Publications
388 results found
Elghazouli AY, 2017, Seismic Design of Buildings to Eurocode 8 - Second Edition, London and New York, Publisher: Spon Press - Taylor & Francis, ISBN: 9780415447621
Tsitos A, Elghazouli AY, 2016, Evaluation of loading protocols for assessing local seismic demands in steel buildings designed to EC8, 16th World Conference on Earthquake Engineering, Pages: Paper No 1559-Paper No 1559
Bravo-Haro MA, Tsitos A, Elghazouli AY, 2016, Influence of cyclic degradation on inelastic seismic demands in steel moment frames, 16th World Conference on Earthquake Engineering, Pages: paper No 1033-paper No 1033
Bompa DV, Elghazouli AY, 2016, Failure Assessment of Combined Hybrid Flat Slab and Steel Column Systems, PSSC'16, 11th Pacific Structural Steel Conference, Pages: 841-848
Tsitos A, Elghazouli AY, 2016, Seismic Performance of Steel Frames Considering Alternative Connection Configurations, PSSC'16, Pacific Structural Steel Conference, Pages: 584-591
Elghazouli AY, 2016, Seismic Performance and Design of Concentrically Braced Steel Frames, PSSC'16, 11th Pacific Structural Steel Conference, Pages: 68-75
Bompa DV, Elghazouli AY, 2016, Innovative Reuse of all Tyre Components in Concrete: Technical report on medium and large scale tests, Publisher: Imperial College London
Bompa DV, Elghazouli AY, 2016, Structural performance of RC flat slabs connected to steel columns with shear heads, Engineering Structures, Vol: 117, Pages: 161-183, ISSN: 1873-7323
This paper investigates the structural performance of hybrid members consisting of reinforced concrete flat slabs, with and without shear reinforcement, connected to steel columns by means of fully integrated shear-heads. A detailed account of the results from a series of six large scale tests on this form of hybrid structural system is provided. The test results offer a direct evaluation of the full load-deformation behaviour of the specimens as well as the ultimate punching shear strength attained prior to failure at the critical slab perimeter outside the shear-head region. The experimental findings enable the development of analytical models that depict the rotational response and flexural strength as a function of the shear-head embedment length, layout and section size. Additionally, the test results support the definition of a shear-head dependent control perimeter which is used in conjunction with the analytical slab models for full assessment of punching shear strength. The adequacy of strength predictions incorporated in current design methods for conventional reinforced concrete members are also examined in the paper. It is shown that existing design procedures either lack direct guidance for members provided with shear-heads, or lead to overly conservative strength predictions. Finally, in order to provide a reliable evaluation of the ultimate punching shear strength of hybrid elements, analytical design expressions which account for the characteristics of the shear-head system, are proposed. In comparison with conventional reinforced concrete design provisions, the suggested approach captures in a more realistic manner the influence of the embedded length of the shear-heads for such hybrid members with or without shear reinforcement.
Stylianidis PM, Nethercot DA, Izzuddin BA, et al., 2016, Robustness assessment of frame structures using simplified beam and grillage models, Engineering Structures, Vol: 115, Pages: 78-95, ISSN: 1873-7323
Simplified analysis methods derived in previous studies are employed for studying the progressive collapse behaviour of steel and composite buildings. A regular frame building is considered and various scenarios of sudden column removal, each affecting different floor areas in terms of geometry and boundary conditions, are applied. Descriptions of the pseudo-static responses of the various constitutive beams are obtained based on both detailed representations of the nonlinear static responses and by applying a new simplified approach proposed in a separate publication. Comparisons between the results of the two methods confirm that the simplified approach is capable of describing behaviour with reasonable accuracy. By employing a simplified multi-level assessment approach that has been previously derived at Imperial College, grillage-type approximations are obtained and used to examine the floor dynamic behaviour for the various column removal cases. It is found that, although the structural response varies depending on the location of the initial damage, substantial connection strength is required in all cases in order to provide resistance to progressive collapse. In addition, for average levels of connection ductility, failure most likely occurs prior to the development of tensile catenary action in the beams, which indicates that the provision of tying resistance may not be effective in enhancing robustness. Therefore, the combined action of flexure and compressive arching in the beams is likely to form the principal collapse resisting mechanism in common practical applications, which confirms similar conclusions made in previous studies at Imperial. The provision of adequate levels of connection moment capacity – in combination with sufficient ductility supply – is, therefore, the most effective way of securing structural robustness.
Stylianidis PM, Nethercot DA, Izzuddin BA, et al., 2016, Study of the mechanics of progressive collapse with simplified beam models, Engineering Structures, Vol: 117, Pages: 287-304, ISSN: 1873-7323
Methods for assessing structural robustness need to move away from the traditional norms of prescriptive rules and become more similar to those used in conventional structural design. They should therefore be based on a sound understanding of the mechanics of the problem and provide quantitative indication of its effects. Several Codes and Design Guides consider the sudden column removal approach as their principal method for progressive collapse assessment. The level of robustness is defined based on the capability of the remaining structure for sustaining the additional loading imposed by the column loss. Most likely, the beams adjacent to the lost column and their supporting connections form the principal load paths. The present paper presents a detailed study of the response of those components under the conditions experienced following column removal. Suitable analysis approaches that have been previously developed at Imperial College London are employed to investigate the basic features of the behaviour, while several simplifications are applied for exploring particular effects. The study concludes with the development of a simplified method for simulating the nonlinear dynamic response of axially restrained and unrestrained beams following column removal. The capability of the new simplified method to accurately describe performance is demonstrated through a set of suitable applications presented in a separate publication.
