COMPARAÇÃO DOS PARÂMETROS DE MODELOS CONSTITUTIVOS MODIFICADOS DE CARREIRA E CHU PARA UHPC ATRAVÉS DE REGRESSÃO NÃO LINEAR

Abstract

The Carreira & Chu (1985) constitutive model, which describes the stress-strain behavior of concrete under simple compression, is widely employed in analyses of cementitious matrices due to its simplicity. However, this model has limitations when dealing with concretes and mortars containing fibers, as is the specific case with UHPC. To overcome these limitations, modifications to the model have been proposed by Ezeldin & Balaguru (1992) and by Mansur et al. (1999). This study aims for a computational approach using nonlinear regressions, developed in the R language, and Leverberg–Marquardt optimization for parameter adjustment for the compression behaveor of UHPC. The validation data were obtained from compression tests on UHPC with the addition of 1% and 2% metallic fibers. The models satisfactorily converged to the performed tests. The model by Mansur et al. (1999) stood out mainly in representing post-peak behaviors.