Utilização de métodos computacionais na reconstituição de incêndios : aplicação ao caso do shopping total

Abstract

A validação das ferramentas de simulação computacional de incêndio é fundamental para estudar situações de propagação do fogo e para determinar as curvas de elevação de temperatura dos elementos estruturais em cada cenário. Isso permite, identificar riscos e planejar estratégias para proteger as estruturas e seus usuários dos efeitos de incêndios. O presente trabalho reporta uma simulação aproximada da dinâmica de um dos mais importantes incêndios recentes ocorridos na cidade de Porto Alegre, que atingiu o Shopping Total.Os resultados obtidos indicam que as ferramentas de simulação são promissoras, mas que é necessário investir na formação de bancos de dados mais amplos e precisos sobre as características dos materiais encontrados nas edificações, para poder fornecer aos programas informações sobre comportamento de ignição e propriedades em temperatura ambiente e sob aquecimento.

One important line of research of the Laboratory of Structural Tests and Modeling (LEME) from the Federal University of Brazil at Rio Grande do Sul (UFRGS) aims to contribute to the study of structural elements under high temperature exposure typical of fire developments in buildings. This type of research is still scarce in Brazil, mainly due to the high costs of experimental facilities and equipment necessary to conduct laboratory or controlled tests that accurately reproduce real fire conditions. A possible way to overcome this problem is to use computational simulations to estimate boundary conditions on the surface of structural elements during fire situations. One interesting aspect related to the use of computational scenarios is enabling the testing of different hypothesis regarding the dynamics of the blaze, resulting in distinct temperature and smoke flow estimates. However, there is still a lot of uncertainty regarding the accuracy of simulation tools in reproducing real situations, and the validity of the resulting estimates is often questioned. To check if this concern is valid, it is useful to analyze how these tools reproduce known case studies, context in which the present study was conceived.The work attempted to represent, using one of the most modern computer simulation tools (the “Fire Dynamics Simulator” software, from NIST), a fire that occurred in a real structure, in Porto Alegre/RS The case of a commercial Shopping Mall (Shopping Total) was chosen due to availability of data about damage and estimates of temperatures reached in different locations, obtained from a detailed inspection conducted by the LEME team after the event, in order to reconstruct fire dynamics and identifydamaged elements. The paper contains a comparative study of temperature curves in selected structural elements, both estimated by simulationand obtained by testing samples collected after the fire. The results indicate that the use of simulation tools is promising, but highlight the need to invest in the formation of larger and more precise databases about the characteristics of materials found in buildings in order to provide better input information about ignition behavior and properties at room temperature and under heating for the simulation tools to work with. The study made clear that it is necessary to develop better strategies for considering the sharp and sudden deterioration of materials due to spalling, in order to reliably reproduce the behavior of thin slab elements. Several adjustments and adaptations were necessary to obtain a good fit between real structural behavior and the results of the numerical simulations.