Imperial College London

Emeritus ProfessorDavidNethercot

Faculty of EngineeringDepartment of Civil and Environmental Engineering

Senior Research Investigator
 
 
 
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Contact

 

+44 (0)20 7594 6097d.nethercot

 
 
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Location

 

306Skempton BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

592 results found

Nethercot DA, 2021, Professor Nicholas Trahair, ENGINEERING STRUCTURES, Vol: 244, ISSN: 0141-0296

Journal article

Wang K, Xiao M, Chung K-F, Nethercot DA, Wang K, Xiao M, Chung K-F, Nethercot DAet al., 2021, Lateral torsional buckling of partially restrained beams of high strength S690 welded I-sections, JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, Vol: 184, ISSN: 0143-974X

Journal article

Kyprianou C, Kyvelou P, Gardner L, Nethercot Det al., 2021, Experimental study of sheathed cold-formed steel beam-columns, Thin Walled Structures, Vol: 166, ISSN: 0263-8231

An experimental study of sheathed cold-formed steel C-lipped wall studs, with service holes, subjected to compression and major axis bending is presented in this paper. A total of 17 experiments were performed with both oriented strand board (OSB) and plasterboard used as sheathing and with varying connector spacing employed between the sheathing panels and the steel members. The tested specimens comprised a single 2.4 m long column sheathed on both sides and secured at the ends to top and bottom tracks. The member tests were complemented by material tests, stub column tests and initial geometric imperfection measurements. The specimens were tested in a dual-actuator rig where axial compression was applied by means of a vertical actuator through the top track, while bending was applied through the application of four lateral point loads. Eight pure compression tests with both plasterboard and OSB sheathing and with the spacing of the connectors varying between 75 mm and 600 mm were initially performed. Specimens with OSB sheathing were then tested under pure bending and combined loading. The full load–deformation responses and failure modes of the member test specimens are reported. The compressed studs connected to the plasterboard sheathing at wider spacings exhibited pull-through failure of the connectors, followed by flexural torsional buckling, while the specimens with denser connector spacings, failed by local buckling at the member ends. The OSB sheathed specimens under pure compression failed by local and distortional buckling, those under combined loading exhibited local failure at the service openings, while for those under pure bending, local buckling and stud-to-track connector failure occurred. Reducing the spacing of the connectors from 600 mm to 75 mm resulted in up to 20% and 30% increases in capacity for the studs sheathed with OSB and plasterboard respectively.

Journal article

Hu Y-F, Chung K-F, Jin H, Ban H, Nethercot DAet al., 2021, Structural behaviour of T-joints between high strength S690 steel cold-formed circular hollow sections, JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, Vol: 182, ISSN: 0143-974X

Journal article

Kyprianou C, Kyvelou P, Gardner L, Nethercot DAet al., 2021, Characterisation of material and connection behaviour in sheathed cold-formed steel wall systems - Part 1: Experimentation and data compilation, STRUCTURES, Vol: 30, Pages: 1161-1183, ISSN: 2352-0124

Journal article

Kyprianou C, Kyvelou P, Gardner L, Nethercot Det al., 2021, Characterisation of material and connection behaviour in sheathed cold-formed steel wall systems - Part 2: analytical modelling, Structures, Vol: 30, Pages: 1184-1199, ISSN: 2352-0124

Analytical models to describe the material and connection behaviour of the key components of sheathed cold-formed steel wall systems are developed and assessed in the present paper. The experimental data generated and collected in the companion paper (Kyprianou et al. [1]) are utilised for the calibration of the developed models. The assembled experimental database comprises the results of more than 400 physical tests, featuring material tests on plasterboard and oriented strand board (OSB), screw connector tests as well such as pull-through and push-out tests. The Ramberg–Osgood model (Ramberg and Osgood [2]) was shown to accurately describe the stress–strain behaviour of both plasterboard and OSB in the longitudinal and transverse direction in both tension and compression, while the Mander model (Mander et al. [3]) was also shown to accurately capture the compression behaviour for both materials and to follow the post peak unloading response. A generalised Ramberg–Osgood curve with linear post-peak unloading was adopted for describing the pull-through load-deformation behaviour of screws in OSB and plasterboard, while a similar generalised Ramberg–Osgood formulation, but with different exponents for the initial and subsequent parts of the curve was shown to accurately capture the shear load-slip behaviour of screws in steel-to-board connections. Predictive expressions for the ultimate capacities and recommended values for the remaining model parameters are provided herein. The developed predictive models are suitable for use in numerical simulations and advanced design methods.

