Numerical evaluation of the plastic hinges developed in headed stud shear connectors in composite beams with profiled steel sheeting

[EN] For composite beams using novel steel sheeting, the current Eurocode 4 rules sometimes overestimate the load bearing capacity of the shear connector. This is due to the larger rib heights and the smaller rib widths in comparison with the old studies, which have been carried out to calibrate the current design equations. The RFCS Project “DISCCO” investigated this phenomena and the working group under mandate M515, CEN/TC250/SC4/SC4.T3 is enhancing this equation and working on a proposal to be taken over in the new version of Eurocode 4.The proposed new equation covers the failure behaviour of the shear connection more in detail. The test results show, that the failure consists in a combined concrete cone and stud in bending. Due to the geometry of novel steel sheeting, the load bearing capacity of the headed stud shear connector is no more limited by its shear capacity, but by its bending capacity.A 3D non-linear finite element model is developed and validated through the support of the DISCCO push-out tests. A good agreement between numerical and experimental results in terms of force-slip behaviour is achieved. Special attention of this work lies on the numerical evaluation of the number of plastic hinges ny: a stress-based procedure is presented and the results are compared to the equations presented for new Eurocode 4.The numerical simulations show that the upper plastic hinge moves up as the slip increases due to the progressive crushing of the concrete in the rib. From the parametric study, it turns out that ny is linearly proportional to the embedment depth. Compared to pre-punched hole decking, through-deck welding specimen activates less plastic hinges in the studs because of the higher stiffness provided at the base of the stud.The RFCS project “DISCCO” was supported by the grant agreement number RFSR-CT-2012-00030. Further, the authors gratefully acknowledge the support of ArcelorMittal Global R&D, Long Products Luxembourg.Vigneri, V.; Odenbreit, C.; Braun, M. (2018). Numerical evaluation of the plastic hinges developed in headed stud shear connectors in composite beams with profiled steel sheeting. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 229-236. https://doi.org/10.4995/ASCCS2018.2018.7166OCS22923

Development of an innovative type of shear connector dedicated to fully embedded steel-concrete composite columns – experimental and numerical investigations

[EN] A shear connection in steel-concrete composite columns is established in the normal case with headed shear studs. However, this type of connector was developed for composite beams and in terms of composite columns, a wide range for an optimisation still can be identified due to the different geometries of steel profiles, concrete and reinforcement. The presented paper shows investigations on a new type of shear connector with a direct application to composite columns and with a potential for a fully automatic fabrication process. The proposed new type of shear connection is made out of reinforcement bars welded to the external surfaces of the steel profile’s flanges. The experimental campaign consisted of 12 composite push-out tests with a column section geometry. The analysed specimens included centrally embedded HEB120 steel profiles into 340x1000x450mm concrete blocks. All the tests have been categorized into 4 groups. One group per connector was defined (including group without mechanical connector). Each group had 3 identical specimens. Surface treatment conditions, reinforcement arrangement, used materials and test layout were the same in all executed tests. The acquired results showed a good performance of the proposed solutions and allowed to identify the different load-bearing behaviour. After the test execution, the specimens were opened and the failure pattern have been investigated. The testing campaign was supported by numerical simulations performed with the finite element software code Abaqus®. In the developed models, a new approach to simulate the steel-concrete bond was implemented.The MultiCoSteel research project is running in a collaboration with the industrial partner ArcelorMittal. It is funded by the National Research Fund, Luxembourg, FNR AFR-PPP PhD Grant (Call 2016-1), Proj. Ref. 11283614. Numerical experiments presented in this paper were carried out using the HPC facilities of the University of Luxembourg – http://hpc.uni.lu.Chrzanowski, M.; Odenbreit, C.; Obiala, R.; Bogdan, T.; Braun, M.; Degee, H. (2018). Development of an innovative type of shear connector dedicated to fully embedded steel-concrete composite columns – experimental and numerical investigations. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 427-434. https://doi.org/10.4995/ASCCS2018.2018.6970OCS42743

Analyses of the loadbearing behaviour of deep-embedded concrete dowels, CoSFB

The development of the “CoSFB-Betondübel” is presented in this paper. The “CoSFB-Betondübel” is a deep-embedded concrete dowel connecting in situ concrete with a steel section to assure composite action and thus allow for composite beam design. The loadbearing behaviour and parameters influencing this behaviour were determined through experimental tests. Special focus was given to the influence of the ratio of the resistance of the concrete dowel to the concrete compression class. The evaluation of the results concluded in a National Technical Approval [1]. Further investigations were performed via FE analysis in ABAQUS. Further, 3D models with non-linear material and geometry were prepared and validation undertaken. In addition, a real application example of CoSFB is shown

Dynamic thermal simulations for developing early-stage assessments for office buildings

Office buildings account for a large portion of the total energy consumption in Europe because due to increased comfort requirements almost all recent buildings are air-conditioned. This project is focused on the influence of thermal storage capacity of commonly used structure types of office buildings and different technical strategies on energy efficiency and thermal comfort. The technical parameter ventilation strategy is essential compared to the parameters structure type or window-to-wall ratio. Additionally a lighting control system based on solar radiation shows a high influence on the internal gains and in consequence on the overheating hours. The slab type respectively the accessibiltiy of the thermal mass has a significantly higher influence than the differences of “massivity” between solid and light weight structures

