Imperial College London

DrPinelopiKyvelou

Faculty of EngineeringDepartment of Civil and Environmental Engineering

Research Associate
 
 
 
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Contact

 

pinelopi.kyvelou11

 
 
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Location

 

Skempton BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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24 results found

Kyvelou P, Nethercot D, Hadjipantelis N, Kyprianou C, Gardner Let al., 2020, The evolving basis for the design of light gauge steel systems, International Journal of Structural Stability and Dynamics, ISSN: 0219-4554

The importance of allowing for the many different types of structural interaction that have aneffect on the performance of light gauge members when used in practical situations isemphasised. A distinction is drawn between internal interactions involving the various plateelements of the steel profiles and external interactions involving the other components in thesystem. Although full-scale testing of representative systems can capture this behaviour, thecosts involved make this an impractical general basis for design; codified methods generallyconsider only isolated plates within members and isolated members within systems, therebyneglecting the potentially beneficial effects of both forms of interaction. Properly used,modern methods of numerical analysis offer the potential to systematically allow for bothforms of interaction – provided the numerical models used have been adequately validatedagainst suitable tests. The use of such an approach is explained and illustrated for threecommonly used structural systems: roof purlins, floor beams and columns in stud walls. Ineach case it is shown that, provided sufficient care is taken, the numerical approach can yieldaccurate predictions of the observed test behaviour. The subsequently generated largeportfolio of numerical results can then provide clear insights into the exact nature of thevarious interactions and, thus, form the basis for more realistic design approaches that areboth more accurate in their predictions and which lead to more economic designs. Buildingon this, modifying existing arrangements so as to yield superior performance through specificmodifications is now possible. Two such examples, one in which improved interconnectionbetween the components in a system is investigated and a second in which prestressing isshown to provide substantial enhancement for relatively small and simple changes, arepresented.

Journal article

Gardner L, Kyvelou P, Herbert G, Buchanan Cet al., Testing and initial verification of the world's first metal 3D printed bridge, Journal of Constructional Steel Research, ISSN: 0143-974X

Journal article

Kyvelou P, Slack H, Daskalaki Mountanou D, Wadee MA, Britton T, Buchanan C, Gardner Let al., 2020, Mechanical and microstructural testing of wire and arc additivelymanufactured sheet material, Materials and Design, Vol: 192, ISSN: 0264-1275

Wire and arc additive manufacturing (WAAM) is a method of 3D printing that enables large elements to be built, with reasonable printing times and costs. There are, however, uncertainties relating to the structural performance of WAAM material, including the basic mechanical properties, the degree of anisotropy, the influence of the as-built geometry and the variability in response. Towards addressing this knowledge gap, a comprehensive series of tensile tests on WAAM stainless steel was conducted; the results are presented herein. As-built and machined coupons were tested to investigate the influence of the geometrical irregularity on the stress-strain characteristics, while material anisotropy was explored by testing coupons produced at different angles to the printing orientation. Non-contact measurement techniques were employed to determine the geometric properties and deformation fields of the specimens, while sophisticated analysis methods were used for post processing the test data. The material response revealed a significant degree of anisotropy, explained by the existence of a strong crystallographic texture, uncovered by means of electron backscatter diffraction. Finally, the effective mechanical properties of the as-built material were shown to be strongly dependent on the geometric variability; simple geometric measures were therefore developed to characterise the key aspects of the observed behaviour.

Journal article

Gardner L, Buchanan C, Kyvelou P, Herbert Get al., 2019, TESTING AND VERIFICATION OF THE WORLD’S FIRST METAL 3D PRINTED BRIDGE, 9th International Conference on Steel and Aluminium Structures (ICSAS19)

Conference paper

Kyvelou P, Gardner L, Nethercot DA, 2019, Impact statement on “Design of composite cold-formed steel flooring systems”, Structures, Vol: 20, Pages: 213-213, ISSN: 2352-0124

Journal article

Kyvelou P, Kyprianou C, Gardner L, Nethercot DAet al., 2019, Challenges and solutions associated with the simulation and design of cold-formed steel structural systems, Thin-Walled Structures, Vol: 141, Pages: 526-539, ISSN: 0263-8231

The treatment of cold-formed steel sections in design codes is very largely restricted to individual members under ideal conditions. More efficient design is possible if the complexities of the structural response caused by the thin plating and complex shapes, together with the actual conditions of load introduction and restraint arising from practical situations can be recognised. Traditionally this has only been possible by resorting to full-scale testing. This is, of course, time consuming and expensive; moreover, the impossibility of covering all variations of all the important problem parameters means that developing a comprehensive understanding of all aspects of the physical behaviour is unlikely. Numerical analysis offers the promise of an alternative approach. However, for this to be reliable there must be confidence that it accurately models the physical situation. For the past decade a programme of research has been underway aimed at the provision of a more complete understanding of the structural behaviour of cold-formed steel sections when employed in particular practical situations. Three such cases are addressed herein: purlins as used in the roofs of industrial buildings, beams used to support floors and columns forming part of a stud wall framing system. In each case the process has been to firstly identify all the important structural components including fastening arrangements, then to develop numerical models using ABAQUS that represent each of these physical features to a sufficient degree of accuracy, then to validate the models by comparison with all available test data, then to conduct parametric studies covering the full range of variables found in practice and, finally, to use the pool of results and the improved insights into behaviour as the basis for improved design approaches that, by more accurately capturing the key physical features, provide better predictions of performance. An important feature of this has been to ensure that the r

