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Abstract: General design concept for buckling structures – Suggestion for a new part F of EN 1993‐1‐5. A revised version of EN 1993‐1‐5 should soon be published. The reduced stress method will be reworked in section 10. The complementary regulations published recently in this journal, in particular to the biaxial pressed stiffened steel plate, are partly time‐consuming. In addition to these announced rules a concept with „gradual exactness” with which a low limit value of buckling resistance can be fast determined is applied in the code proposal. A new reduction factor is defined for stiffeners, based on an already published proposal for the geometrical imperfection amplitude. Because of the compatibility to the MNA/LBA concept in EN 1993‐1‐6, the suggestion for a new part F of EN 1993‐1‐5 can be used generally for compound steel structures in future. Examples are given for application of the code proposal. [ABSTRACT FROM AUTHOR]

Experimental investigations on high‐strength CHS for crane‐ and scaffolding construction So far, only a limited amount of experimental results is available for the derivation and verification of design principles for cold‐formed, high‐strength crane and scaffolding tubes up to S960. In this article, the authors present the conduction and results of buckling tests on centrally loaded scaffolding and crane tubes of steel grades up to S960. Measurements of residual stresses as structural imperfections using the sectioning method are discussed on ungalvanized and galvanized CHS in S960. Additionally, the geometric imperfections of the test specimens, which were captured by 3D scanning, are discussed and compared with the approaches of the European buckling curves. The deformations of the test specimens in the buckling tests were recorded using digital image correlation (DIC). The effects of galvanization and the buckling direction on the load‐bearing capacity are highlighted and elucidated. [ABSTRACT FROM AUTHOR]

A mechanically consistent approach for stability verification of timber beams in compression and bending around the strong axis, part 1 – derivations Slender timber beams in bending can be designed using different methods in view of out‐of‐plane stability. Lateral torsional buckling may be verified either using the so called equivalent member method or by means of 2nd order calculations, considering equivalent imperfections. However, at present determining the lateral torsional buckling resistance using either of these both methods, leads to different results. In this paper, the background of both verifications is investigated in deep. Moreover, as an alternative approach, a non‐linear calculation with an imperfection shape in affinity to the critical shape is presented in part 1 of this paper. If the curvature amplitude is scaled, the same results as by the equivalent member method are achieved. It is shown that plasticity effects can be considered with high precision as well. In part 2, results of experimental tests on lateral torsional buckling of glued laminated timber and laminated veneer lumber beams are presented, with nearly ideal boundary conditions and load remaining vertical through‐out the test. Based on these test first tentative values can be obtained for the imperfection compatible with the alternative lateral torsional buckling approach presented. [ABSTRACT FROM AUTHOR]

Consideration of an eccentric load introduction in the buckling check acc. to the reduced stress method in EN 1993‐1‐5:2019 – part 1: experimental studies During incremental launching, the cross‐section of a bridge is stressed by biaxial stresses due to the load introduction from the launching bearing on the last pier and the bending moment occurring there. In addition, unavoidable eccentricities from the load introduction occur, which could result in an additional out‐of‐plane bending at the web. While manufacturing‐related tolerances in form of imperfection coefficients or geometric equivalent imperfections are already taken into account in the current regulations for the buckling verification acc. to DIN EN 1993‐1‐5:2019, they do not include eccentricities of the load introduction from the launching bearings. In practice, therefore additional verifications are often required which are not regulated by standards and consequently cause significant additional work for the design and execution. In order to solve this problem, large‐scale buckling tests and numerical calculations were carried out as part of the buckling investigation for the Thulba viaduct and the research project on the buckling verification of longitudinally stiffened plates under multiaxial loading. Based on these, a proposal for the consideration of an eccentric load introduction in the buckling verification was developed by the main author. The present part 1 of this publication describes the experimental and numerical investigations on the effect of an eccentric load introduction considering different types of launching bearings. The results are then compared with the current regulations of the standard in a part 2. Furthermore, in part 2 a proposal for the consideration of an eccentric load introduction by implementing an eccentricity coefficient in the buckling verification using the method of reduced stresses is presented. [ABSTRACT FROM AUTHOR]

