Evaluation of Internal Forces in Cold-Formed Steel Truss exposed to Fire

Resumo

The use of cold-formed steel structural elements is evident in recent decades and motivated by their
structural efficiency as a function of the relationship between strength and weight. Its application is wide ranging
in buildings or hangars. However, due to the slenderness of the elements, projects involving cold-formed steel
are governed by the instability phenomena. In a fire situation, it is known that the physical and mechanical
characteristics of materials deteriorate during exposure to fire and the resistant capacity decreases with
increasing temperature. Thus, this work aims to analyze a truss subjected to the action of fire. The CS-ASA/FA
program defines the temperature field of the cold-formed steel cross-sections without fire protection and the
simplified method of NBR 14323 is used to obtain the temperature in the truss section with hollow encasement
fire protection material. Additionally, the behavior of normal force on the most requested bar due to temperature
increase is evaluated. The results showed the importance of using fire protection material in reducing the
temperature of steel elements and showed that the magnitude of normal force increases with increasing
temperature, which contributes to the loss of structural strength.