Finite element analysis of concrete filled lean duplex stainless steel columns

YesIn recent years, a new low nickel content stainless steel (EN 1.4162) commonly referred as ‘lean duplex stainless steel’ has been developed, which has over two times the tensile strength of the more familiar austenitic stainless steel but at approximately half the cost. This paper presents the finite element analysis of concrete filled lean duplex stainless steel columns subjected to concentric axial compression. To predict the performance of this form of concrete filled composite columns, a finite element model was developed and finite element analyses were conducted. The finite element model was validated through comparisons of the results obtained from the experimental study. A parametric study was conducted to examine the effect of various parameters such as section size, wall thickness, infill concrete strength, etc. on the overall behaviour and compressive resistance of this form of composite columns. Through both experimental and numerical studies, the merits of using lean duplex stainless steel hollow sections in concrete filled composite columns were highlighted. In addition, a new formula based on the Eurocode 4 was proposed to predict the cross-section capacity of the concrete filled lean duplex stainless steel composite columns subjected to axial compression

Experimental study of beam to concrete-filled elliptical steel tubular column connections

YesThis paper investigated the rotation behaviour of simply bolted I-beam to concrete-filled elliptical steel tubular (CFEST) column connections experimentally. Ten different joint assemblies were tested to failure, with a constant axial compressive load applied to the column and upwards concentrated loads at the beam ends. All of the steel tubes were hot-finished and had a cross-sectional aspect ratio of 2. The orientation of the column and the arrangement of the stiffening plates were taken into consideration. Moment versus rotation relationships and failure modes were compared for each joint, highlighting the benefits of using core concrete and stiffeners in these connections

Finite element analysis on the capacity of circular concrete-filled double-skin steel tubular (CFDST) stub columns

YesThis paper presents the behaviour of circular concrete-filled double-skin steel tubular (CFDST) stub columns compressed under concentric axial loads. To predict the performance of such columns, a finite element analysis is conducted. Herein, for the accurate modelling of the double-skin specimens, the identification of suitable material properties for both the concrete infill and steel tubes is crucial. The applied methodology is validated through comparisons of the results obtained from the finite element analysis with those from past experiments. Aiming to examine the effect of various diameter-to-thickness (D/t) ratios, concrete cube strengths and steel yield strengths on the overall behaviour and ultimate resistance of the double-skin columns, a total of twenty-five models are created to conduct the parametric study. In addition, four circular concrete-filled steel tubes (CFST) are included to check the dissimilarities, in terms of their behaviour and weight, when compared with identical double-skin tubes. A new formula based on Eurocode 4 is proposed to evaluate the strength of the double-skin specimens. Based on the comparison between the results derived from the analysis, the proposed formulae for the concrete filled double-skin would appear to be satisfactory

Structural behaviour of beam to concrete-filled elliptical steel tubular column connections

YesElliptical Hollow Sections (EHSs) have been utilized in construction recently because of their visual appearance as well as the potential structural efficiency owing to the presence of the two principle axes. However, little information currently exists for the design of beam to elliptical column connections, which is an essential part of a building structure. Thus, to ensure the safe and economic application of EHSs, a new research project has been initiated. Rotation behaviour of simply bolted beam to concrete-filled elliptical steel column connections was investigated experimentally. Various joint types were considered and the benefits of adopting core concrete and stiffeners were highlighted. This paper covers the experimental studies and simulation of the connections using the ABAQUS standard solver. Comparisons of failure modes and moment vs. rotation relationships of the connections between numerical and experimental results were given. Good agreement has been obtained and the developed finite element model was therefore adopted to conduct a preliminary parametric study to explore the effect of critical parameters on the structural behaviour of beam to concrete-filled elliptical column connections

Experimental study on demountable shear connectors in profiled composite slabs

[EN] This paper presents an experimental study on demountable shear connectors in profiled composite slabs. Overall, three groups of push-off tests were conducted to assess the shear capacity, stiffness and ductility of the shear connectors. In all the specimens, a pair of shear studs were used per trough and were bolted to each side of the flange of a loading beam. Different concrete strength, embedment height of the shear studs and reinforcement cage were considered. Particularly, a joint was made between the pair studs in two groups of specimens when casting and formed two completely separate slabs per half specimen, to evaluate the load transfer between the pair studs. The experimental results showed that the shear capacity and behavior of the demountable connectors in separate slabs and continuous slab were both similar to the welded connectors and could fulfill the 6mm minimum ductility requirement stated in Eurocode 4 if proper embedment height of connector was used. The shear capacities of the tested specimens were compared against the calculated results obtained from the equations used for welded shear connectors in Eurocode 4 and bolted connections in Eurocode 3. Generally, the Eurocodes prediction underestimated the shear capacities of the push-off specimens.The research leading to these results is part of a joint project of the University of Bradford and University of Manchester and it has received funding from Engineering and Physical Sciences Research Council (EPSRC, EP/N011201/1).Yang, J.; Lam, D.; Dai, X.; Sheehan, T. (2018). Experimental study on demountable shear connectors in profiled composite slabs. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 115-121. https://doi.org/10.4995/ASCCS2018.2018.6959OCS11512

Tests of self-compacting concrete filled elliptical steel tube columns

YesThis paper presents an experimental study into the axial compressive behaviour of self-compacting concrete filled elliptical steel tube columns. In total, ten specimens, including two empty columns, with various lengths, section sizes and concrete strengths were tested to failure. The experimental results indicated that the failure modes of the self-compacting concrete filled elliptical steel tube columns with large slenderness ratio were dominated by global buckling. Furthermore, the composite columns possessed higher critical axial compressive capacities compared with their hollow section companions due to the composite interaction. However, due to the large slenderness ratio of the test specimens, the change of compressive strength of concrete core did not show significant effect on the critical axial compressive capacity of concrete filled columns although the axial compressive capacity increased with the concrete grade increase. The comparison between the axial compressive load capacities obtained from experimental study and prediction using simple methods provided in Eurocode 4 for concrete-filled steel circular tube columns showed a reasonable agreement. The experimental results, analysis and comparison presented in this paper clearly support the application of self-compacting concrete filled elliptical steel tube columns in construction engineering practice

