Plastic-hinge approach for inelastic analysis of steel–concrete framed structures

Inelastic analysis of semi-rigid composite structures under fire conditions

“…A second-order refined plastic hinge analysis method, used to assess the performance of steel and composite (steel-concrete) structures under fire conditions, previously validated for continuous frames (Landesmann, 2010), is presented in this paper for semi-rigid connections. The computational approach, SAAFE Program (Landesmann et al, 2009), has been developed based on the Advanced Analysis concept (Chen et al, 1996), taking into account the non-linear behavior of material at elevated temperatures, as recommended by part 1.2 of Eurocode 4 (EC4-1.2, 2003).…”

“…The proposed two-dimensional plastic-hinge model considers the following characteristics to be discussed in the presented section (Chen et al, 1996;Liew et al, 2002;Landesmann, 2010): (i) distributed plasticity effects described by a stiffness parameter η, evaluated as a function of the yielding progress at each plastic-hinge location, (ii) an approximate scheme based on an effective tangentmodulus E t concept, which reduces the modulus of elasticity in the element stiffness calculation, considering both the residual stress and out-of-straightness effects, and (iii) a second-order formulation based on conventional stability functions allowing an accurate identification of member instability with low computational efforts. The following assumptions are made for the stiffness formulation of the present approach: (i) the members are prismatic and slender in which the Bernoulli-Euler hypothesis is valid, (ii) lateral-torsional buckling, twisting effect, warping and shear deformations are neglected, (iii) nodal load response is only included in the present formulation, (iv) capacity of concrete under tension is negligible, (v) no separation between steel beam and concrete is allowed, and (vi) element is elastic and all material nonlinearities are allowed for in a plastic-hinge spring.…”

“…The inelastic reduction factor η concept, which represents the ratio between inelastic and elastic flexural stiffness (Chen et al, 1996), derived for composite structures under fire conditions (Landesmann, 2010) is given as follows (Eq. (2)), where (EI el ) is the elastic flexural stiffness.…”

“…This paper is addressed to the development of an inelastic hingebased numerical tool, denoted as SAAFE Program (System for Advanced Analysis for Fire Engineering), able to perform material and geometric non-linearity analysis of 2D semi-rigid steel-concrete composite framed structures under fire conditions. The proposed plastic-hinge model, which has been previously implemented and validated for "rigid" composite framed structures (Landesmann et al, 2009;Landesmann, 2010) is adapted herein to assorted semirigid connections configurations under fire. The presented model is derived from inelastic moment-curvature-temperature-thrust response of composite elements under fire, representing a smooth transition from initial yield to full plastic domain under the interaction of axial and bending effects (Iu et al, 2007(Iu et al, , 2009).…”

Detailed three - dimensional nonlinear hybrid simulation for the analysis of large - scale reinforced concrete structures

“…Through his paper, Landesmann [65] (2010) presented an application of a computational tool, named SAAFE Program, developed to analyze nonlinear inelastic steel and composite 2D framed structures. The proposed plastic-hinge model was formulated based on three characteristics which controlled the beam stiffness, the residual stresses and the structural member instability.…”