Publications
578 results found
Tan QH, Gardner L, Han LH, et al., 2018, Analysis of concrete-filled stainless steel tubular columns under combined fire and loading, 12th International Conference on Advances in Steel-Concrete Composite Structures (ASCCS), Publisher: UNIV POLITECNICA VALENCIA, Pages: 825-833
Wang F, Young B, Gardner L, 2018, Numerical study of concrete-filled austenitic stainless steel CHS stub columns with high-strength steel inner tubes, 12th International Conference on Advances in Steel-Concrete Composite Structures (ASCCS), Publisher: UNIV POLITECNICA VALENCIA, Pages: 343-350
Laim L, Rodrigues JPC, Gardner L, 2018, Numerical parametric study of cold-formed steel C-shaped columns in fire, 10th International Conference on Structures in Fire, Pages: 695-702
Tan Q, Gardner L, Chen B, et al., 2018, Fire behaviour of steel reinforced concrete filled stainless steel tubular (SRCFSST) columns with square hollow sections, 10th International Conference on Structures in Fire, Pages: 513-520
Meng X, Gardner L, 2018, Testing and numerical modelling of cold-formed high strength steel circular hollow sections, First Workshop of the High Performance Steel Structures Research Council (HPSSRC)
Walport F, Gardner L, Real E, et 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.
McCann F, Gardner L, Silvestre N, 2018, Postbuckling strength of slender elliptical hollow sections in bending, Eighth International Conference on Thin-Walled Structures, ICTWS 2018
Wang F, Young B, Gardner L, 2018, Behaviour of concrete-filled double skin tubular stub columns with stainless steel outer tubes, Eighth International Conference on Thin-Walled Structures, ICTWS 2018
Meng X, Gardner L, 2018, Cross-sectional behaviour of cold-formed high strength steel CHS under combined axial compression and bending, Eighth International Conference on Thin-Walled Structures, ICTWS 2018
Kucukler M, Gardner L, 2018, A stiffness reduction method for lateral-torsional buckling assessment of web-tapered steel beams, Eighth International Conference on Thin-Walled Structures, ICTWS 2018
Fieber A, Gardner L, Macorini L, 2018, Design of steel structures using advanced analysis with strain limits, Eighth International Conference on Thin-Walled Structures, ICTWS 2018
Yun X, Gardner L, 2018, Stress-strain curves for cold-formed steels, Eighth International Conference on Thin-Walled Structures, ICTWS 2018
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
Walport F, Gardner L, Nethercot D, 2018, Stability of steel frames in the plastic regime, Eighth International Conference on Thin-Walled Structures, ICTWS 2018
Gardner L, 2018, Stability and design of stainless steel structures – review and outlook, Eighth International Conference on Thin-Walled Structures, ICTWS 2018 (Keynote)
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
Buchanan C, Gardner L, Zhao O, et al., 2018, Design of stainless steel CHS beam-columns, Pages: 503-511
The EN 1993-1-4 (2015) design approach for stainless steel CHS beam-column members has been observed from prior experimental studies to provide capacity predictions that can be either overly conservative or unconservative depending upon the ratio of axial load to bending moment. Hence, a numerical parametric study has been undertaken to explore the buckling response of stainless steel CHS beam-columns, covering austenitic, duplex and ferritic grades with a wide range of local and global slendernesses and applied loading eccentricities. Over 2000 numerical results have been generated and used to assess new design proposals for stainless steel beam-columns, featuring improved compression and bending end points and new interaction factors. The new proposals are more consistent and, on average, 4% more accurate in their resistance predictions than the current EN 1993-1-4 (2015) design approach. The reliability of the existing and new proposals has been verified by means of statistical analyses according to EN 1990 (2005).
Ajamyan AN, Nassirnia M, Heidarpour A, et al., 2018, Direct strength prediction of innovative corrugated columns, Pages: 467-474
This paper responds to the need for a theoretical model to describe the structural strength capacity of innovative hollow corrugated columns consisting of four cold-formed corrugated mild steel plates. Interest in these columns has been growing over a number of years, due to high ratio of axial load bearing capacity to weight. The paper utilises the Direct Strength Method (DSM) to calculate the axial strength of aforementioned columns while the results are compared with those obtained from experiments and finite element models. Existing formulations are extended to predict local failure of these columns over a vast range of slenderness with a good degree of accuracy. The results show the appropriateness of this method as an alternative for analytical capacity prediction of innovative corrugated columns.