Journal article

Kyprianou C, Kyvelou P, Gardner L, Nethercot Det al., 2021, Characterisation of material and connection behaviour in sheathed cold-formed steel wall systems - Part 1: experimentation and datacompilation, Structures, ISSN: 2352-0124

The material and connection behaviour in sheathed cold-formed steel wall systems are investigated in the present paper through experimentation. A total of 103 material and component tests was performed, including six cold-formed steel tensile coupon tests, nine tests on screws in tension, nine tests on screws in shear, 36 material tests on plasterboard and orientated strand board (OSB), 25 pull-through connection tests and 18 push-out (shear) connection tests. The plasterboard and oriented strand board were tested in both compression and tension, as well as both longitudinally and transversely to the production direction of the board. The main objective of the study was to measure and characterise the nonlinear response of all the materials and sheathing-to-steel connection components that are used in typical cold-formed steel wall systems, to support the ongoing and future development of accurate numerical simulations and structural design provisions for such systems. The present paper focuses on the experimental investigation and the collection of existing test data from the literature; a description of all the tests performed and a discussion of the results obtained are provided. The companion paper focuses on the establishment and assessment of predictive models to describe the responses of the material and connection components.

Journal article

Walport F, Gardner L, Nethercot D, 2021, Design of structural stainless steel members by second order inelastic analysis with CSM strain limits, Thin Walled Structures, Vol: 159, ISSN: 0263-8231

System-level advanced analysis is now a viable tool for widespread use in structuraldesign. By directly capturing frame and member level instability effects, plasticity, initialgeometric imperfections and residual stresses in the analysis, the need for subsequentindividual member checks can be eliminated. The analysis of structural members and framesis typically carried out using beam elements, which are unable to capture the effects of localbuckling. However, local buckling dictates the strength and ductility of cross-sections and theextent to which plastic redistribution of forces and moments can be exploited; it cannottherefore be disregarded. A proposal is made herein, in which strain limits, defined by thecontinuous strength method, are applied to simulate local buckling in beam element models,thereby controlling the degree to which spread of plasticity, force and moment redistributionand strain hardening can be utilised in the design of structural elements and systems. Strainsare averaged over a defined distance along the member length to reflect the fact that localbuckling requires a finite length over which to develop and to allow for local moment gradienteffects. Design is based directly on the application of strain limits to all cross-sections in thestructure. The accuracy of the proposed method for the design of stainless steel members isassessed through comparisons with benchmark shell finite element results; both I-section and hollow section members are considered. Comparisons against current design methods confirmthe significant benefits of applying the proposed approach in terms of both the accuracy andthe consistency of the resistance predictions. The reliability of the design approach isdemonstrated through statistical analyses performed in accordance with EN 1990. Applicationof the proposed method is particularly appropriate for stainless steel structures due to the highmaterial value and the complexities presented by the nonlinear material stress&

Journal article

Ho HC, Xiao M, Hu YF, Guo YB, Chung KF, Yam MCH, Nethercot DAet al., 2020, Determination of a full range constitutive model for high strength S690 steels, JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, Vol: 174, ISSN: 0143-974X

Journal article

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, Vol: 20, Pages: 1-40, 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

Hu Y-F, Chung K-F, Ban H, Nethercot DAet al., 2020, Investigations into residual stresses in S690 cold-formed circular hollow sections due to transverse bending and longitudinal welding, ENGINEERING STRUCTURES, Vol: 219, ISSN: 0141-0296

Journal article

Walport F, Gardner L, Nethercot D, 2020, Equivalent bow imperfections for use in design by second order inelastic analysis, Structures, Vol: 26, Pages: 670-685, ISSN: 2352-0124