Journal article

Hadjipantelis N, Kyvelou P, Gardner L, Wadee Met al., 2019, Numerical modelling of prestressed composite cold-formed steel flooring systems, Seventh International Conference in Structural Engineering, Mechanics and Computation, Publisher: CRC Press

A novel and highly-efficient prestressed composite flooring system comprising cold-formed steel joists and wood-based floorboards is introduced herein. The prestressing is applied by means of a high-strength steel cable housed within the bottom hollow flange of the steel joist, while the composite action is mobilised by making simple alterations to the currently employed fastening arrangements between the joist and the board. Geometrically and materially nonlinear finite element models with initial geometric imperfections have been developed to simulate the behaviour of the proposed system during the prestressing and vertical loading stages. The structural performance of the prestressed system is compared with that of conventional non-prestressed systems, demonstrating that substantial benefits can be achieved both in terms of load-carrying capacity and serviceability performance. Subsequently, a parametric study is conducted to investigate the effect of the steel section thickness on the ultimate moment capacity and bending stiffness of the system.

Conference paper

Kyvelou P, Gardner L, Nethercot D, 2019, Testing and analysis of shear connectors between cold-formed steel members and wood-based panels, THE SEVENTH INTERNATIONAL CONFERENCE ON STRUCTURAL ENGINEERING, MECHANICS AND COMPUTATION, SEMC2019

Conference paper

Kyvelou P, Hui C, Gardner L, Nethercot DAet al., 2018, Moment redistribution in cold-formed steel sleeved and overlapped two-span purlin systems, Advances in Structural Engineering, Vol: 21, Pages: 2534-2552, ISSN: 1369-4332

Cold-formed steel purlin systems with overlapped or sleeved connections are alternatives to continuous two-span systems and exhibit different degrees of continuity. Both connection types are highly favourable in practice since they are both strategically placed over an interior support to provide additional moment resistance and rotational capacity where the corresponding demands are at their largest, thus improving the overall structural efficiency. Until recently, full-scale testing has been the most common way of investigating the structural behaviour of such systems. In this study, numerical modelling, capable of capturing the complex contact interactions and instability phenomena, is employed. The developed finite element models are first validated against data from physical tests on cold-formed steel beams featuring sleeved and overlapped connections that have been previously reported in the literature. Following their validation, the models are employed for parametric studies, based on which the structural behaviour of the examined systems is explored, while the applicability of conventional plastic design as well as of a previously proposed design approach is investigated. Finally, the efficiency of these systems in terms of load-carrying capacity is compared with their equivalent continuous two-span systems.

Journal article

Nethercot D, Kyvelou P, Gardner L, Kyprianou Cet al., 2018, DESIGNING COLD- FORMED STEELWORK AS STRUCTURAL SYSTEMS, 25th Australasian Conference on Mechanics of Structures and Materials, ACMSM25

Conference paper

Kyprianou C, Kyvelou P, Gardner L, Nethercot Det al., 2018, NUMERICAL STUDY OF SHEATHED COLD-FORMED STEEL COLUMNS, Ninth International Conference on Advances in Steel Structures (ICASS’2018)

Conference paper

Kyvelou P, Gardner L, Nethercot D, 2018, Moment redistribution in cold-formed steel two-span overlapped purlin systems, Eighth International Conference on Thin-Walled Structures, ICTWS 2018

Conference paper

Kyvelou P, Gardner L, Nethercot D, 2018, Moment Redistribution in Cold-Formed Steel Two-Span Overlapped Purlin Systems, 8th International Conference on Thin-Walled Structures, ICTWS 2018

Conference paper

Kyvelou P, Reynolds T, Beckett C, Wong PW, Huang Yet al., 2018, Composite Panels of Cold-Formed Steel and Timber for High-Density Construction, 2018 World Conference on Timber Engineering, WCTE 2018

Conference paper

Kyvelou P, Gardner L, Nethercot DA, 2017, Finite element modelling of composite cold-formed steel flooring systems, Engineering Structures, Vol: 158, Pages: 28-42, ISSN: 0141-0296

The findings from a numerical investigation into the degree of composite action that may be mobilised within floor systems comprising cold-formed steel joists and wood-based particle boards are presented herein. Finite element models have been developed, simulating all the components of the examined systems, as well as the interaction between them. The models include initial geometric imperfections, the load-slip response of the fasteners employed to achieve the shear connection as well as both geometric and material nonlinearities. The developed models were first validated against 12 physical tests reported in the literature, which showed them to be capable of accurately capturing the load-deformation curves and failure modes exhibited by the tested specimens. Parametric studies were then performed to examine the influence of key parameters on the structural behaviour of these systems, including the depth and thickness of the cold-formed steel section, as well as the spacing of the employed fasteners; in total, about 100 systems have been examined. Significant benefits in terms of structural response have been identified from the presented numerical study as a result of the mobilisation of composite action; for the systems investigated, which were of typical, practical proportions, up to 140% increases in moment capacity and 40% increases in stiffness were found. The presented research reveals the substantial gains in structural performance and the influence of the key governing parameters for this novel form of composite construction.