Translation abstract Investigations on bonded stiffeners in steel and composite bridgesNumerous bridges are in poor condition. In particular, resistance to plate buckling is a problem. Strengthening of buckling‐prone sections in steel bridges is often difficult due to non‐weldable steels and the additional notch effect from conventional joining techniques. The use of adhesives for fixing stiffeners allows material‐friendly reinforcement of buckling‐prone steel sections. Prior to practical application, numerous questions must be answered with regard to the detailing of the stiffeners, the stress on the adhesive layer due to inhibiting buckling, the load‐bearing capacity of the adhesive layer, the resistance to aging and fatigue. On the basis of numerical and experimental investigations, a simple fracture condition could be developed which allows a design of the adhesive layer‘s load‐bearing capacity. A sufficient stiffening effect of the bonded stiffener is given as long as the adhesive layer‘s load‐bearing capacity is sufficient. The aging and fatigue behaviour was investigated in basic tests. It was possible to define boundary conditions that enable resistance for a limited time, but there is still need for further research in this field. [ABSTRACT FROM AUTHOR]

Universal high‐performance columns made of high‐strength steels without welding In recent years, steel‐concrete composite columns made of normal‐strength steels are seldom used owing to the economic and technological advantages of precast reinforced concrete columns. Though, the use of high‐strength structural steels bears high potential for the efficient production of composite columns with excellent structural performance that are economically competitive to precast concrete columns, there are currently major obstacles to use of the ultra‐high‐strength steels (UHSS) in Germany. Hollow section composite columns with embedded high strength steel core without welded connections provide an opportunity to regain lost market share. A research project, funded by the AiF (Arbeitsgemeinschaft industrieller Forschungsvereinigungen), is intended to explore the potential of UHSS composite columns by experimental and theoretical investigations. The present paper demonstrates the concept of such composite columns with UHSS and gives first exciting insights into the research results. In addition to column tests under ambient and fire conditions, small scale tests are necessary to investigate various influencing factors and to create the basis for new and easy to use design and construction principles that allow efficient application. [ABSTRACT FROM AUTHOR]

Experimental investigations on novel composite columns with a concrete filled hollow section and high‐strength steel plates as core in ambient and fire conditions High‐performance composite columns are commonly carried out with solid steel sections as core profiles. These profiles imply limitations due to reductions of the yield strength depending on the thickness and high residual stresses. In this publication, the authors present a novel section consisting of a concrete filled circular hollow section with locally connected steel plates as core. To increase the load bearing capacity, steels with yields strengths up to 960 N/mm2 are used. Experimental investigations for ambient conditions and in case of fire are presented. The columns showed a promising load bearing behaviour. These investigations will serve as basis for a systematic development of this innovative, high‐performance composite column with a corresponding design concept. [ABSTRACT FROM AUTHOR]

Abstract: Failure of a steel pallet rack in Athens. Pallet racking systems have peculiar characteristics which differ from usual steel structures that make them sensitive to stability failure modes. In the present paper a rack failure is presented where the rack has failed due to lateral torsional and distortional buckling of its most stressed uprights. The structural behavior was studied by a combination of experimental and numerical/analytical methods. The investigations included test loading, bending tests on pallet beams, compression tests on stub column and bending tests on beam end connectors. Subsequently, a global geometrical non‐linear analysis is performed on the 3‐D system. Its results indicate by comparison with the pictures of the actual structure that the collapse mode is correctly detected. Conclusions are drawn that recommend the performance of static and dynamic analyses on an obligatory basis. [ABSTRACT FROM AUTHOR]

Steel tube struts in braced excavations – Simplified design for cross section class 4 Steel tubes are often used as excavation struts. When designing long struts without intermediate supports, tubes with large diameter and small wall thickness are particularly economical. This may lead to reaching the limit of cross section class 4 requiring a shell buckling analysis according to EN 1993‐1‐6. In this article a simplified design method using section‐related buckling stresses based on EN 1993‐1‐6 Annex D is described. Ready‐to‐use section‐related buckling stresses are given for commonly used steel tubes of cross section class 4. [ABSTRACT FROM AUTHOR]

