This work aims at investigating the BUCKLING behaviour of cold-formed steel (CFS) lipped channel (LC) beams undergoing local (L) -DISTORTIONAL (D) -lateral-torsional (LT) BUCKLING mode interaction for the sake of developing an analytical model to calculate the ultimate resistance to bending moment. The section geometries are identified to have nearly equal elastic local, DISTORTIONAL and lateral-torsional BUCKLING moment values by performing elastic BUCKLING analysis. The identified sections satisfy the condition for prequalified sections in AISI-S100-2007. A finite-element model has been developed and verified against the available test data for cold-formed steel lipped channel sections subjected to the major axis bending. Parametric studies were carried out to investigate the influence of geometries and yield stress values. The numerical results are compared with design predictions from the Direct Strength Method (DSM) in North American specifications for cold-formed steel structures. Based on the comparisons, design recommendations are introduced for cold-formed steel lipped channel beams which experiencing local/DISTORTIONAL/lateral-torsional BUCKLING mode interaction.

The aim of the study is to investigate the DISTORTIONAL BUCKLING behaviour of intermediate cold-formed lipped channel sectionunder pinned end condition subjected to axial compression. An extensive test and numerical investigation of cold-formedlipped channel column with various types of intermediate web stiffeners is presented. In this study, three types of intermediateweb stiffeners are chosen such as V, U and Σ . The entire cross-sectional dimensions meet with the pre-qualified columndimension given in Direct Strength Method for cold-formed steel structures. Totally, 12 columns are tested and results arecompared with the numerical analysis. Numerical analysis is carried out using software ABAQUS. Material and geometricimperfections are incorporated in the FE model. Selected section dimensions met with the DISTORTIONAL BUCKLING mode. Goodcorrelation is achieved between experiment and finite element analysis. All the results are compared with the Direct StrengthMethod specifications for cold-formed steel structures. Based on the comparison of results, a suitable design modification isproposed. Furthermore, results are verified with the existing results which are available from the literature.

Composite steel/concrete beams may buckle in hogging bending regions. As the top flange of I-beam in that arrangement is restricted from any translational deformation and twist, the web will distort during BUCKLING presenting a phenomenon often described as restricted DISTORTIONAL BUCKLING. There are limited studies available in the literature of restricted DISTORTIONAL BUCKLING of composite steel/concrete I-beams subjected to negative or hogging bending. There is none however that includes the effect of partial shear interaction. In this paper, finite element models for in-plane analysis and out-of-plane BUCKLING of continuous composite I-beams including the effects of partial shear interaction are presented.

In this paper, the lateral-torsional and DISTORTIONAL BUCKLING stability of rafters with elastic supports subjected to gravity loads have been studied by means of a numerical method. To fulfill this purpose, the equilibrium equations for elastic rafter members with linear behavior are derived from the stationary condition of the total potential energy. In the applied energy method, effects of initial stresses and load eccentricities from centroid of cold-formed cross-sections are also considered. The Power series expansions are utilized to solve the fourth-order differential equations of considered rafters with variable coefficients. According to aforementioned method, displacements components and geometric properties are approximated by power series form with a known degree. The critical BUCKLING loads are then derived by solving the eigenvalue problem. In order to present the accuracy of the proposed method, several numerical examples including lateral-torsional behavior and DISTORTIONAL BUCKLING analysis of rafters with cold-form sections are considered. The evaluated results are compared to the finite element simulations and other available methods.

A linear and non-linear bubble finite strip method of analysis is used to study the local, DISTORTIONAL and lateral BUCKLING monosymmetric I-beams under pure bending. The variation of local BUCKLING coefficients of flanges and web of the sections are obtained for different beam geometries. The method is deployed to investigate the elastic local BUCKLING of monosymmetric I-sections in bending containing a longitudinal stiffener attached to the web. The optimum position of this stiffener is calculated to maximize the web local BUCKLING stress. The non-linear finite strip method is then used to study post-local BUCKLING behavior of imperfect monosymmetric I-sections under bending.

This work aims to study the effect of connector interaction in behaviour and ultimate strength of intermediate length CFS open sections under axial compression. A stiffened channel section is considered for the study it included a total of 6 structural tests. Finite element models were developed using ANSYS including geometric and material non linearities. The numerical results were validated on the basis of the test results and both has good agreement with each other. An extensive parametric study on the influence of depth and spacing of connectors was carried out using this finite element procedure. The strength predicted by the finite element model and tested specimens of open sections were compared with the design strength calculated using the DSM–AISI 100: 2007, AS/NZS: 4600-2005 and IS: 801-1975. Recommendations concerning the design of the section with connectors are given based on the results.

This paper presents a new control method for a three-phase four-wire Unified Power Quality Conditioner (UPQC) to deal with the problems of power quality under DISTORTIONAL and unbalanced load conditions. The proposed control approach is the combination of instantaneous power theory and Synchronous Reference Frame (SRF) theory which is optimized by using a self-tuning filter (STF) and without using load or filter currents measurement. In this approach, load and source voltages are used to generate the reference voltages of series active power filter (APF) and source currents are used to generate the reference currents of shunt APF. Therefore, the number of current measurements is reduced and system performance is improved. The performance of proposed control system is tested for cases of power factor correction, reducing source neutral current, load balancing and current and voltage harmonics in a three-phase four-wire system for DISTORTIONAL and unbalanced loads. Results obtained through MATLAB/SIMULINK software show the effectiveness of proposed control technique in comparison to the conventional p-q method.