Search

Investigations on material requirements of high‐strength steels – FOSTA research network HOCHFEST Structural steels with higher strengths enable slender and material saving, thus particularly sustainable construction. In the second generation of EC3‐1‐1, which will be applied in the future, design of steel structures is already possible up to steel grade S700. However, already now, the standardization committee CEN/TC/250/SC3 has commissioned the respective WG12 to prepare rule proposals for the Eurocodes for the design of steel structures using steel grades in the range S700 to S960. Clarification of the material requirements in this context is at the very beginning of the works. The question arises as to whether the set of requirements as formulated so far for the steels up to S700 can continue to exist not only in the amount of minimum or limit‐values, but also whether the type of requirements would then still be appropriate. This article reports on the status of the investigations in this respect of a research project P1509 set up within the framework of High Strength Research Network (HOCHFEST). It discusses the current material requirements with regard to a transfer to steels up to S960 in type and value, gives an overview of the research methods and points out possible alternatives. The research project is not yet completed and further results are therefore to be expected. However, tendencies are already emerging. [ABSTRACT FROM AUTHOR]

Design method for bonding ultra‐high‐strength steel materials in agricultural machinery construction In agricultural machinery constructions made of thick metal sheets (approx. 3–10 mm), adhesive bonding technology has so far only been used to a limited extent, even though it is already an established joining method in other areas of application and offers many advantages over other joining methods because up to now there has been a lack of regulations for the design of such joints. An essential criterion in designing joints in agricultural machinery construction is fatigue strength because the long service life of the products is decisive. Bonded joints exhibit excellent behaviour under cyclic loading. The increasing demands for resource efficiency and lightweight construction are leading to a rethink in agricultural machinery and plant construction because this can be implemented by using higher‐strength steel materials in combination with adhesive bonding technology. The aim is to develop a methodology for designing bonded joints in constructions with high‐strength steel materials based on the FKM guideline. The operationally relevant loads of agricultural engineering are analysed and examined on technological and component‐like test specimens. The mechanical, thermal, and medial influencing factors and the influence of the bonded joint geometry and the operating load collectives are investigated. The findings are summarised in an SME‐relevant procedure for determining reduction factors, making it possible to calculate the component strength statically and dynamically. [ABSTRACT FROM AUTHOR]

High‐rise building columns in Germany – Potential analysis under consideration of sustainability Modern and economical constructions of high‐rise buildings require columns with high load‐bearing capacity, which also meet architectural, technical and economic requirements in addition to the safe design. From a review and classification of column concepts on high‐rise buildings in Germany in concrete construction over the last 30 years, an optimization sequence from "concrete" to "reinforcement" to "production" can be determined. The effects of the optimization strategies are presented in a qualitative potential analysis under the aspects "load‐bearing capacity, robustness, construction time, costs and sustainability" and show a clear trend towards precast columns with high‐strength concrete, high‐strength reinforcement and high reinforcement degrees (3H‐columns). From further increasing requirements for sustainability, but also for closing deficits in the standards in case of modern high‐rise columns, current research issues arise. In this relation, research approaches and proposed solutions are presented. [ABSTRACT FROM AUTHOR]

Emissivity of zinc‐aluminum coatings under fire loading and effect on the fire resistance In the recent past, a reduced emissivity under fire load has been proofen for classic hot‐dip galvanized steel, which proves to be advantageous compared to an unprotected steel member in the fire design according to DIN EN 1993‐1‐2. In the course of further investigations, the emissivity of modern zinc‐aluminum coatings, which are characterized by a coating characteristic that differs from the standard coatings depending on the aluminum content, was determined on the basis of small scale samples, with various configurations being tested. The results for all variants show that ZnAl coatings exhibit a further improvement in emissivity compared with pure zinc or quasi‐pure zinc coatings, and in particular a reduction in emissivity at higher temperatures. The application of these coatings has a positive effect on the fire resistance of steel components galvanized with ZnAl alloys in the form of a slower heating and thus a higher load‐bearing capacity under fire load determined in the course of the fire design, and the potential for reducing the steel profile cross‐section and thus saving resources by a relevant order of magnitude. [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]

HFMI‐treatment of ultrahigh‐strength steels – extension of the DASt‐guideline 026 In the case of highly loaded steel structures such as wind towers or bridges, the use of newer ultra‐high‐strength structural steels is interesting, but the fatigue verification is usually decisive for these structures. Standards and guidelines specify detail categories for fatigue assessment that are independent of material strength, so there is no benefit regarding the use of high‐strength steels in fatigue loaded structures. By using post‐weld treatment by high‐frequency mechanical impact treatment (HFMI), the fatigue strength of welded joints can be increased to a great extent. Previous investigations show an increasing effectiveness of HFMI‐treatment with increasing material strength. The new DASt‐guideline 026 gives rules for the fatigue assessment of constructional details made of steel grades reaching from S235 to S700 after the application of HFMI‐treatment. An extension for steels up to a steel grade of S960 is pending and geometric imperfections exceeding weld quality level B of ISO 5817 are not covered yet. The objective of the current AiF‐FOSTA project 21410 BG (P 1505) is to develop the basis for an extension of the DASt‐guideline 026 for high strength steels up to a steel grade of S960 and to investigate the influence of increased imperfections on the fatigue strength of HFMI‐treated welds. Therefore, experimental investigations are carried out on constructional details with and without imperfections. Moreover, the influence of various imperfections is analysed numerically. In the following, the project is presented and first project results are shown. [ABSTRACT FROM AUTHOR]

Effective design concepts for welded mixed connections in steel structures Mixed connections made of normal strength and high strength steels enable optimal material use to the forces acting on them. This leads to ecological and economic advantages through reduced material consumption and smaller weld geometries. Normative rules for butt‐welded mixed connections of normal strength and high strength steels do not exist, therefore a design approach for such connections is to be developed in the research project "Effective design concepts for mixed connections in steel structures". In addition, the design concepts already developed for butt‐welds and fillet‐welds are being extended up to S960, in order to integrate the results into the new version of EN 1993‐1‐12. For this purpose, extensive experimental investigations of the load‐carrying capacity are carried out by varying the base material, welding consumable, heat input, plate thickness and weld geometry. With the results obtained and further accompanying investigations, the influences of the varying parameters on the load‐carrying capacity of the welded connections will be identified. First results of that project are reported in the following. [ABSTRACT FROM AUTHOR]

The article provides information on the advancement of weldable stainless steel, high strength and corrosion resistance and welding technology processing. Topics include different types of stainless steel such as austenitic and ferritic, effect of chromium and stress corrosion cracking increasing the strength of the material.

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]