Discussion of an algorithm to transfer arbitrary shear connector load-slip curves into an effective shear resistance

in Kolloquiumsband - 23 DASt-Forschungskolloquium (2022, February 22)

The RFCS research project REDUCE (Project No. 710040) investigated dismountable shear connections with preloaded bolts. These connectors have in most cases a slip capacity greater than 6 mm and show a ... [more ▼]

The RFCS research project REDUCE (Project No. 710040) investigated dismountable shear connections with preloaded bolts. These connectors have in most cases a slip capacity greater than 6 mm and show a monotonic increasing nonlinear load-slip behaviour without plastic plateau and failure of the bolt in shear. Current design procedures of steel-concrete composite beams are largely based on the implementation of headed shear studs, which exhibit a rather different load-slip behaviour with a pronounced plastic niveau. Thus, a question turned out, which compression force can be activated by the shear connection in the concrete girder of a composite beam and how can the respective ultimate bending capacity be determined. Hence, this contribution presents an analytical algorithm to estimate the occurring compression force in the concrete girder when demountable shear connectors are used. The proposed algorithm bases on the actual measured load-slip curve of the shear connection and the expected slip along the beam, which is estimated for each single connector to later determine the compression force in the concrete girder. In addition to the explanation of the “general algorithm”, assumptions for practical use have been made for the slip distribution to simplify the calculation of the compression force and an effective shear resistance P_Rd,eff. [less ▲]

A Reusable Structural System Fit for Geometrical Standardisation and Serial Production

in Proceedings of the XIII Steel and Composite Construction Conference (2021, November 25)

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 ... [more ▼]

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 connections 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. [less ▲]

Demountable and reusable construction system for steel-concrete composite structures

in Odenbreit, Christoph; Kozma, Andras (Eds.) Demountable and reusable construction system for steel-concrete composite structures (2020, October 30)

In the face of climate change and the depletion of finite resources, sustainability is becoming increasingly important recently. This is especially true in the construction industry that is responsible ... [more ▼]

In the face of climate change and the depletion of finite resources, sustainability is becoming increasingly important recently. This is especially true in the construction industry that is responsible for the 11% of global carbon dioxide emissions. Besides the technological improvements, the emissions can be further reduced by the application of the principles of the circular economy. This concept is based on the efficient allocation of resources. Three terms are frequently used when talking about this concept: reduce, reuse and recycle. Reducing is cut-ting back on the amount of waste we produce, reusing is finding a new way to use our products so that they do not be-come waste, and recycling is using the materials of our products to produce new materials. The traditional life-cycle of a building usually follows a linear model from the extraction of the raw materials through material production, component manufacturing, construction and building use, until when finally the building is demolished and most of the materials become debris and go into landfill. This is in direct opposition with the concept of circular economy. With proper considerations at the design stage, it is possible to deconstruct whole buildings and re-erect them elsewhere. In the frame of the RFCS Research Project “REDUCE” of the European Commission, a demountable and reusable construction system for steel-concrete composite structures has been recently developed. The system is based on a modular “kit-of-parts” system that uses prefabricated and standardised elements that are easy to manufacture and to assemble with the help of standardised connections. The elements were designed in a systematic way such that, a wide variety of different configurations are possible. In this system, the geometry of all elements respects the planning grid that is based on a basic module size. The research included the development and structural testing of novel demountable and adjustable structural solutions including beam-to-slab, beam-to-beam and beam-to-column connections. During the development of the structural solutions the following aspects were considered: structural performance, safety, installation and tolerances, demountability, corrosion resistance, aesthetics, economy, adaptability, standardisation and environmental impact. The laboratory testing was supplemented by nonlinear numerical studies using the finite element software ABAQUS. Based on the results and the experiences obtained throughout the research project, a design proposal was prepared. One objective of the project was to find structural solutions that are easily applicable and compatible with the current standard de-sign rules. The proposed beam-to-beam and beam-to-column joint is in the scope of EN1993-1-8. The new shear connections behave differently than the traditionally applied welded studs. The cor-responding standard would not allow the equidistant placement of the connectors nor the application of the partial shear theory. This would make the use of demountable shear connections complicated and uneconomical. In order to overcome this issue, a simple algorithm was developed that transforms the elastic-brittle shear connection behaviour into an equivalent ductile rigid-plastic behaviour so that the Eurocode 4 design rules for the determination of the moment resistance of composite beams with partial shear connection remain applicable. The design proposal also contains recommendations to maximize the reuse potential of the building components. This paper presents a general overview of the developed construction system and the corresponding laboratory tests and numerical studies as well as recommendations for the design and application of de-mountable and reusable composite structures. [less ▲]

