Inelastic large deflection analysis of space steel frames including H-shaped cross sectional members

This paper presents an efficient inelastic and large deflection analysis of space frames using spread of plasticity method. New accurate formulae are proposed to describe the plastic strength surface for steel wide-flange cross sections under axial force and biaxial bending moments. Moreover, empirical formulae are developed to predict the tangent modulus for cross sections under the combined forces. The tangent modulus formulae are extended to evaluate the secant stiffness that is used for internal force recovering. The formulae are derived for steel sections considering the residual stresses as recommended by European Convention for Construction Steelwork (ECCS). A finite element program based on stiffness matrix method is prepared to predict the inelastic large deflection behavior of space frames using the derived formulae. The finite element model exhibits good correlations when compared with the fiber model results as well as previous accurate models. The analysis results indicate that the new model is accurate and computational efficient.