Allowable compressive rail force due to track‐bridge‐interaction for ballastless track On modern continuously welded railway tracks on bridges the rails are exposed to additional axial stresses due the interactions between the track and the bridge. On ballasted track the total compressive force within the rail must be limited to prevent rail buckling. In the 1980s extensive theoretical and experimental research was conducted and a limit value for the additional compressive rail stress of 72 MPa was introduced. For the more ridged ballastless track systems this limit value was raised to 92 MPa. However, this was done without any transparent scientific basis. For the case of the Itz Valley Bridge on the new highspeed line between Ebensfeld and Erfurt the calculated additional stresses due to the track‐bridge‐interaction could not be verified with these limit values. To determine a new case specific limit value for the additional compressive rail stresses extensive investigations were conducted and are presented within this article. The behaviour of the ballastless track system under high compressive rail forces was analysed numerically and experimentally. As a result, failure mechanisms and limit states were defined and verified for secure combinations of input parameters. This example shows the potential of the system to withstand high compressive rail forces and presents a possible method to define new limit values for the additional compressive rail stresses for ballastless track systems on bridges. [ABSTRACT FROM AUTHOR]

Translation abstract Current steel construction research for offshore wind energyThis report begins with an overview of current and future developments in offshore wind energy. The focus is on steel support structures. The so‐called monopiles dominate here. Jacket constructions made of tubular sections are used to a much lesser extent. Due to the high dynamic demands and the simultaneously adverse environmental conditions at sea, steel construction‐specific questions arise for research. The Institute of Steel Construction of Leibniz University Hannover has been focussing on these topics for 25 years now. This article addresses three topics typical of steel construction: Connection technology, stability and fatigue. First, it deals with yield point‐controlled tightening of prestressed bolted joints with high‐strength bolts. Then the non‐linear numerical determination the load bearing capacity of shell structures under axial and circumferential pressure, as required for the design of so‐called suction buckets, will be reported on. Finally, research is presented considering the quantification of corrosion on fatigue strength. [ABSTRACT FROM AUTHOR]

Abstract: Calculation of corrugated wall sheet silos. Corrugated wall sheet silos are one of the most constructions of storing agricultural products. Until the introduction of the DIN EN regulations in 2010 the calculation and the design performance of these corrugated wall sheet silos were carried out essentially according to DIN 18914: 1985‐09. This standard has been canceled without replacement and has been replaced by DIN EN 1993‐4‐1 and other regulations according to DIN EN. The complexity of the ”new“ norms is well known. It is reported on the experience how the simple design and calculation concept of the silo container can be implemented relatively simply within the very extensive DIN EN regulations. [ABSTRACT FROM AUTHOR]

Transversal load introduction into unstiffened girder webs – interaction with shear force and bending moment and implementation in new Eurocode version Transversal load introductions into unstiffened girder webs are often used economic solutions in building structures, not directly covered in the current Eurocode. Within this paper an engineering design model, developed at TU Graz, is evaluated for cases with additional high shear forces and bending moments acting at the girder. The resulting load carrying behaviour, in cases of interaction between Fz & Vz & My, is presented, based on comprehensive numerical studies, also for girders which are susceptible to web buckling. Finally, the modified design model is presented, which will be part of the new Eurocode version prEN 1993‐1‐1. In addition, a more general solution is shown, which could also be implemented in the Eurocode in form of a national Annex. [ABSTRACT FROM AUTHOR]

