Torsten Höglund

Shear buckling resistance of steel and aluminium plate girders

Abstract During the development of Eurocode 9 for aluminium alloy structures a number of design methods for the shear buckling resistance of plate girders were appraised, by comparison with experimental data. Among studied methods the so-called rotated stress field method [Hoglund, T., Design of thin plate I girders in shear and bending with special reference to web buckling. Royal Institute of Technology, Department of Building Statics & Structural Engineering, Stockholm, 1972], with some modifications, was found to give the best agreement with 366 tests on steel plate girders as well as 93 tests on aluminium alloy plate girders in shear. The method is simple to use and is applicable to unstiffened, transversally and longitudinally stiffened and trapezoidally corrugated webs. This paper presents the rotated stress field method and summarizes the result of the comparisons, including the design methods in Eurocode 3, Part 1.1, version April 1992, for steel plate girders. The rotated stress field method is also adopted in Eurocode 3, Part 1.5: plated structures, draft July 1996.

Slotted steel studs to reduce thermal bridges in insulated walls

Abstract The development of the slotted steel stud made it possible to use steel in external walls in countries with cold climate, like Sweden. By slotting the web the thermal bridges are significantly reduced. Several fabricators of lightweight constructions in Scandinavia now have slotted studs in their range, intended for load-bearing external walls in single family houses and for infill walls in blocks of flats. The development of the slotted stud has also led to the development of the building system for residential called Light Steel Framing. This paper mainly considers design methods for slotted steel studs for external walls. The importance of the slotted stud for the Light Steel Framing System is lighten up by a description of building components as exterior walls, interior walls and light weight floor structures. The thermal properties, sound insulation, springiness and vibrations, fire proof are described as well as building services, architecture, planning and production.

Aluminium in bridge decks and in a new military bridge in Sweden

In this paper, two different types of aluminium bridges in Sweden have been discussed: – aluminium extrusion deck system for rehabilitation of road bridges, and; – a military bridge for the armoured vehicle launched bridge system.

Static design of aluminium structures

This paper shows how the effective thickness concept is used in Eurocode 9 (prEN 1999-1-1 Design of aluminium structures, general structural rules [1]) to allow for local buck ling as well as strength reduction in the heat affected zone (HAZ) of welded members.

Local Buckling of Steel Bridge Girder Webs during Launching

When launching steel-concrete bridges two or more rollers are used at the support. In this paper some tests on girders with two concentrated loads are presented. Comparison with existing formulas showes that two loads can be considered as one load distributed over the distance between the rollers.

EC9 Second Generation: Proposal for New Imperfection Factors for Unstiffened Aluminium Shells

The paper summarizes a part of the activity currently carried out by the CEN/TC250 SC9 Committee, which is presently engaged in setting up the “Second Generation” of EC9 on aluminium structures. In particular, new expressions of imperfection reductions factors α for unstiffened shells are proposed. The new formulation, which is calibrated on the basis of simulation buckling data available in literature, corrects a small issue of the previous one, giving at the same time more reliable and consistent results.

Bearing length on cold-formed sections

The effective bearing length of trapezoidal sheeting on cold formed sections at inner supports is 10 mm according to EN 1999-1-4 (aluminium) and EN 1993-1-3 (steel). In the original design provisions the effective bearing length on Z-sections was the actual width of the loaded flange. In order to find out the appropriate effective bearing length, FEM calculations were made on simply supported beams with C-, Z-and Sigma-cross-section. Contact elements between the trough of the trapezoidal sheeting and the loaded flange of the beam made it possible to evaluate the contact area. This area and the stresses in the trapezoidal sheeting show that the effective bearing length is very small for C-sections. For Z-sections and for Sigma sections with large folds in the web the contact area is the flange width, unless the flange width versus profile height is large and the plate thickness is small.

A Simple Method for the Design of Aluminium Structures

Deflections at the serviceability limit state are often decisive in the design of aluminium structures due to the low elastic modulus. Where design is based on deflections, it may not be necessary to calculate the resistance exactly and simple conservative methods are sufficient. The proposed method may be used to generate a quick, approximate and safe solution, perhaps for the purpose of initial member sizing, with the opportunity to refine the calculation for final design. Another reason for the simple method is enhancing ease of use of Eurocode 9.The principal of the proposed method is to eliminate calculation of effective cross-sections by reducing the elastic resistance with the reduction factor for the most slender part of the cross-section or the factor for HAZ softening whichever is less. This means that you don’t need to define the cross-section class. The disadvantage is that you don’t utilize the plastic reserve for class 1 and 2 cross-sections, nor the redistribution of stresses in the post-buckling range of class 4 cross-sections or sections with HAZ. The procedure is similar to the method with permissible stresses familiar to most engineers.

A unified method for the design of steel beam‐columns

In Eurocode 3, Part 1-1 [1] two methods are given for the design of beam-columns. They have been criticized for their complexity. Furthermore, internal plastic redistribution of stresses of class 3 cross-sections is not utilized in the code. These shortcomings were resolved in proposal for amended rules in [5], however, the procedures for beam-columns are still complicated and difficult to understand. An approximate method for the design of beam-columns was proposed 1968 in [6] which was addressed in the Commentary to the Swedish regulations for steel structures [10] and used in Sweden since then [11]. It was accepted also in Eurocode 9 for aluminium [4], where it is especially convenient to allow for softening of the material at local transverse welds, see [9]. The method is here proposed to be included also in Eurocode 3. In this paper the resistance of class 3 cross-sections is discussed and the unified method for beam-columns is presented. Four worked examples are presented, three of them on rather complicated structures, to show the capability to treat such structures as well.

Resistance of Plated Structures

The design of plated structures involves check of local buckling as well as distorsional buckling of stiffened plates. Local buckling behavior of cross section elements is discussed in section 1. Depending on the width to thickness ratio, the behavior is different, which is considered for in Eurocode 9 by introducing cross section classes. Especially slender webs are treated. In section 2 thin-walled girders in bending are treated and in section 3 stiffened plates in compression. Section 4 deals with orthtropic plates. In section 5 the shear buckling resistance of plate girders with webs without intermediate stiffeners, webs with transversal and longitudinal stiffeners and trapezoidal corrugated webs are discussed. The design rules in Eurocode 9 and some background information are given.