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As part of the ongoing revision of the Eurocodes, design provisions in EN 1999-1-1 on the buckling of longitudinally welded aluminium compression members have been subjected to a critical review. The numerical investigations described in part 1 of the paper were conducted because a need for improvement was identified. In part 2 of the paper, the main observations are presented in qualitative terms. Those observations are: the influence of the allocation of the materials to buckling classes, the influence of the imperfections plus the cross-section geometry including the position and size of the HAZ within the cross-section. Part 3 will conclude this paper by discussing the proposed design approaches in detail.

Underpressure in a tank with a fixed roof may arise in the final stage of its construction as well as during its usage. After completing the construction, when the tank is empty and all manholes and valves, through which air could get into the tank, are tightly closed, underpressure may arise in the case of a sudden change in the weather (air pressure and temperature), which is particularly dangerous in spring or summer. When the tank is in use, underpressure may arise if breather valves are obstructed, e.g. covered by snow during pumping out a product stored in the tank. Underpressure may cause extensive deformations of the shell or the roof of the tank. However, the shell undergoes deformation more frequently, since the roof has a stiff supporting structure.
This article presents stages of deformations of the tank shell and their development from the occurrence of the first deformation to either removal of the causes of underpressure or cracking of the steel shell and thus automatic equalization of pressure inside the tank with atmospheric pressure.

Elastomeric bearings for seismic isolation applications can be subjected to tensile loads depending on the geometrical configuration, high vertical seismic motion or excessive horizontal deformation due to the elongated-period horizontal motion. It is a known fact that cavities develop within elastomeric material when it undergoes a certain amount of tensile force in a very constrained condition since a high hydrostatic tensile stress builds up. Once these cavities have developed, the tensile stiffness of the bearing drops dramatically. This paper contributes to understanding this phenomenon itself and its influence on the basic properties of elastomeric bearings. For this purpose, two types of elastomeric bearing were tested and the cavitation phenomenon observed. Moreover, those test results are compared with the FE simulation results from the modified hyperelastic material model with the cavity damage criterion. The two-phase softening model presented here can simulate the real softening behaviour of elastomeric bearings well, and it may even help us grasp a better insight into the cavitation phenomenon.

European standard EN 1993-1-5 provides the effective width method and the reduced stress method as calculation methods for plate buckling assessment. This article focuses on the reduced stress method, for which the global slenderness concept was introduced into EN 1993-1-5. The concept offers advantages associated with today’s numerical procedures which allow the elastic critical load factor of the full stress field to be determined in a single step, thus taking interaction into account in a very elaborate way. However, this article shows that the interaction verification in its pure format based on the von Mises yield criterion is not able to represent the actual mechanical behaviour of biaxially compressed plates. A simple modification is proposed which leads to appropriate and plausible results.

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The Centner Footbridge at Verviers, Belgium, is a successful design and artifact that links structural optimization and digital steel plate cutting techniques. This steel structure is designed as a statically determinate beam and has a U-profile in cross-section. The webs serving as the safety barriers are assembled from 10 different steel plates that exhibit a laser-cut aperture pattern. The aperture pattern and the steel plate thicknesses have been structurally optimized to deal with the maximum shear forces that occur. For construction purposes, the numerical FE analysis model was translated into a graphic digital model that serves as input data for the steel laser cutter. Once the laser has cut the aperture pattern, the plates are welded together and finished in the fabricator's workshop. The bridge was transported in one piece and installed overnight on site. Recently, the concept of the aperture patterned steel plates has also been successfully applied to other winning design projects. These designs demonstrate that the innovative link between structural optimization and digital steel cutting techniques offers a new and elegant solution for structural systems with a large variety of spans and shapes.

An ausgewählten Holzwerkstoffen (Buchenfurnier, MDF- und Spanplatten) wurde der Einfluss des Einbringens von Hohlräumen auf die Wärmeleitfähigkeit untersucht. Für die Versuche wurden die Platten in mehreren Lagen geschichtet (Lagendicke je nach Material 2,7 bis 5 mm) und die Aufbauten variiert, wobei Platten mit und ohne Hohlräume verwendet wurden. Um den Einfluss der Wärmestrahlung in den Hohlräumen zu untersuchen, wurden zusätzlich Aluminiumfolien (geringer Emissionsgrad) eingelegt. Es konnte festgestellt werden, dass durch das Einbringen von Hohlräumen (Volumenanteil ca. 46 %) eine Reduzierung der Wärmeleitfähigkeit um bis zu 51 % erreicht wird. Ein zusätzliches Einlegen von Aluminiumfolie quer zur Wärmestromrichtung reduziert die Wärmeleitfähigkeitswerte nochmals wesentlich (bis zu 64 %) aufgrund der stark reduzierten Wärmestrahlung in den Hohlräumen. Dies ist besonders ausgeprägt bei den Aufbauten mit größeren Hohlraumdicken. Um das Potential des Anbringens von Hohlräumen im Holzbauwesen zu nutzen, wurde ein Vorschlag für ein neues Produkt auf Holzbasis präsentiert.

Influence of the air cavities on thermal conductivity of selected wood based materials and their application for building industry.
On selected wood-based materials (beech veneer, MDF and particle board), the influence of inserting air cavities on the thermal conductivity was investigated. For the tests, the particular boards (board thickness: 2.7 to 5 mm according to the material) were layered in multiple layers by varying the assemblies and using boards with and without cavities. Additionally, aluminium foils (low emissivity) were inserted to investigate the influence of heat radiation in the cavities. It can be stated that inserting air cavities (approximately 46 % of core material) results in a reduction of thermal conductivity up to 51 %. An additional insertion of aluminium foils perpendicular to the direction of heat flow reduces the thermal conductivity once more significantly (up to 64 %) due to a strong reduced heat radiation within the cavities. This is particularly pronounced in the constructions with larger air cavity thicknesses. Additionally, a proposal of a new product based on wood has been presented to develop the potential of inserting cavities for timber construction.

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