Flexural behaviour of hot-finished high strength steel square and rectangular hollow sections

High strength steels, considered in the context of the structural Eurocodes, as steels with a yield strength over 460 MPa, are gaining increasing attention from structural engineers and researchers owing to their potential to enable lighter and more economic structures. This paper focuses on the bending strength of hot-finished high strength steel (HSS) square and rectangular hollow sections; the results of detailed experimental and numerical studies are presented and structural design rules for HSS cross-sections are proposed. A total of 22 in-plane bending tests, in three-point bending and four-point bending configurations, on HSS sections in grades S460 and S690 were conducted. The experimental results were replicated by means of non-linear finite element modelling. Upon validation of the finite element models, parametric studies were performed to assess the structural response of HSS sections over a wider range of cross-section slenderness, cross-section aspect ratio and moment gradient. The experimental results combined with the obtained numerical results were used to assess the suitability of the current European (EN 1993-1-1 and EN 1993-1-12) cross-section classification limits for HSS structural components. The reliability of the proposed cross-section classification limits was verified by means of the EN 1990 - Annex D method.The Research Fund for Coal and Steel (RFCS) under grant agreement No. RFSR CT 2012-00028. V&M DEUTSCHLAND GMBH, Mr. Gordon Herbert, Mr. Fillip Kirazov and Mr. Isaak Vryzidi

Detailing of I-beam-to-CHS column joints with external diaphragm plates for seismic actions

In this paper monotonic and cyclic finite element (FE) analyses are presented for the development of an I-beam-to-CHS column steel moment joint for seismic actions. The development process for the final joint details includes: (1) eliminating two identified structural deficiencies of distortion in column web panel and strain concentrations in the external diaphragms; (2) creating a multi-fuse energy dissipation mechanism; (3) devising a joint to delay onset of beam yielding. Two external diaphragm collar plates are welded to the circumference of the CHS column for connection to beam flanges. Various collar ring widths are examined for these horizontal diaphragms and a width (based on achieving full strength of the beam flanges) is found to produce an acceptable web panel performance. Different types of stiffener geometries in the connection region are then trialed to eliminate strain concentrations in the diaphragms. Two pairs of triangular diaphragm stiffeners are found to provide the desired performance. In order to produce a multi-fuse energy dissipation mechanism, tapered cover plates (TCPs) equipped with vertical stiffeners (VSs) are integrated into the joint. Oversized web holes of 4–10 mm are required to enable inelastic deformation for an overall joint rotation of 60–100 mrad, without undesirable web distortion. Further FE analyses are used to design the TCPs and VSs so they can be replaceable link post-seismic actions. For the final joint detailing it is shown that 6 mm oversized holes for the TCPs will delay the occurrence of yielding in the beam until the joint rotation is 70 mrad

Hysteretic Analysis of Steel Plate Shear Walls (SPSWs) and a Modified Strip Model for SPSWs

Steel plate shear walls (SPSWs) have become more and more popular in recent years because of their potential huge energy dissipation capacity and ductility under lateral loads. Due to their low cost and fast construction, SPSWs have potential application in practice. The finite element software ANSYS applied to the analysis of the hysteretic behavior of SPSWs is described in this paper first. It was found that compressive stress existed in SPSWs and the effects became more evident with decreasing height-to-thickness ratio. This was validated by comparing theoretical and experimental test results. Secondly, based on the analytical results, a modified strip model is proposed. In the modified model, the compressive effects in the panel were taken into account and it was then found that the load-carrying capacity and the energy dissipation capacity agreed well with the already carefully validated experimental results

Experimental study on the rotation capacity of cold-formed steel beams

The rotation capacity of cold-formed steel (CFS) beams has been evaluated through experimental investigation. Studies on different structural levels have been performed. At the element level, different profile slenderness ratios have been considered, and different section shapes have been investigated by increasing the number of flange bends: C-section and curved-section, which represents an infinite number of flange bends. At the connection level, a web bolted moment resistant type of connection using through plate has been adopted. In web bolted connections without out-of-plane stiffeners, premature web buckling results in early loss of strength. Hence, out-of-plane stiffeners have been examined to delay web and flange buckling and to produce relatively high moment strength and ductility. The experimental results have been compared with numerical results obtained by the authors in another paper work. The results revealed that increasing the number of flange bends will not in all cases enhance the behavior. Meanwhile, the use of out-of-plane stiffeners can increase the seismic energy dissipation, the moment strength and the ductility, when compared with the case without stiffeners