Journal article

Kyvelou P, Gardner L, Nethercot DA, 2017, Design of composite cold-formed steel flooring systems, Structures, Vol: 12, Pages: 242-252, ISSN: 2352-0124

Recently conducted experimental and numerical investigations have shown that mobilisation of composite action within systems comprising cold-formed steel beams and wood-based floorboards is feasible and can lead to substantial improvements in structural performance. However, no design rules have yet been established for these systems in order to allow the beneficial effect of composite action to be exploited. In this paper, proposals for the design of such systems are devised and their theoretical basis is presented. At the core of the proposals is the calculation of the attained degree of partial shear connection and the shear bond coefficient for the composite members as a function of the geometric and material properties of their components and connectors. The accuracy of the devised design method for the prediction of moment capacity and flexural stiffness is demonstrated through comparisons with the results of 12 physical tests and about 80 numerical simulations reported in the literature. The proposals provide practical design rules for composite cold-formed steel floor beams, which are suitable for incorporation into future revisions of the Eurocodes.

Journal article

Kyvelou P, Gardner L, Nethercot D, 2017, Design of cold-formed steel composite flooring systems with partial shear connection, 8th European Conference on Steel and Composite Structures (Eurosteel 2017), Pages: 1899-1908

Conference paper

Kyvelou P, Gardner L, Nethercot D, 2017, Utilising Composite Action in Light Steel Framing, 15th East Asia Pacific Conference on Structural Engineering and Construction, EASEC15

Conference paper

Kyvelou P, Gardner L, Nethercot DA, 2017, Testing and Analysis of Composite Cold-Formed Steel and Wood-Based Flooring Systems, Journal of Structural Engineering, Vol: 143, ISSN: 0733-9445

An experimental study was conducted into the degree of composite action that can arise between cold-formed steel joists and wood-based flooring panels. A series of material, push-out and 4-point bending tests were carried out, and alternative means of shear connection, featuring fasteners and adhesives, were investigated. It was found that the spacing of the fasteners and the application of structural adhesive at the beam-board interface had a significant influence on the attained degree of shear connection and, hence, the moment capacity and flexural stiffness of the system. The highest degree of shear connection (up to approximately 60%) was obtained using the structural adhesive, bringing corresponding increases in capacity and stiffness of approximately 100 and 40%, respectively, over the bare steel. Smaller, but still very significant, increases in capacity and stiffness were achieved through the use of screws alone. On the basis of the results of the push-out tests, a load-slip relationship for screw fasteners in wood-based floorboards was proposed; this was designed for use in future analytical and numerical models. The findings of this research demonstrate, for the first time, the benefits that can be derived through the practical exploitation of composite action in cold-formed steel flooring systems in terms of enhanced structural performance and efficiency of material use.

Journal article

Kyvelou P, Gardner L, Nethercot D, 2017, Design of Cold-Formed Steel Composite Flooring Systems with Partial Shear Connection, 8th European Conference on Steel and Composite Structures, Eurosteel 2017

Conference paper

Kyvelou P, Gardner L, Nethercot DA, 2016, COMPOSITE FLOORING SYSTEMS COMPRISING COLD-FORMED STEEL JOISTS AND WOOD-BASED BOARDS, 8th International Conference on Steel and Aluminium Structures (ICSAS), Publisher: UNIV HONG KONG, DEPT CIVIL ENGINEERING

Conference paper

Kyvelou P, Gardner L, Nethercot DA, 2015, Composite Action Between Cold-Formed Steel Beams and Wood-Based Floorboards, International Journal of Structural Stability and Dynamics, Vol: 15, ISSN: 1793-6764

An experimental investigation has been conducted into the degree of shear interaction between cold-formed steel floor joists and wood-based flooring panels and the resulting benefits derived in terms of composite action. A series of four-point bending tests have been carried out to evaluate the overall system behavior, while material tests have been performed to accurately define the material properties of each component of the examined system. Two different shear transfer mechanisms were examined: self-drilling screws with varying spacing and structural adhesive. The bare system was also tested to provide a reference response, against which the stiffness and capacity of the composite system could be bench-marked. The experiments showed that significant benefit could be derived as a result of composite action with as much as a 100% increase in bending capacity and 42% increase in stiffness.

Journal article

Nethercot D, Kyvelou P, Hui C, Gardner Let al., 2015, The changing basis for the design of cold-formed steel purlin systems, Eighth International Conference on Advances in Steel Structures (ICASS)

Conference paper

Kyvelou P, Gardner L, Nethercot DA, 2015, Composite action between cold-formed steel beams and wood-based floorboards, Eighth International Conference on Advances in Steel Structures (ICASS)

Conference paper

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