Modeling of the Thermo-Elastoplastic Behavior of Space Trusses

Abstract

Space trusses are structures composed of rods usually metalics (steel or aluminum) that are used mainly to sustain the roof of large spans present in sheds and pavilions. The present work has the aim of computationally modeling the coupled thermo-elastoplastic behavior in space trusses under large displacementsandlargestrains. The present approach uses the heat transfer equation and an elastoplastic constitutive model, modified to include the thermal influence. Computer simulations of the resulting mathematical model can be used for the development of structural projects under large variations of temperature, as occurs in fire situations. The finite element method (FEM) was used to determine the temperature field in transversal section of rods. In order to find the displacements and strains in rods due to thermal variation and loadings, it was used the direct stiffness method. The Newton-Raphson method was used to solve the non-linear equilibrium equations of the thermomecanic constitutive model. The developed code was aplied to simulate a truss under a simplified standard fire situation, where the high temperature causes a decrease in the resistance and stiffness of the rods, which may plastificate and fail in a short time of exposure.