Use of bolted shear connectors in composite construction

[EN] Composite beam incorporated steel profiled decking has been extensively used for multi-storey buildings and is now one of the most efficient and economic form of flooring systems. However, the current composite flooring system is not demountable and would require extensive cutting on site during demolition, and the opportunity to reuse the steel components is lost even though these components could be salvaged and recycled. This paper presents the use of high strength bolts as shear connectors in composite construction, the shear behaviour and failure modes were observed and analysed through a series of push-off tests and numerical simulation. The results highlighted the structural behaviour of three different demountable shear connection forms in which continuous slabs or un-continuous slabs were used. Numerical models were validated against experimental observation. Both experimental and numerical results support the high strength bolts used as demountable shear connectors and lead to a better understanding to the behaviour of this form of shear connectors.The research leading to these results is part of a joint project of the Steel Construction Institute, the University of Luxembourg, the University of Bradford, the Lindab SA, the Tata Steel Ijmuiden BV, the Stichting Bouwen Met Staal, the Technical University of Delft and the AEC3 Ltd. The funding was received from the European Commission: Research Fund for Coal and Steel (RFCS-2015, RPJ, 710040).Dai, X.; Lam, D.; Sheehan, T.; Yang, J.; Zhou, K. (2018). Use of bolted shear connectors in composite construction. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 475-482. https://doi.org/10.4995/ASCCS2018.2018.7039OCS47548

Flexural behaviour of composite slim floor beams

[EN] Composite slim floor beams comprise a steel section embedded in a concrete slab, offering the advantages of a steel-concrete composite structure combined with a reduced floor depth. Several mechanisms contribute to the shear connection in this type of beam, such as headed studs, friction and clamping effects and the using of reinforcement bars passing through holes in the steel beam web. However, to date, nobody has systematically identified these mechanisms and Eurocode 4 does not provide specific design guidance for slim floor beams. Hence, a series of shear beam tests and flexural beam tests were carried out in order to assess the degree of shear connection and connector capacity in these beams. The test set-up is described including different arrangements of shear connectors for each specimen. The paper presents the findings from the flexural beam tests. The results are compared with those from the previous shear beam tests. Numerical models will be developed in future to extend the data and include a wider range of parameters. The data will also be used to improve understanding of this type of beam and will lead to the provision of specific design guidelines for slim floor beams.The authors gratefully acknowledge the funding received from the European Community Research Fund for Coal and Steel under grant agreement number RFSR-CT-2015-00020.Sheehan, T.; Dai, X.; Yang, J.; Zhou, K.; Lam, D. (2018). Flexural behaviour of composite slim floor beams. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 137-144. https://doi.org/10.4995/ASCCS2018.2018.6963OCS13714

Flexural behaviour of asymmetric composite beam with low degree of shear connection

YesThis paper outlines an experiment on a 12 m long composite beam subjected to uniformly distributed loading. Although composite beams are widely used, current Eurocode design guidelines for these types of members can be over-conservative, particularly in relation to the required degree of shear connection. The tested beam comprised a concrete slab supported by profiled metal decking, connected to an asymmetric fabricated steel I-beam using welded shear studs. The specimen was assembled using unpropped construction methods and had a degree of shear connection equal to 33%, significantly lower than the minimum required amount specified in Eurocode 4. A uniformly distributed load was applied to the specimen, which was increased until the failure occurred characterized by yielding of the steel beam. The maximum bending moment of the composite beam obtained from the test was close to the plastic bending resistance according to the Eurocode 4. No concrete crushing or shear stud failure was observed and the end slips exceeded 6 mm, the limit for ductile behaviour in Eurocode 4. The test demonstrated the merits of unpropped construction, which are currently not fully exploited in Eurocode 4. The comparison and analysis suggest that the design limits governing the minimum degree of shear connection might be revised.RFC

Experimental study on long spanning composite cellular beam under flexure and shear

YesThis paper describes a sequence of experiments on a long-span asymmetric composite cellular beam. This type of beam has become very popular, combining the composite action between the steel and concrete with the increased section depth, compared with more commonly used solid-web I sections. Openings in the steel web also reduce the self-weight and can accommodate the passage of service ducts. Eurocode 4 recommends a high degree of shear connection for asymmetric composite beams despite the practical difficulties in achieving this. Recent research suggests that the required degree of shear connection could be reduced, particularly for beams that are unpropped during construction. However, little test data exists to verify the behaviour of unpropped composite cellular beams. Therefore two series of tests were conducted on a 15.26 m long asymmetric composite cellular beam with regular circular openings and an elongated opening at the mid-span. The degree of shear connection was 36%, less than half of that recommended in Eurocode 4, and the beam was unpropped during construction. The beam was subjected to uniformly distributed loading and shear load during the tests. The end-slip, mid-span vertical deflection, shear connector capacity and strain distribution were examined. The beam failed at an applied uniform load of 17.2 kN/m2 (3.4 × design working load 5.0 kN/m2). The member withstood an applied shear load that was 45% higher than predicted, and exhibited a Vierendeel mechanism at the elongated opening. Overall, these tests demonstrated the potential of unpropped composite cellular beams with low degrees of shear connection.RFC