Failure behaviour of silicone adhesive in bonded connections with simple geometry

In façade structures, adhesively bonded connections between glass panels and metallic substructures represent an attractive alternative to mechanical fixation devices. Apart from positive aspects regarding the construction's energy efficiency and aesthetics, the uniform load transfer reduces stress concentrations in the adherends, which is beneficial especially regarding brittle materials like glass. Structural silicone sealants are generally used for these kind of applications due to their excellent adhesion on glass and their exceptional resistance against environmental influences and ageing. For the verification of the bonded connection, non-linear numerical simulations, such as the Finite Element Method, are increasingly used. The resulting three-dimensional stress states need to be assessed with the help of an appropriate failure criterion. In this paper, an overview is given on available failure criteria for rubber-like materials. The applicability of these criteria on the silicone sealant is verified regarding three characteristic stress states: uniaxial tension, shear and compression. The proposed engineering failure criterion is the true strain magnitude, which is valid for bonded connections in form of linear beads for cohesive failure of the adhesive. For Dow Corning® 993 structural silicone sealant, the strain magnitude, evaluated using true strains, at failure could be determined as 1.6

Identification and Characterization of Helicobacter pylori Genes Essential for Gastric Colonization

Helicobacter pylori causes one of the most common, chronic bacterial infections and is a primary cause of severe gastric disorders. To unravel the bacterial factors necessary for the process of gastric colonization and pathogenesis, signature tagged mutagenesis (STM) was adapted to H. pylori. The Mongolian gerbil (Meriones unguiculatus) was used as model system to screen a set of 960 STM mutants. This resulted in 47 H. pylori genes, assigned to 9 different functional categories, representing a set of biological functions absolutely essential for gastric colonization, as verified and quantified for many mutants by competition experiments. Identification of previously known colonization factors, such as the urease and motility functions validated this method, but also novel and several hypothetical genes were found. Interestingly, a secreted collagenase, encoded by hp0169, could be identified and functionally verified as a new essential virulence factor for H. pylori stomach colonization. Furthermore, comB4, encoding a putative ATPase being part of a DNA transformation-associated type IV transport system of H. pylori was found to be absolutely essential for colonization, but natural transformation competence was apparently not the essential function. Thus, this first systematic STM application identified a set of previously unknown H. pylori colonization factors and may help to potentiate the development of novel therapies against gastric Helicobacter infections

Investigations about the load bearing- and strain behavior of the concrete slab in the range of composite connections

Due to the rising cost pressures in the construction industry, it is particularly important to choose efficient design methods to achieve economic structures. The use of the plastic hinge theory may lead to good results within the steel and composite construction industry because cross section- and system reserves can almost fully used. This means for the normal composite beam a redistribution of the bending moment from the support section to the field section. This redistribution causes an increase of the rotation at the composite connection. The presented tests show the influence of the reinforcement (type of reinforcement and reinforcement ratio) to the rotation capacity of the connection. The increased rotation requirements of composite connections in the area of plastic hinges should already be take in to account at planning state.Aufgrund des steigenden Kostendrucks im Bauwesen ist es besonders wichtig, bereits bei der Planung effiziente Berechnungsmethoden heranzuziehen, die zu einer wirtschaftlichen Bauweise führen. In der Stahl- und Verbundbauweise kann dabei die Anwendung der Fließgelenktheorie zu guten Ergebnissen führen, da sowohl Querschnitts- als auch Systemreserven nahezu vollständig ausgenutzt werden. Beim gewöhnlichen Verbunddurchlaufträger führt dies zu einer Umlagerung des Stützmomentes hin zum Feld. Diese Umlagerung bedingt eine Zunahme der Rotation im Anschluss. Die hier vorgestellten Versuche zeigen, wie die Art und Menge der Bewehrung Einfluss auf die Rotationskapazität des Verbundanschlusses ausübt. Den erhöhten Rotationsanforderun gen von Verbundanschlüssen im Bereiche von Fließgelenken sollte bereits bei der konstruktiven Ausbildung der Anschlüsse Rechnung getragen werden

Development new push test Eurocode 4

The standard push test specimen in the current version of Eurocode 4 does not provide any information on what modifications should be made when profiled steel sheeting is introduced. Whilst the lack of information was intended to encourage innovation, this has sometimes lead to test results implying that stud connectors possess a lower resistance and ductility than assumed in current Standards. From full-scale beam and companion push tests in Europe, it has been shown that modifying the push test through the introduction of a normal force to the face of the test slabs provides comparable load-slip performance to that encountered within a beam. Within the work programme for developing the second generation of Eurocodes, this paper presents part of the background to Sub-task 1 of SC4.T3, whose aim is to develop an improved push test for Eurocode 4 when stud connectors are welded within profiled steel sheeting

A Reusable Structural System Fit for Geometrical Standardisation and Serial Production

A series of demountable connections for reusable composite flooring systems and a standardized adjustable steel connection have been developed and tested, to facilitate circular economy as well as the serial production of structural elements and the suitability to be added into BIM or other digital tools. Demountable beam and floor elements and adjustable steel con-nections form the basis of a Lego-liked ‘plug and play’ circular framed structural system. This paper presents the proposed circular system, the results from experiments and finite element analyses and indicates the analysing methods for structural engineers to open a path way for fully implementation of the structures ‘as built’ into digital tools, fabrication and construction