Cold-formed steel sections are widely used in many applications such as structural frames, scaffolding systems, purlins and storage racks. In particular, cold-formed steel portal frames can be an alternative to conventional hot-rolled steel portal frames for industrial, rural and residential low rise buildings. The advantages of using cold-formed steels include a higher strength-to-weight ratio and reduced material, erection and transportation costs.
Over the past two decades a number of researchers [1] to [3] have undertaken tests on cold-formed steel portal frames. The tests mainly focused on the behaviour of joints, and employed relatively stocky sections. Hence, they provided little insight into the effects of cross-sectional instability on the overall stability of the frame.
In this paper, three portal frame tests are described, the main purpose of which was to study the effect of cross-sectional instability on the two-dimensional sway failure of cold-formed steel. The tests demonstrated significant local and distortional buckling before reaching the ultimate load. Finite element models were calibrated against the tests. The calibrated models therefore can be used for a parametric study to investigate the significance of the additional second-order effects caused by local/distortional bucking. The paper details the tests and the numerical simulations.

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Structural glass corresponds to an innovative material with extraordinary aesthetical and architectonic potential that has undergone significant technological advances in recent years, yielding it stronger and safer. For this reason, the use of structural glass has increased considerably in the last decade and is now an unavoidable presence in most of recent reference buildings.
The structural capacity of glass elements is brought in from reinforcing techniques of different types. One of the possibilities corresponds to pre stressed cables reinforcement. This technique is very effective in terms of resistance and deformability and corresponds to a light reinforcing element rendering the so called spider web effect. In the framework of the research project “S-Glass: Structural performance and design rules of glass beams externally reinforced” [1] study the behavior of laminated glass beams reinforced by too twin external steel rods.
The work presented in the current paper is within the framework of S-Glass project aiming at characterizing the behavior of reinforced laminated glass beams in the non-crack regimen. For this purpose experimental and numerical analysis were prepared. The numerical model was used for a cable layout optimization analysis. Furthermore an analytical solution is put forward, which tackles the beam-cable load transfer indetermination. Final conclusions are established on the bases of a comparison established between experimental, numerical and analytical results.

The accelerating needs of communication have led to many modern railway stations made of steel and glass being built or upgraded all over the world during the last two decades. That trend, influenced by local architectural traditions, is clearly evident in Japan, too. This paper, focusing on that trend, is a continuation of the authors’ previous publication [1].

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This paper reports on recent developments in high-strength and stainless steel tubular members and connections. It includes carbon steel tubes with a yield stress up to 1350 MPa and stainless steel tubes. The paper describes high-strength tubes in terms of residual stresses, material properties at elevated temperatures, member behaviour, welded connections under static loading, fatigue strength of welded connections, fabricated sections utilizing high-strength steel tubes and stainless steel tubular members and connections.

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A review of seismic design solutions for connections is presented in this paper, with particular focus on methods that are already “pre-approved” or “acceptable to code” for use by engineers in steel-framed structures using hollow sections. This review is intended to illustrate the limited options currently available to structural engineers. The survey mainly covers European and North American design solutions, but the latter are also heavily influenced by Japanese practice. The scope includes both braced frame connections (utilizing hollow sections for the bracing members at least) and unbraced frame connections (utilizing hollow section columns), the latter including both rigid and semi-rigid beam-to-hollow section column connections. Dissipative and non-dissipative connection types are considered where appropriate. Emphasis is placed on connection configurations and concepts rather than detailed design information, but references to other sources are given for further details. Areas in which there is a paucity of established design guidance are noted, and the review concludes with recommendations for further research and development regarding specific types of connections to hollow sections subjected to seismic loading.

Drafts of the AISC guide for hotspot stress contained several radical technical proposals that could benefit from exposure and peer review before publication in the design guide. These are:
- S-N slope of -1/3.6 with no transition knee,
- notch stress size effect based on mesh density, and
- thickness-dependent strain limits for TxT meshing.
These proposals are presented here along with their supporting data.

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This paper presents a summary, with background information, of the design recommendations developed recently for axially loaded X and T joints between elliptical hollow sections (EHS). These recommendations are based on experimental tests, finite element (FE) calibration and parametric studies carried out in a collaborative research programme between the universities of Singapore, Toronto and Delft.
The strength equations are presented in a similar manner to those currently adopted for circular hollow section (CHS) joints and rectangular hollow section (RHS) joints in ISO 14346 (2013). The ISO recommendations are based on, and are similar to, those of the International Institute of Welding, IIW-XV-E, which were also published by the Comité International pour le Développement et l’Etude de la Construction Tubulaire (CIDECT) in recent editions of their Design Guides.

