO 834 standard heating curve as well as parametric fire curves so as to investigate the behaviour in the cooling phase. The outcomes showed that the beam model was not capable of accurately predicting the failure mode by largely overestimating the time of collapse. Indeed, the FE analysis with shell elements highlighted that beam behaviour assumptions with sections that remain plane were not satisfied as fire progressed. Furthermore, it also showed that the failure mode was not flexural in the longitudinal direction but due to the failure of the webs in transverse bending that interacted with longitudinal stresses. Finally, the analyses conducted by applying parametric fire curves highlighted possible failure in the cooling phase, which emphasises the need of careful analysis for these types of structural members.

Highlights

Industrial buildings are often made of precast concrete elements because of ease and speed of erection
The present work aims at examining the performance of a prestressed thin-walled concrete V-beam with variable cross section along its longitudinal axis subjected to the ISO 834 heating curve and parametric fire curves by carrying out a comprehensive comparative numerical thermo-mechanical analysis with different modelling strategies
It is evident that a shell-based modelling provides more insight into the fire behaviour of such a beam, for which a careful analysis is recommended

Summary

Introduction

Industrial buildings are often made of precast concrete elements because of ease and speed of erection. Bamonte et al [15] found that by analysing the load-bearing capacity in fire of an inverted V-section, shear is more dangerous than flexure They studied the mechanical response analytically based on the thermal field obtained through finite element analysis. Careful investigation on the structural fire behaviour is required and from the state of the art it emerges that, despite the extensive use of such structural members in the design practice, there is a lack of research works on the topic In this respect, the present work aims at examining the performance of a prestressed thin-walled concrete V-beam with variable cross section along its longitudinal axis subjected to the ISO 834 heating curve and parametric fire curves by carrying out a comprehensive comparative numerical thermo-mechanical analysis with different modelling strategies. Fire Behaviour of a Prestressed Thin-Walled Concrete bed; in Sect. 4 the results of the mechanical analyses are comprehensively reported and discussed; in Sect. 5 conclusions are drawn

Description of the Case Study and Numerical Modelling

Thermal Analysis

Findings

Conclusions