Wang F, Young B, Gardner L, 2018, Structural performance of concrete-filled double skin tubular beams with eccentric inner tubes, Pages: 117-123
Concrete-Filled Double Skin Tubular (CFDST) beams with stainless steel as the outer tube, carbon steel as the inner tube and sandwiched concrete infill between the tubes are presented. Previous studies on CFDST beams have revealed significant enhancements in flexural capacity due to the interaction between concrete and metal tubes. In this study, an innovative form of CFDST beam has been proposed, whereby the inner tube is positioned in the tensile zone of the sections. Hence, the beam sections can resist higher bending moment compared to those sections with the inner tube located at the centroid. A series of tests was performed on CFDST beams with an eccentric inner tube. Nine three-point major-axis bending tests were conducted. The full moment–deflection histories, moment capacities and failure modes of the CFDST beams are presented herein. The experimental results were used to evaluate the bending resistances predicted by the American and European Specifications.
dos Santos GB, Gardner L, Kucukler M, 2017, A method for the numerical derivation of plastic collapse loads, Thin-Walled Structures, Vol: 124, Pages: 258-277, ISSN: 0263-8231
Two key reference loads: (i) the plastic collapse load and (ii) the elastic buckling load are commonly used to determine the slenderness and hence the resistance of structural steel elements in international design standards. Utilising numerical methods, the plastic collapse loads are typically obtained through a Materially Nonlinear Analysis (MNA) based on small displacement theory (i.e. a first order plastic analysis). However, such analyses can often yield ambiguous or even spurious results due to, for example, the load-deformation paths not reaching a peak value or reaching a peak value but only after unrealistically large deformations, resulting in misleading predictions of plastic collapse loads and mechanisms. In this paper, a standardised means of determining plastic collapse loads from numerical MNA based on attaining a tangent stiffness of 1% of the initial slope of the load-deformation curve is presented. Furthermore, for analyses that terminate prematurely, an extrapolation technique to predict the full load-deformation paths and hence estimate the plastic collapse load is proposed. The accuracy and practicality of the proposed approach over existing methods is illustrated for a wide range of structural scenarios, with an emphasis on structural elements under concentrated transverse forces.
Yun X, Gardner L, Boissonnade N, 2017, The continuous strength method for the design of hot-rolled steel cross-sections, Engineering Structures, Vol: 157, Pages: 179-191, ISSN: 0141-0296
The continuous strength method (CSM) is a deformation-based structural design approach that enables material strain hardening properties to be exploited, thus resulting in more accurate and consistent capacity predictions. To date, the CSM has featured an elastic, linear hardening material model and has been applied to cold-formed steel, stainless steel and aluminium. However, owing to the existence of a yield plateau in its stress-strain response, this model is not well suited to hot-rolled carbon steel. Thus, a tri-linear material model, which can closely represent the stress-strain response of hot-rolled carbon steel, is introduced and incorporated into the CSM design framework. Maintaining the basic design philosophy of the existing CSM, new cross-section resistance expressions are derived for a range of hot-rolled steel structural section types subjected to compression and bending. The design provisions of EN 1993-1-1 and the proposed CSM are compared with experimental results collected from the literature and numerical simulations performed in this paper. Overall, the CSM is found to offer more accurate and consistent predictions than the current design provisions of EN 1993-1-1. Finally, statistical analyses are carried out to assess the reliability level of the two different design methods according to EN 1990 (2002).
Trahair NS, Bradford MA, Nethercot DA, et al., 2017, The Behaviour and Design of Steel Structures to EC3: Fourth Edition, ISBN: 9780415418652
The fully revised fourth edition of this successful textbook fills a void which will arise when British designers start using the European steel code EC3 instead of the current steel code BS5950. The principal feature of the forth edition is the discussion of the behaviour of steel structures and the criteria used in design according to the British version of EC3. Thus it serves to bridge the gap which too often occurs when attention is concentrated on methods of analysis and the sizing of structural components. Because emphasis is placed on the development of an understanding of behaviour, many analytical details are either omitted in favour of more descriptive explanations, or are relegated to appendices. The many worked examples both illustrate the behaviour of steel structures and exemplify details of the design process. The Behaviour and Design of Steel Structures to EC3 is a key text for senior undergraduate and graduate students, and an essential reference tool for practising structural engineers in the UK and other countries.
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.
Saliba NG, Gardner L, 2017, Deformation-based design of stainless steel cross-sections in shear, Thin-Walled Structures, Vol: 123, Pages: 324-332, ISSN: 0263-8231
The continuous strength method (CSM) is a recently developed deformation-based design method for metallic structures. In this method, cross-section classification is replaced by a normalized deformation capacity, which defines the maximum strain that a cross-section can endure prior to failure. This limiting strain is used in conjunction with an elastic, linear-hardening material stress-strain model to determine cross-section capacity allowing for the influence of strain hardening. To date, the CSM has been developed for the determination of cross-section capacity under normal stresses (i.e. compression, bending and combined loading), where it has been shown to offer more accurate predictions than current codified methods. In this paper, extension of the CSM to the determination of shear resistance is described. The relationship between the normalized shear deformation capacity, referred to as the shear strain ratio, and the web slenderness is first established on the basis of experimental and numerical data. The material model and proposed resistance functions are then described. Comparisons of the developed method with the ultimate shear capacity of a series of tested stainless steel plate girders show that improved resistance predictions of test capacity over current design methods are achieved.
