Effects of thermal expansion and support restraints on performance of composite floors in fire

This paper presents results of a numerical study on the effects of thermal expansion and support restraint conditions on the performance of composite floors in fire. Previously, two full-scale composite floor specimens were tested to investigate factors, such as the supports restraint conditions, that affected the failure of the World Trade Center buildings? floors. Although higher fire resistance was expected for the restrained floors, the test results showed higher fire resistance rating for the unrestrained floor specimen. The purpose of this research was to understand the rationale behind these results numerically. The structural analysis software SAFIR was employed to evaluate the response of the composite floor specimens in fire, such as strain and stress distributions and floor deflection. The results show that the concrete spalling during the first hour of the test for the restrained specimen would have been due to concrete compression failure caused by the restraint condition and thermal expansion.Nous pr\ue9sentons dans ce document les r\ue9sultats d?une \ue9tude num\ue9rique portant sur les incidences de la dilatation thermique et des conditions de contrainte des supports sur la performance des planchers en mat\ue9riau composite expos\ue9s \ue0 l?incendie. Auparavant, on avait mis \ue0 l?essai deux (2) \ue9chantillons en vraie grandeur de plancher en mat\ue9riau composite dans le but d?investiguer des facteurs tels que les conditions de contrainte des supports ayant jou\ue9 sur la d\ue9faillance des planchers des tours du World Trade Center. Bien qu?une tenue au feu sup\ue9rieure \ue9tait escompt\ue9e des planchers contraints, les r\ue9sultats des essais ont r\ue9v\ue9l\ue9 que c?\ue9tait au contraire l?\ue9chantillon de plancher non contraint qui offrait cette caract\ue9ristique. Le but vis\ue9 par cette recherche \ue9tait de mieux comprendre le fondement de ces r\ue9sultats num\ue9riques. Le logiciel d?analyse structurale SAFIR a \ue9t\ue9 employ\ue9 pour \ue9valuer la r\ue9ponse des \ue9chantillons de plancher en mat\ue9riau composite expos\ue9s au feu, par exemple, les valeurs de distribution des tensions et contraintes et le fl\ue9chissement des planchers. Les r\ue9sultats montrent que l?effritement du b\ue9ton au cours de la premi\ue8re heure de l?essai pour l?\ue9chantillon contraint aurait \ue9t\ue9 attribuable \ue0 la d\ue9faillance en compression du b\ue9ton caus\ue9e par la condition de contrainte et de dilatation thermique.Peer reviewed: YesNRC publication: Ye