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This paper compiles the experimental and finite-element parametric study on member distortional buckling behaviour of new built-up metal hybrid double-I-box beams (HDIBBs). The cross-section of this built-up beam is unique and looks similar to the shape of a double-I-box fabricated using four channel sections. The flange plates were provided with an intermediate stiffener. In these built-up beams there is more material in the flange portions far away from the horizontal centroidal axis of their cross-section. Hence, there is an increase in the flexural rigidity that enhances the moment capacity of the beam, under major axis bending. The geometry consists of torsionally rigid closed-box web portion that provides high resistance to minor axis lateral-buckling. The varying parameters considered were the ratio of yield stresses of the flange to the web steel plates, the ratio of breadth to the depth of the section, and the flange plate thickness. In the experimental programme, all the HDIBB members failed due to kinds of distortional buckling which was identified by web buckling and flange twist along edges. The results revealed that when flange plate slenderness increases there is a drop in the moment resistance capacity of the beams. The numerical study was performed using ABAQUS software. In comparison, there was good agreement between experimental and numerical results. The validated finite element models were further extended to perform parametric studies on ideal HDIBB models. Both the experimental and parametric study results were compared with the predicted strengths using effective width method equations specified in the Euro code standards EN 3-1-3. It was found that the current Euro code design rules slightly over-estimate the distortional buckling resistance capacity of closed form built-up cold-formed steel members. A new design equation was formulated and recommended for estimating the reduction in distortional buckling moment resistance capacity for HDIBBs. [ABSTRACT FROM AUTHOR]

This paper describes a subassemblage seismic test program performed on six buckling-restrained braces (BRBs). Two different brace core segment lengths and two different buckling-restraining mechanisms were examined. The applied loading histories included a qualifying quasi-static cyclic test with stepwise incremental displacement amplitudes and a dynamically applied seismic loading. A test was also carried out on a conventional bracing member for comparison purposes. The concrete-filled tube specimens exhibited satisfactory performance under the quasi-static loading protocol, regardless of the length of the core segment. Strain hardening and frictional responses resulted in brace axial forces significantly exceeding the core yield capacity. The steel BRB system exhibited good performance under the quasi-static and dynamic loading sequences, provided that the clearance between the brace core and the buckling-restrained mechanism was kept to a minimum. The dynamic loading protocol was less severe for low-cycle fatigue than the quasi-static loading, but higher strain rates resulted in amplified yield resistance. The conventional bracing member withstood the entire quasi-static loading history but exhibited limited energy-dissipation capacity compared with the concrete-filled BRBs. [ABSTRACT FROM AUTHOR]

The effects of geometrical imperfections on the critical load of elastic cylindrical shells when subjected to axial compression are studied through analytical modelling. In addition to distributed defects of both axisymmetric or asymmetric forms, emphasis is put on the more severe case of localized defects satisfying the axial symmetry. The Von Kármán – Donnell shell equations were used. The obtained results show that shell strength at buckling varies very much with the defect amplitude. These variations are not monotonic in general. They indicate however a clear reduction of the shell critical load for some defects revealed as the most dangerous ones. The proposed method does not consider the complete coupled situation that may arise from interactions between several localized defects. It facilitates nevertheless straightforward initializing of closer analyses if such couplings are to be taken into account by means of special numerical approaches, because it enables fast a priori selection of the most hazardous isolated defects. [ABSTRACT FROM AUTHOR]

A numerical investigation of the monotonic and cyclic behaviour of steel gusset plate connections is conducted using a nonlinear finite element model. Successive versions of the model, which include the effects of framing member stiffness, nonlinear material behaviour, initial imperfections, and bolt slip, are formulated and validated by comparison with test results. A parametric study is then conducted to examine the effects of the load sequence and the interaction between the gusset plate and the brace member under cyclic loading. This investigation demonstrates that the cyclic behaviour of gusset plate connections can be modelled accurately using a simplified finite element model. Gusset plate – brace member subassemblies, wherein the gusset plate is designed as the weak element in compression rather than the brace member, are shown to have stable behaviour under cyclic loading and better energy absorption characteristics than similar subassemblies with the brace member designed as the weak element in compression. [ABSTRACT FROM AUTHOR]

The distributed Brillouin sensor (DBS) was used to monitor the structural changes in a steel pipe and a composite column subjected to heavy loads. The column was made of concrete reinforced with fibre-reinforced-polymer (FRP) rods and sheets. The test reproduced earthquake-like conditions. The pipe had a length of 2.58 m and diameter of 0.75 m. The DBS measured the strain distribution in both the concrete column and the pipe under various loads. The DBS provided detailed information on the structure's health at the local and global level, before any deformation, cracks, or buckling was visible. This work demonstrates that the DBS is capable of extracting critical information useful to engineers: the engineer's experience and judgement, in conjunction with appropriate data-processing methods, make it possible to anticipate structural failures. The DBS is a promising tool for structural health monitoring. [ABSTRACT FROM AUTHOR]

A generalized numerical method is proposed to derive the static and dynamic stiffness matrices and to handle the nodal load vector for static analysis of non-uniform Timoshenko beam–columns under several effects. This method presents a unified approach based on effective utilization of the Mohr method and focuses on the following arbitrarily variable characteristics: geometrical properties, bending and shear deformations, transverse and rotatory inertia of mass, distributed and (or) concentrated axial and (or) transverse loads, and Winkler foundation modulus and shear foundation modulus. A successive iterative algorithm is developed to comprise all these characteristics systematically. The algorithm enables a non-uniform Timoshenko beam–column to be regarded as a substructure. This provides an important advantage to incorporate all the variable characteristics based on the substructure. The buckling load and fundamental natural frequency of a substructure subjected to the cited effects are also assessed. Numerical examples confirm the efficiency of the numerical method. [ABSTRACT FROM AUTHOR]