Kucukler M, Gardner L, 2017, Design of laterally restrained web-tapered steel structures through a stiffness reduction method, Journal of Constructional Steel Research, Vol: 141, Pages: 63-76, ISSN: 0143-974X
A stiffness reduction method for the design of laterally restrained web-tapered steel structures fabricated through the welding of individual steel plates is presented in this paper. Stiffness reduction functions for welded members, accounting fully for the deleterious influence of the spread of plasticity and imperfections on the structural resistance, are developed. The method is implemented through (i) dividing tapered members into prismatic segments along their lengths, (ii) reducing the flexural stiffness of each segment by means of the developed stiffness reduction functions considering the first-order forces and cross-section properties of each segment, (iii) performing Geometrically Nonlinear Analysis and (iv) making cross-section strength checks. Essentially, it is proposed to replace the current typical approach to structural design of conducting a simple elastic (with nominal stiffness) structural analysis followed by elaborate member checks with an integrated process utilising more sophisticated second-order analysis (with stiffness reduction) but very simple design checks. The distribution of internal forces within the structure is captured more accurately due to the allowance for imperfections, residual stresses and plasticity through stiffness reduction and the allowance for frame and member instability effects through the use of second-order analysis. The need for determining effective lengths and for conducting member buckling checks is also eliminated. Verification of the proposed approach against the results obtained from nonlinear shell finite element modelling is presented for various tapering geometries, slenderness values and loading conditions. Assessment of the proposed method against the European and North American steel design codes for tapered steel structures is also provided.
Long YL, Li WT, Dai JG, et al., 2017, Experimental study of concrete-filled CHS stub columns with inner FRP tubes, Thin-Walled Structures, Vol: 122, Pages: 606-621, ISSN: 0263-8231
An experimental study into the axial compressive behaviour of concrete-filled circular hollow section (CHS) steel columns with internal fibre reinforced polymer (FRP) tubes is presented in this paper. A total of 17 concrete-filled steel tubular (CFST) columns were tested, 15 with an inner FRP tube and 2 with no inner tube. Complementary material tests and tests on 15 FRP-confined concrete (FCC) columns were also carried out. The varied test parameters included the concrete strength, the ratio of the diameter of the steel tube to that of the FRP tube, the diameter to wall thickness ratio of the inner FRP tube and the type (influencing principally the rupture strain) of the FRP. It was found that the presence of the inner FRP tube led to considerably improved axial compressive behaviour due to the greater levels of confinement afforded to the ‘doubly-confined’ inner concrete core; the load-bearing capacity was increased by between about 10% and 50% and the ductility was also enhanced. Greater benefits arose with (1) increasing diameter of the inner FRP tube due to the increased portion of the cross-section that is doubly-confined and (2) increasing wall thickness of the inner FRP tube due to the increased level of confinement afforded to the inner concrete core. The load-deflection responses of all tested specimens were reported, revealing that failure was generally gradual with no sharp loss in load-bearing capacity, implying that the embedment of the inner FRP tube within the concrete enables it to continue to provide a reasonable degree of confinement even after the initiation of fibre rupture; this is different to the sudden loss of confinement typically observed in FRP externally jacketed concrete columns.
Lapira L, Wadee MA, Gardner L, 2017, Stability of multiple-crossarm prestressed stayed columns with additional stay systems, Structures, Vol: 12, Pages: 227-241, ISSN: 2352-0124
Prestressed stayed columns have an enhanced resistance to buckling through the effective use of crossarms and pretensioned stays when compared to conventional columns. An analytical derivation of the minimum, linear optimum and maximum initial pretension forces for configurations of prestressed stayed columns with multiple crossarms and additional stays is presented for the first time. The findings are validated through comparisons with finite element models developed in the commercial package ABAQUS. The influence of the initial pretension on the load-carrying capacity of the configurations considered is also analysed, providing insight into the actual optimum initial pretension force for the configurations accounting for the significance of geometric nonlinearities.
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.
Gkantou M, Theofanous M, Wang J, et al., 2017, Behaviour and design of high-strength steel cross-sections under combined loading, Proceedings of the Institution of Civil Engineers: Structures and Buildings., Vol: 170, Pages: 841-854, ISSN: 0965-0911
The behaviour of hot-rolled high-strength steel (HSS) tubular sections under combined compression and uniaxialbending was investigated both experimentally and numerically. The experimental programme encompassed a seriesof material coupon tests, initial geometric imperfection measurements, residual stress measurements and 12 tests onstub columns subjected to uniaxial eccentric compression. Numerical models were developed and validated againstthe experimental results. An extensive parametric study was then performed with the aim of generating furtherstructural performance data over a wider range of cross-section slendernesses, aspect ratios and applied eccentricities.The results were utilised for an assessment of the applicability of relevant Eurocode provisions to HSS cross-sectionsunder combined loading. Conclusions regarding the applicability of Eurocode interaction curves to S460 andS690 square and rectangular hollow sections are presented.
Tan Q, Gardner L, Han L-H, 2017, Performance of steel reinforced concrete filled stainless steel tubular columns at elevated temperature, 15th East Asia Pacific Conference on Structural Engineering and Construction, Pages: 522-537
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