Abstract: Introduction of the Direct Strength Method into the design of cold formed steel members according to EN 1993‐1‐3. Cold formed steel members have a varied area of applications in steel lightweight constructions but are subject to local and global instabilities due to compressive and bending stress. The design method of the European Standard EN 1993‐1‐3 is based on the Method of Effective Widths covering local and distortional buckling. Unfortunately, an EN 1993‐1‐3 design is time‐consuming and prone to errors, furthermore the results are often conservative. This paper is going to introduce a new, practical design method for cold‐formed steel sections that combines the established European regulations of global instabilities with the Direct Strength Method (DSM) described in the North American standard AISI Standard 100 regarding local stability analysis. Based on comparative studies of mono‐symmetric cross‐sections it is possible to demonstrate that this new method offers a great potential of improving the design of cold‐formed sections, additionally improves the economic efficiency of lightweight steel sections. More theoretical and experimental investigations are needed, deeper leading questions are to answer, until this method is able to supplement the European standard. [ABSTRACT FROM AUTHOR]

Bar bundle columns with high‐strength reinforcing steel As part of the AiF project "Bar bundle columns with high‐strength reinforcement steel" the load‐bearing behavior of bar bundle columns in cold and fire conditions was investigated. Bar bundle columns are a new type of composite columns. To this purpose, a bundle of high‐strength reinforcing bars with a yield strength of 670 MPa is placed in a steel tube and then grouted with mortar. The bundle can consist of 1, 3, 7 or 19 bars. To analyze the load‐bearing behavior, relevant material parameters were determined in cold and in fire conditions. Subsequently, large‐scale buckling tests were carried out under room temperature and in fire case. Considering the obtained results, an FE model was created and calibrated. On this basis, a design concept was developed. [ABSTRACT FROM AUTHOR]

Four new mixed-valent chain alkali metal (A) sulfido ferrates of the general structure family A 1 + x Fe x II Fe 1 − x III S 2 ${A}_{1+x}\left[{\text{Fe}}_{x}^{\text{II}}{\text{Fe}}_{1-x}^{\text{III}}{\text{S}}_{2}\right]$ were synthesized in the form of tiny green-metallic needles from nearly stoichiometric melts reacting elemental potassium with natural pyrite (A = K) or previously prepared Rb2S/Cs2S2 with elemental iron and sulfur (A = Rb/Cs). The crystal structures of the compounds were determined by means of single crystal X-ray diffraction: In the (3+1)D modulated structure of K7.15[FeS2]4 (space group Ccce(00σ3)0s0, a = 1363.87(5), b = 2487.23(13), c = 583.47(3) pm, q = 0,0,0.444, R1 = 0.055/0.148, x = 0.787), a position modulation of the two crystallographically different undulated [ FeS 4 / 2 ] ∞ 1 ${}_{\infty }{}^{1}\left[{\text{FeS}}_{4/2}\right]$ tetrahedra chains and the surrounding K cations is associated with an occupation modulation of one of the three potassium sites. In the case of the new monoclinic rubidium ferrate Rb4[FeS2]3 (x = 1 3 $\frac{1}{3}$ ; space group P21/c, a = 1640.49(12), b = 1191.94(9), c = 743.33(6) pm, β = 94.759(4)°, Z = 4, R1 = 0.1184) the undulation of the tetrahedra chain is commensurate, the repetition unit consists of six tetrahedra. In the second new Rb ferrate, Rb7[FeS2]5 (x = 0.4; monoclinic, space group C2/c, K7[FeS2]5-type; a = 2833.9(2), b = 1197.36(9), c = 744.63(6) pm, β = 103.233(4)°, Z = 4, R1 = 0.1474) and its isotypic mixed Rb/Cs-analog Rb3.6Cs3.4[FeS2]5 (a = 2843.57(5), b = 1226.47(2), c = 759.890(10) pm, β = 103.7170(9)°, R1 = 0.0376) the chain buckling leads to a further increased repetition unit of 10 tetrahedra. For all mixed-valent ferrates, the Fe–S bond lengths continuously increase with the amount (x) of Fe(II). The buckling of the chains is controlled through the local coordination of the S atoms by the variable number of A cations of different sizes. [ABSTRACT FROM AUTHOR]

