Constitutive Model of Concrete Frame Structure Under Localized Fire Simulations

Abstract

In recent decades, special considerations have been given to the use of fire safety analysis on modern concrete buildings. The considerations include the stability of building which providing sufficient time for the occupants to evacuate and for firefighting. This paper is mainly concerned with the performance of concrete frame structure exposed to localized fire. From the simplified model, load carrying mechanism of concrete frame is identified and several design implications are discussed. Frame model in present analyses constructed of normal-strength reinforced concrete beams and high-strength reinforced concrete columns represented typical commercial office building. All elements of the frame are modeled using 3D tetrahedral coupled-field solid element defined by ten nodes with four degree of freedom. Temperature response predicted from previous researchers and loadings represented total design load at the fire limit state are applied. Constitutive model in a full thermal strain-stress analysis is employed on simple empirical formula. Three-dimensional finite element computer model using ANSYS considering transient effects gave reasonable results. The results indicate that behavior of individual isolated member accommodated by the current codes is different from the behavior of complete structure. Therefore, developing fire engineering analysis from the behavior of complete structures is strongly recommended.