COMPARISON OF METHODS FOR HOMOGENIZING THE THERMAL PROPERTIES OF ULTRA-HIGH PERFORMANCE FIBER REINFORCED CONCRETE

Resumo

Ultra-high-performance fiber reinforced concrete (UHPFRC) stands out in the current context of civil construction as an alternative of great interest in the design of bold, slender and sophisticated structures. The performance under high thermal loads has been studied in order to understand the degradation of materials and a reduction in mechanical strength capacities, which indicates a loss of safety in structures. Computer simulations are a helpful tool for studying behavior patterns and identifying the mechanisms involved in the process of concrete damage when subjected to thermal stress. However, a challenge encountered in these models is the size difference between the fibers and the cementitious matrix in which they are embedded, which drives investment in homogenized models, as discrete modelling requires highly refined mesh generation and, consequently, high computational costs. In this context, this study aims to compare thermal models to represent the heating of synthetic UHPFRC specimens. Different models are discussed, including discrete fibers and homogenized systems, based on various methods in the literature. Analyses are carried out for concretes with fiber reinforcement rates ranging from 0 to 2% at temperatures of up to 600°C. The results show that the homogenized models have a good ability to approximate the thermal behavior observed in simulations with discrete fibers, with significant computational savings.