Over the last decade, extensive numerical analyses have been conducted on axially loaded uniplanar K gap, T and X joints made of circular hollow sections (CHS), considering a wide range of geometrical parameters and different types of chord load. Based on the large amount of numerical data, in 2007, new joint capacity and chord stress equations were derived for CHS joints. This article presents detailed comparisons made between the (mean) strength equations for K gap joints and the experimental data available. These design equations were first discussed and approved by Sub-commission XV-E of the International Institute of Welding (IIW), subsequently published in the CIDECT Design Guide for CHS joints [1] and adopted in the 3rd edition of the IIW Static Design Procedure for Welded Hollow Section Joints [2], which formed the basis for the ISO 14346 recommendations [3] published recently.

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Cold-formed hollow sections are a widely used tubular construction material. The applicability, weldability and reliability of cold-formed rectangular hollow sections are sometimes questioned because of the consequences of cold forming and inhomogeneous cross-sections. One of the main concerns is related to the cold-formed corner areas and possible loss of toughness due to strain ageing in the vicinity of the welds. Conventional hot-rolled C-Mn steels are susceptible to strain ageing, and Eurocode 3 includes restrictions on welding in the cold-formed corner area. Both steelmaking and hot rolling have undergone crucial developments and this has had an impact on cold-formed hollow sections. Thermomechanically rolled fine-grain steels became state of the art at the end of the 1990s. This study confirms that cold-formed EN 10219 hollow sections made of suitable fine-grain steels have a similar Charpy-V toughness on the flat face and in the corner, and that even after ageing the transition temperature T40J in the corner area is at a very low level, typically below -50 °C. The load and deformation capacities of X- and K-joints fulfil the requirements without any noticeable ageing effects. The advances in steelmaking and hot rolling enable the manufacturing of reliable and versatile cold-formed EN 10219 hollow sections for welded structures with good low-temperature ductility even in the cold-formed corner area.

The costs of the self-weight of a structure have never been a real issue in the design of steel girders, since the material costs of a structural element are mainly determined by labour costs. The booming economies of China and India cause a continuously increasing demand for steel. This and the now stringent regulations regarding sustainability make material economy in design much more interesting.
In a material economy-driven plate girder design, the lever arm between the flanges will increase. This leads to a higher stiffness and bending moment resistance, but also to an increase in the web slenderness of the girder. This means that high-strength steels can be used, leading to a large reduction in steel consumption.
Eurocode 3, EN-1993-1-5, [1] restricts the web slenderness based on the formula to avoid flange-induced buckling, originally derived by Basler [2]. However, experimental and theoretical research conducted on 10 unstiffened plate girders with high web slenderness ratios at the Stevin II Laboratory of Delft University of Technology shows that this formula is too conservative.
This paper presents the results of this research and suggestions for a new plate girder design strategy.

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The current version of the Eurocode for the design of joints does not include any brace load capacity reduction for welded hollow section joints with tensile chord preloading as opposed to those without. However, the more recent 2nd edition of the CIDECT design guides or the ISO standard for welded hollow section joints includes a strength reduction due to tensile chord stresses. This paper presents the results of experimental and numerical investigations into how tensile chord stresses influence the capacity of circular hollow section X-joints. The conclusion of this study is a new chord load function proposal for circular hollow section joints subjected to tensile chord stresses.

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Steel tubes may be loaded by concentrated lateral loads such as support or impact loads. Impact loading, for example, is an important load case for buried pipelines that are struck during excavation activities, or large-diameter tubes during transportation (handling accidents). This paper presents an analytical model based on shell theory to determine the elastic-plastic load deformation behaviour. Test results are given as well as the results of finite element calculations. The finite element results and the model equations are in good agreement with the experimental results and illustrate the tube denting response.

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Lazika is a new city in Georgia located on the Black Sea coast. The one-hundred meter long Lazika Pier with its 31 m high landmark sculpture is one of the first structures to mark the beginning of the development of this new metropolis.
The sculpture designed by German architect Jürgen Mayer H. consists of stacked oval elements - so called blobs - organized in seven levels. The blobs are subdivided into vertical plain levels running in an orthogonal direction with a distance of 90 cm. Due to the exposed position, tough requirements concerning corrosion resistance and a pretty tight timetable for design, fabrication and erection, structural steel has been chosen as the building material. The sculpture consists of steel plates with varying thicknesses of 5 to 10 mm. Elements composed of plasma-cut plates were pre-fabricated within a site workshop and installed using mobile cranes. Exterior and interior lighting features provide a dynamic and pulsating look to the sculpture.