The stability of compression members is typically assessed through buckling curves, which include the influence of initial geometric imperfections and residual stresses. Alternatively, the capacity may be obtained more directly by carrying out either an elastic or an in elastic second order analysis using equivalent bow imperfections that account for both geometric imperfections and residual stresses. For design by second order elastic analysis, following the recommendations of EN 1993-1-1, the magnitudes of the equivalent bow imperfections can either be back-calculated for a given member to provide the same result as would be obtained from the member buckling curves or can be taken more simply as a fixed proportion of the member length. In both cases, a subsequent M–N (bending + axial) cross-section check is also required, which can be either linear elastic or linear plastic. For design by second order inelastic analysis, also referred to as design by geometrically and materially nonlinear analysis with imperfections (GMNIA)there are currently no suitable recommendations for the magnitudes of equivalent bow imperfections and, as demonstrated herein, it is not generally appropriate to use equivalent bow imperfections developed on the basis of elastic analysis. Equivalent bow imperfections suitable for use in design by second order inelastic analysis are therefore establishedin the present paper.The equivalent bow imperfections are calibrated against benchmark FE results, generated using geometrically and materially nonlinear analysis with geometric imperfections of L/1000(L being the member length)and residual stresses. Based on the resultsobtained, an equivalent bow imperfection amplitude e0= L/150 ( being the traditional imperfection factor set out in EC3), isproposedfor both steel and stainless steel elements and shown to yield accurate results.The reliability of the proposed approach is assessed

Journal article

Ho H-C, Chung K-F, Huang M-X, Nethercot DA, Liu X, Jin G, Wang G-D, Tian Z-Het al., 2020, Mechanical properties of high strength S690 steel welded sections through tensile tests on heat-treated coupons, JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, Vol: 166, ISSN: 0143-974X

Journal article

Chung K-F, Ho H-C, Hu Y-F, Wang K, Liu X, Xiao M, Nethercot DAet al., 2020, Experimental evidence on structural adequacy of high strength S690 steel welded joints with different heat input energy, ENGINEERING STRUCTURES, Vol: 204, ISSN: 0141-0296

Journal article

Walport F, Gardner L, Nethercot DA, 2020, A method for the treatment of 2<sup>nd</sup> order effects in plastically-designed steel frames

The susceptibility of steel frames to global second order effects, also referred to as sway effects, 'P-∆' effects and global geometric nonlinearities, is traditionally assessed through the elastic buckling load factor αcr. For elastic analysis, EN 1993-1-1 and other international steel design standards deem second order effects sufficiently small that they may be ignored if the amplification of internal forces and moments is no more than 10% of the original forces and moments, corresponding to a limit of αcr≥10. For plastic analysis, to reflect the influence of the degradation of material stiffness, a stricter limit of 15 is prescribed for second order effects to be neglected. Use of a single limit of 15 for any structural system no matter the degree of influence of plasticity is considered by the authors to be overly simplistic. A parametric investigation to assess the stability of steel frames in the plastic regime is presented herein. Based on the findings, an improved method is proposed for the treatment of global second order effects in plastically-designed steel frames.

Conference paper

Walport F, Gardner L, Nethercot DA, 2019, A method for the treatment of second order effects in plastically-designed steel frames, Engineering Structures, Vol: 200, Pages: 109516-109516, ISSN: 0141-0296

The susceptibility of steel frames to global second order effects, also referred to as sway effects, ‘P–Δ’ effects and global geometric nonlinearities, is traditionally assessed through the elastic buckling load amplifier αcr. For elastic analysis, EN 1993-1-1 and other international steel design standards state that second order effects may be neglected provided αcr is greater than or equal to 10. However, when plastic analysis is employed, yielding of the material degrades the stiffness of the structure, and hence a stricter requirement of αcr ≥ 15 is prescribed in EN 1993-1-1 for second order effects to be neglected. Use of a single limit of 15 for any structural system is however considered to be overly simplistic. A more consistent and accurate approach is to determine the degree of stiffness degradation and hence the increased susceptibility to second order effects on a frame-by-frame basis. A parametric analysis to assess the stability of steel frames in the plastic regime is presented herein. A series of frames with varying geometries and load cases has been assessed. Based on the findings, a proposal for the calculation of a modified elastic buckling load factor αcr,mod, which considers the reduction in stiffness following plasticity on a frame-by-frame basis, is presented.