Parametric study on non-ductile demountable shear connectors

in ce/papers (2019, September), 3(3-4), 283-288

The basic principle of the circular economy is to reduce or totally eliminate waste and carbon dioxide production with the help of a multiple, efficient usage of resources. The application of reusable ... [more ▼]

The basic principle of the circular economy is to reduce or totally eliminate waste and carbon dioxide production with the help of a multiple, efficient usage of resources. The application of reusable structural elements plays an important role and can contribute essentially to a low-carbon future. Within the European research project REDUCE (Grant Agreement number: 710040), composite beams and steel-based flooring systems, which are demountable and reusable, have been developed and investigated. The experimental investigations showed that the structural behaviour of the newly developed shear connectors differs from the behaviour of the traditionally applied welded studs. Some behave in a non-ductile way. In order to assess, how far the regulations of EN1994-1-1 for shear connections can still be applied, parametric studies have been conducted. The respective numerical models were developed with the use of the commercially available finite element software ABAQUS® and were validated against the experimental observations. The effects of the lack of ductility of the shear connectors on the structural behaviour of the entire composite beam was examined with different types of shear connectors, shear connector layouts and material grades. This contribution presents the underlying laboratory tests as well as the results of the supplementing numerical parameter studies. The outcome provides valuable information for future design guidance concerning the use of demountable shear connectors in composite beams. [less ▲]

Push-out tests on demountable shear connectors of steel concrete composite structures

in Structures (2019), 21

Circular Economy refers to a move from linear business models, in which products are manufactured from raw materials, used and then discarded, to circular business models where products or parts are re ... [more ▼]

Circular Economy refers to a move from linear business models, in which products are manufactured from raw materials, used and then discarded, to circular business models where products or parts are re-used, remanufactured or recycled. Structural steel is highly compatible with this concept; however, when steel-concrete composite structures are used, recycling becomes difficult and the potential for reuse is lost. In order to make steel-concrete composite structures reusable, bolted connections should replace the commonly used welded headed studs. Furthermore, the reusable parts should be designed to withstand repeated use. This paper presents a desktop study and the corresponding laboratory experiments on demountable shear connectors that facilitate recyclability and even provide the potential for reusing complete structural elements. In the Laboratory of Steel and Composite Structures of the University of Luxembourg 15 push-out tests have been carried out using different bolted connection systems suitable for multiple use. The shear connectors have been evaluated based on their shear strength, stiffness, slip capacity, ductility and ability of demounting. The investigated systems included pre-stressed and epoxy resin injection bolts, solid slabs and solid slabs in combination with profiled steel sheeting. The results showed that the tested demountable shear connections could provide higher shear resistance than conventional shear connections. The critical failure mode was the shear failure of the bolts, which is a brittle failure. There was no visible damage observed on the connected members. The application of epoxy resin in the hole clearance resulted in lower slip capacity. The outcome provides an important basis for the justification of the forthcoming enhancement and validation of numerical models of the demountable shear connections. The failure behaviour, the observed damages and the resulting ability of the elements for re-use are discussed in detail. [less ▲]

Push-out tests on demountable shear connectors of steel-concrete composite structures

in Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures (2018, June 27)

The deconstruction of steel-concrete composite structures in buildings and the later separation of the materials is a labour- and cost intensive work. The shear studs are welded on the steel beam and ... [more ▼]

The deconstruction of steel-concrete composite structures in buildings and the later separation of the materials is a labour- and cost intensive work. The shear studs are welded on the steel beam and imbedded in the concrete deck and a large amount of cutting work becomes necessary. As a result, recycling is difficult and the potential for reusing entire elements is lost. The carbon footprint of composite structures could be decreased by application of the principles of “design for deconstruction and reuse”. This paper presents a desk top study and corresponding laboratory experiments on demountable shear connectors that facilitate recyclability and even provide the potential for reusing complete structural elements. In the Laboratory of Steel and Composite Structures of the University of Luxembourg 15 push-out tests have been carried out using different bolted connection systems suitable for multiple uses in order to verify their performance focusing on shear strength, stiffness, slip capacity, ductility and ability of demounting. The investigated systems included pre-stressed and epoxy resin injection bolts, solid slabs and composite slabs with profiled decking. The results showed that the tested demountable shear connections could provide higher shear resistance than conventional shear connections. The critical failure mode is shear failure of the bolts, while there was no visible damage observed on the connected members. Most of the tested connections could fulfil the ductility requirement according to by Eurocode 4. The application of epoxy resin in the hole clearance resulted in lower slip capacity. The outcome provides an important basis for the justification of the forthcoming enhancement and validation of numerical models of the demountable shear connections. The failure behaviour, the observed damages and the resulting ability of the elements for re-use are discussed in detail. [less ▲]