Naslov
Innovative lightweight composite floor system – built-up cold formed steel-concrete

Autori
Rajić, Andrea ; Lukačević, Ivan ; Ćurković, Ivan ; Žuvelek, Vlaho

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Modern structures of metal and wood - Book of Abstract / - Odesa : Ministry of Education and Science of Ukraine ; Odesa State Academy of Civil Engineering and Architecture Rzeszów ; University of Technology (Poland) ; University of Rijeka (Croatia), 2022, 18-20

Skup
International Scientific and Technical Conference Modern structures of metal and wood

Mjesto i datum
Odesa, Ukrajina, 09.06.2022. - 11.06.2022

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Composite beams ; Cold-formed Steel Sections ; Bending Resistance

Sažetak
With the intention of increasing the advantages of composite steel-concrete systems, the cold-formed steel (CFS) profiles have been used. In this way, the weight of the whole system has been reduced. Additionally, combining two different materials, such as CFS and concrete, can avoid their inherent disadvantages. The main advantages of composite beams are: - weight savings of steel between 30-50%, compared to non-composite beams, - increased stiffness can result in the reduction of beam height, - reduction of cladding costs, - allowing more space for mechanical services. The research project Innovative lightweight cold- formed steel-concrete composite floor system - LWT-FLOOR, ongoing at the University of Zagreb, Faculty of Civil Engineering, Croatia, investigates a composite floor system that offers benefits in terms of reusability and a high degree of prefabrication. The LWT-FLOOR system is formed from built-up steel beams and cast-in-place concrete slab connected by innovative shear connection. Innovative demountable shear connection is one of the main advantages of the proposed system and is used to decrease the impact on the environment. A built-up CFS beam is composed of four cold-formed C sections connected by spot welds with corrugated web (CW) and shear plates. Due to the relatively small thickness of CW, weight reduction is allowed compared to hot-rolled profiles or welded I sections. The advantage of this type of built-up beam is that CW increases stability against local and lateral-torsional buckling and web crippling. Experimental research within the LWT-FLOOR project is divided into five phases: - experimental research of base material, - experimental research of spot welds between CFS sections, - experimental tests of shear connection, - experimental tests of full-scale LWT-FLOOR system without openings, - experimental tests of full-scale LWT-FLOOR system with openings. As an extension of experimental research, the proposed system will be evaluated through extensive numerical and probabilistic parametric studies and life-cycle analyses. This report presents results of preliminary numerical research on the LWT-FLOOR system with a different arrangement of spot welds in CFS cross- section (two or three spot welds) and variable degrees of shear connection. Numerical research was conducted using ABAQUS/CAE software. To support numerical results, analytical results were also provided. Considering that CFS sections are usually class 3 and 4, their plastic resistance is possible to achieve only in the cases with the plastic neutral axis in the concrete slab or on the contact between the concrete slab and steel section. In that case, the steel cross-section will be completely or almost completely in tension. Because of the mentioned situation, local instability will be avoided, and bending resistance can be calculated. Because of a large number of nonlinearities in the model (geometry, material, contacts), dynamic explicit analysis is used. Initial imperfections were created through static analyses of the system with fully tied elements. In this way, the imperfection shape has been achieved with required displacement. The load was set as a vertical displacement in multipoint constraints (MPC) that transfer the load onto four loading points. Used characteristics for spot welds were used from results of tensile shear test given in available literature, while wire elements were used to model the shear connectors. The presented LWT-FLOOR project integrates state- of-the-art knowledge in a new and productive spot welding technology and innovative cold-formed steel–concrete composite solutions to develop a cost-effective and competitive floor system. The LWT-FLOOR system can give vital benefits in terms of a high degree of prefabrication, reusability and suitability for larger spans to maximise the values of building components and materials. The proposed analytical solution for bending resistance of composite cross-section is based on the elastic bending resistance of steel beams. The numerical parametric FE analyses show that the bending capacity of the LWT-FLOOR beams made of cold-formed steel and the cast-in-place concrete slab can be compared with analytical results. Results of the parametric FE study show that the bending capacity of the LWT-FLOOR beams made of cold-formed steel and the cast-in-place concrete slab is affected by the resistance of the cold- formed steel components and by the degree of shear connection. In the case of a fixed beam solution, the resistance of the LWT-FLOOR beam is governed by the resistance of the steel beam, i.e., spot welds. In the cases with pinned beam solution, the results show that the resistance of the LWT-FLOOR beam is governed by the degree of shear connection. At the same time, the increased number of spot welds from two to three between channel flanges and corrugated web does not influence the beam resistance. This means that the beam resistance in the pinned solution is rather more affected by the stability of the cold-formed steel components than the number of spot welds, with a significant influence on the type and degree of shear connection. Funding: This work has been supported in part by Croatian Science Foundation under the project UIP-2020-02- 2964.

Izvorni jezik
Engleski

Znanstvena područja
Građevinarstvo

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