Análise da confiabilidade estrutural de uma viga de madeira otimizada e não otimizada submetida a curva de incêndio natural parametrizada - método das propriedades reduzidas

Abstract

Wooden structures, when designed for fire scenarios, tend to be more robust to ensure the desired structural reliability. However, structural optimization seeks to minimize material usage to the necessary extent, aiming for resource efficiency. This process, however, does not always clearly demonstrate the safety level of the structure after minimization. Structural reliability theory allows for the quantification of this safety level through probabilistic models, which simulate different conditions and can calculate the failure probability of optimized or nonoptimized structures. Based on this concept, the present study investigates a wooden beam subjected to a natural fire model, aiming to optimize its cross-section and evaluate failure probabilities for different fire exposure times. For this purpose, Monte Carlo Simulation and the First Order Reliability Method (FORM) were employed, considering a beam with three fireexposed faces. Structural optimization was performed using the reduced properties method, in accordance with Eurocode 5. The results indicate that optimization enhances the beam's structural integrity during fire exposure, particularly by increasing its height to improve bending resistance. Furthermore, the optimized beam exhibited a lower failure probability compared to the non-optimized version, both under normal conditions and fire exposure. The analyses also demonstrate that the variable load is the most influential factor in failure probability.These findings highlight the importance of considering the interplay between reliability and optimization in the design of fire-exposed wooden structures, providing a more comprehensive approach to simultaneously ensuring safety and economic efficiency.