An Advanced Transient Concrete Model for the Determination of Restraint in Concrete Structures Subjected to Fire

Abstract

The advanced transient concrete model (ATCM) is an extended model for concrete in compression at elevated temperature that incorporates elastic, plastic and creep strain as a function of temperature and stress history. The ATCM is applied with the material model of the thermal induced strain model. The non-linear model comprises thermal strain, elastic strain, plastic strain and transient temperature strains and load history modelling of restraint concrete structures subjected to fire. The mechanical strain is calculated as a function of elastic strain, plastic strain and thermal induced strain. The thermal induced strain is relative independent compared to dependence of Young's modulus by load history. Actually the term comprises elastic, plastic and (pure) transient creep strains as we will show. A comparison is given between experimental results with cylindrical specimens and calculated results. The equations of the ATCM consider a lot of capabilities, especially for considering the irreversible effects of temperature on some material properties. By considering the load history during heating up, an increasing load bearing capacity due to a higher stiffness of concrete may be obtained. With this model it is possible to apply the thermal-physical behaviour of material laws for calculation of structures under extreme temperature conditions. The effect of load history in highly loaded structures under fire load will be investigated. The theoretical basis is given in this paper.

A formulation of the Eurocode 2 concrete model at elevated temperature that includes an explicit term for transient creep

“…Concrete has a memory and concrete models have been developed in the literature to take into account the effect of the load history before heating [2] and during heating [23,24] on the deformation response to a change in stress and temperature increase. This effect has not been taken into account in the present model because of uncertainties on the hypothesis to be made for Author preprint version -Gernay, T., Franssen, J.M.…”

Effects of transient creep strain on post-tensioned concrete slabs in fire

“…Generally, the strain is separated from the total strain measured from the concrete specimen under constant load subjected to transient heating. Models accounting for transient strain under uniaxial compression have been proposed by many researchers -Anderberg and Thelandersson's model (Anderberg and Thelandersson, 1976), Diederichs's model introduced by Li and Purkiss (2005) and Youssef and Moftah (2007), Schneider's model (Schneider and Schneider, 2009), Terro's model (Terro, 1998), Nielsen's model described by Pearce et al (2004) and Gernay and Franssen's model (Gernay and Franssen, 2012). Nielsen's model may be much more applicable for various kinds of concrete because it has three parameters to be identified based on test data.…”