Evaluation of the Internal Forces in a Plane Steel Frame under Fire Situation

Resumo

The study of the high temperature effects on the steel structure systems analysis has been usual. The
structural behavior under fire is an important part of fire protection engineering and the high degree of complexity
and cost of experimental analyses under fire is remarkable. Thus, numerical analysis has been a widely used tool
for investigating the structural behavior in fire. In this context, the present study has as objective to evaluate the
behavior of the internal forces of a double steel frame, submitted to the action of fire. The temperature field in the
cross-section of the structural elements that makes up the frame is obtained by the simplified method of NBR
14323 without thermal protection. Once the temperature of the structural elements is established, the behavior of
the internal forces as a function of the temperature increase is evaluated using the Ftool software. Additionally, an
analysis considering five different scenarios of exposure to fire is performed. The results showed that the
magnitude of the internal forces increases with increasing temperature, which contributes to the loss of structural
strength and, depending on how the fire reaches the structural elements, there is a significant difference in these
forces.