Journal article

Liu X, Chung K-F, Huang M, Wang G, Nethercot DAet al., 2019, Thermomechanical parametric studies on residual stresses in S355 and S690 welded H-sections, JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, Vol: 160, Pages: 387-401, ISSN: 0143-974X

Journal article

Ho HC, Chung KF, Liu X, Xiao M, Nethercot DAet al., 2019, Modelling tensile tests on high strength S690 steel materials undergoing large deformations, ENGINEERING STRUCTURES, Vol: 192, Pages: 305-322, ISSN: 0141-0296

Journal article

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

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

Walport F, Gardner L, Nethercot DA, 2019, Structural stainless steel design by advanced analysis with csm strain limits, Pages: 1107-1112

Advanced structural analysis is commonly carried out using finite element models constructed using beam elements. Beam elements are incapable of capturing the effects of local buckling. However, disregarding local buckling can lead to overestimations of system strengths leading to unsafe design. In traditional design approaches, time-consuming semi-empirical design calculations are carried out on individual members. However, with improvements in computational power and advances in software, system-level advanced analysis is now viable for widespread use in design. A proposal is made herein, in which strain limits, defined by the Continuous Strength Method, are applied to simulate local buckling in beam element models, thereby controlling the extent to which spread of plasticity, moment redistribution and strain hardening can be exploited. Strains are averaged over a finite length of member to reflect the fact that local buckling requires a finite length over which to develop and to allow for local moment gradient effects. The paper includes a numerical assessment of the proposed method for design at member level, with both I-sections and hollow sections considered. Comparisons against current design methods confirm the significant benefits of the proposed approach. Application of the approach is particularly appropriate for stainless steel structures due to the high material value and the complexities presented by the nonlinear material stress-strain response for traditional design treatments.

Conference paper

Walport F, Gardner L, Nethercot DA, 2019, Structural stainless steel design by advanced analysis with CSM strain limits, 7th International Conference on Structural Engineering, Mechanics and Computation (SEMC), Publisher: CRC PRESS-BALKEMA, Pages: 1107-1112

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

Liu X, Chung K-F, Ho H-C, Xiao M, Hou Z-X, Nethercot DAet al., 2018, Mechanical behavior of high strength S690-QT steel welded sections with various heat input energy, ENGINEERING STRUCTURES, Vol: 175, Pages: 245-256, ISSN: 0141-0296

Journal article

Cheng X, Chen Y, Niu L, Nethercot DAet al., 2018, Experimental study on H-section steel beam-column sunder cyclic biaxial bending considering the effect of local buckling, ENGINEERING STRUCTURES, Vol: 174, Pages: 826-839, ISSN: 0141-0296

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

Walport F, Gardner L, Real E, Arrayago I, Nethercot DAet al., 2018, Effects of material nonlinearity on the global analysis and stability of stainless steel frames, Journal of Constructional Steel Research, ISSN: 0143-974X

In structural frames, second order effects refer to the internal forces and moments that arise as a result of deformations under load (i.e. geometrical nonlinearity). EN 1993-1-1 states that global second order effects may be neglected if the critical load factor of the frame αcris greater than or equal to 10 for an elastic analysis, or greater than or equal to 15 when a plastic global analysis is used. No specific guidance is provided in EN 1993-1-4 for the design of stainless steel frames, for which the nonlinear stress-strain behaviour of the material will result in greater deformations as the material loses its stiffness. A study of the effects of material nonlinearity on the stability of stainless steel frames is presented herein. A series of different frame geometries and loading conditions are considered. Based on the findings, proposals for the treatment of the influence of material nonlinearity on the global analysis and design of stainless steel frames are presented.

Journal article

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

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