Abstract
Abstract The inelastic second-order behavior of steel structural columns under minor-axis bending is presented in this article. To study this behavior, a nonlinear frame element formulation is adopted in which the steel's plasticity process is accompanied at the nodal points of each finite element through the refined plastic-hinge method (RPHM). A tangent modulus approach is employed in order to consider the stiffness degradation in function of the internal forces' variation, and the second-order effects, residual stresses and geometric imperfections are considered in the modeling of column behavior. As a criterium for defining the ultimate limit state of the column cross-section, strength surfaces are adopted. These surfaces describe the interaction between the axial force and bending moment (N-M interaction diagrams). To solve the nonlinear equilibrium equation for the structural system, the Newton-Raphson method is used, coupled with continuation strategies. Columns with different slenderness, boundary and loading conditions are analyzed, and the results obtained are comparable to those found by other researchers. The results lead to the conclusion that the numerical approach adopted in this study can be used for a better behavioral understanding of the steel column under weak-axis bending.
Highlights
Nowadays, steel material is commonly employed in civil construction
In the plastic zone method (PZM) (Clarke, 1994; Alvarenga, 2010), the cross-section of each finite element is discretized in fibers and the second order effects and residual stresses can be directly considered in the analysis
The tangent modulus Et3 furnished conservative curves for all of the situations related to the analytical solutions, and it is more precise when compared to the solutions by Zubidan (2011), who used the PZM
Summary
Steel material is commonly employed in civil construction. Besides being a completely recyclable material, steel has important characteristics such as strength and durability, good ductility and speedy manufacturing and assembly times. In the PZM (Clarke, 1994; Alvarenga, 2010), the cross-section of each finite element is discretized in fibers and the second order effects and residual stresses can be directly considered in the analysis. To achieve the proposed objective, the tangent modulus equation suggested by Ziemian and McGuire (2002) is implemented in the CS ASA (Computational System for Advanced Structural Analysis; Silva, 2009) In this equation, the cross-section stiffness degradation varies in function of the axial force and bending moment around the minor axis. The numerical formulation proposed employs the strength surfaces (McGuire et al, 2000; BS 5950, 2000), adequately evaluating the interaction between the axial force and bending moment at the minor axis Validation of these strategies is made by analysis of the columns under various boundaries, slenderness and loading conditions.
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