Abstract: Equivalent initial imperfections for applying the partial internal forces method for flexural buckling about the weak axis. This paper compares design approaches for equivalent initial imperfections of steel members with hot‐rolled double symmetric I‐/H‐profiles subjected to buckling about the weak axis. In addition to the normative rules applied in Germany and Europe, design approaches for imperfections are also taken into account, which are currently discussed as part of the further development of Eurocode 3. A proposal using the partial internal forces method allows a consistent design for steel members taking into account the cross‐sectional failure as well as the flexural buckling about the strong and weak axis. The proposal leads to design results that agree well with the results of numerical simulations. [ABSTRACT FROM AUTHOR]

Shell structures made of stainless steels are used e. g. in tank structures and biogas plants. They are fully recyclable, do not need any corrosion protection and therefore, they are valuable in terms of environmental protection and environmental compatibility. However, the design of these shells with regard to their buckling resistance is limited according to DIN EN 1993-1-6 due to the non-linear stress-strain-behaviour of stainless steels. For this reason, additional temperature and slenderness dependent buckling strength reduction factors for axial loaded cylindrical shells made of austenitic stainless steels were already developed by Schmidt and Hautala. The transferability of these buckling strength reduction factors on shell structures made of ferritic and duplex stainless steels will be reviewed in the context of the European RFCS research project BiogaSS by means of experimental, numerical and theoretical studies. The results shall be incorporated in the revision of DIN EN 1993-1-6. [ABSTRACT FROM AUTHOR]

Abstract: Presently, numerical analysis of the finite element method and small‐scale tests are commonly adopted in researches on the shear behaviour of girders with corrugated steel webs, but these two methods are unable to deal well with the effects of construction flaws in actual structures. Besides, in the case of girders with trapezoidal corrugated webs, most studies took steel I‐shaped specimens with vertical webs and thin flanges as research objects, and these cannot represent girders with inclined webs or composite flanges. Therefore, a full‐scale corrugated steel web girder with inclined flanges was tested. The failure mode and shear strength of the girder were investigated. The results show that the shear resistance of flanges should not be ignored. Out‐of‐plane deformation develops in the web from the start of loading owing to initial geometric imperfections, and buckling failure occurs in areas where out‐of‐plane deformation develops fastest. [ABSTRACT FROM AUTHOR]

Abstract: Optimal use of hollow sections in bridge construction. Structural steel hollow sections can be used to design aesthetic, efficient and elegant bridges as truss structures. Their excellent load‐bearing capacity with low risk of buckling and high torsional resistance makes hollow sections the perfect choice for compression members and in truss constructions. Bridges using hollow sections have a better load‐to‐weight ratio compared to other forms of designs, reducing material consumption. Large spans are no problem with hollow sections. Ultimately this allows for light, airy structures that blend aesthetically into our environment. The surface, and thus the coating area, is comparatively small and there are no sharp edges that can cause problems with corrosion or dirt can deposit. According to ZTV‐ING [14], only hot finished hollow sections in accordance with EN 10210 [5] may be used as materials for structural components. In order to maintain a technically safe, economical and architecturally attractive structure, the planner should think about the connections as well as the construction and erection at an early stage of design. The high degree of prefabrication in steel construction should be used where possible to shorten the construction time and minimize the disruption of traffic. Maintenance and durability should also be considered with regard to the accessibility of the structure. [ABSTRACT FROM AUTHOR]

Abstract: The use of High Strength Steel (HSS) S690 in highway bridge decks is not yet widespread. A research program investigated the optimal use of HSS in bridges. A comparative design was performed for a 21.5 m wide highway bridge, with a typical 80 m long inner span and a steel‐concrete composite twin plate girder deck, using the Eurocode standards. Three designs were produced: Design (A) with S355 NL steel grade, Design (B) with HSS S690 QL/QL1, and Design (C), also with HSS S690, but exploring different design options provided by welded joint treatments to improve fatigue and suggest possible enhancement of the present Eurocode rules. General guidelines for the design of highway bridge decks using HSS S690 are provided. [ABSTRACT FROM AUTHOR]