Bompa DV, Elghazouli AY, 2016, Connections of reinforced concrete beams or slabs to steel columns: Design examples, Publisher: Imperial College London
Chen A, Louca LA, Elghazouli AY, 2016, Behaviour of cylindrical steel drums under blast loading conditions, INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, Vol: 88, Pages: 39-53, ISSN: 0734-743X
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- Citations: 12
Málaga-Chuquitaype C, Elghazouli AY, 2016, Design of timber structures, Seismic Design of Buildings to Eurocode 8, Second Edition, Pages: 213-234, ISBN: 9781498751605
Well-designed and well-constructed timber structures can have an excellent response under earthquake loading due primarily to the high strength to weight ratio of wood. Nevertheless, the seismic performance of timber buildings involves various inter-related factors that need to be properly understood. Many of the aspects related to the resistance of timber buildings spring from the atypical mechanical characteristics of wood as a construction material. In particular, there are significant differences in wood strength and stiffness depending on the orientation of the load with respect to the grain direction as depicted in Figure 8.1. It follows from the schematic strain-stress curves, indicated in Figure 8.1, that tension failures in wood are brittle and should be avoided while compressive behaviour (parallel to the grain) is a preferred mode of failure but should be limited. In fact, it is a typical approach of codes of practice to ensure a ductile failure mechanism by inducing yielding in metallic connectors between timber members instead of the wood material itself in order to provide a sustained source of energy dissipation during seismic shaking.
Elghazouli AY, Castro JM, 2016, Design of steel structures, Seismic Design of Buildings to Eurocode 8, Second Edition, Pages: 157-192, ISBN: 9781498751605
In line with current seismic design practice, steel structures may be designed to EC8 according to either non-dissipative or dissipative behaviour. The former, through which the structure is dimensioned to respond largely in the elastic range, is normally limited to areas of low seismicity or to structures of special use and importance; it may also be feasible if vibration reduction devices are incorporated. Otherwise, codes aim to achieve economical design by employing dissipative behaviour in which considerable inelastic deformations can be accommodated under significant seismic events. In the case of irregular or complex structures, detailed non-linear dynamic analysis may be necessary. However, dissipative design of regular structures is usually performed by assigning a structural behaviour factor (i.e. force reduction or modification factor), which is used to reduce the code-specified forces, resulting from idealised elastic response spectra. This is carried out in conjunction with the capacity design concept, which requires an appropriate determination of the capacity of the structure based on a pre-defined plastic mechanism, often referred to as failure mode, coupled with the provision of sufficient ductility in plastic zones and adequate over-strength factors for other regions.
Elghazouli AY, Castro JM, 2016, Design of composite steel/concrete structures, Seismic Design of Buildings to Eurocode 8, Second Edition, Pages: 193-212, ISBN: 9781498751605
The design of composite steel/concrete buildings in EC8, covered in Section 7 of EN1998-1 (2004), largely follows the general methodology adopted for steel structures (Section 6 of EN1998-1). Accordingly, most of the approaches and procedures discussed in the previous chapter also apply to composite steel/concrete structures, with some differences related mainly to ductility requirements and capacity design considerations. This chapter highlights these differences, discusses a number of key behavioural and design aspects, and concludes with an illustrative design example.
Bompa DV, Elghazouli AY, 2015, Connections of reinforced concrete beams or slabs to steel columns. Calibration of reference design methods, Publisher: Imperial College London
Bompa DV, Elghazouli AY, 2015, Connections of reinforced concrete beams or slabs to steel columns: Experiments, Publisher: Imperial College London
Karagiannis V, Malaga Chuquitaype C, Elghazouli AY, 2015, Modified foundation modelling of dowel embedment in glulam connections, Construction and Building Materials, Vol: 102, Pages: 1168-1179, ISSN: 0950-0618
This paper examines the embedment behaviour of single-dowel connections in Scandinavian Spruce Glulam by means of experimental and numerical investigations. First, the experimental results of a series of single-dowel tests on samples of different geometry and grain directions are presented. The evolution of local strain concentrations around the fastener at increasing levels of bearing deformation, is reported in detail by means of non-contact field strain measurements and its implications are discussed. Detailed Finite Element simulations are also carried out and subsequently employed to highlight the main features of the response of doweled connections in glulam. A foundation model, initially developed for Douglas-fir (Pseudotsuga menziesii) timber, is upgraded and adapted for Scandinavian Spruce Glulam (Picea abies) elements subjected to loads acting perpendicular and parallel to the grain direction. The proposed model is based on the definition of equivalent material parameters for the crushing region around the dowel hole. To this end, relationships for the estimation of material characteristics as a function of the crushing volume are suggested. The validity and accuracy of the proposed modified foundation models are examined against the experimental results. It is shown the improved foundation model is able to simulate the embedment stiffness, capacity and inelastic behaviour of single-dowel connections on glulam with reasonable accuracy for strains of up to 8%, and can therefore be used for design and assessment purposes.
Bompa DV, Elghazouli AY, 2015, Ultimate shear behaviour of hybrid reinforced concrete beam-to-steel column assemblages, Engineering Structures, Vol: 101, Pages: 318-336, ISSN: 1873-7323
This paper examines the shear transfer mechanisms and ultimate behaviour of hybrid systems consisting of reinforced concrete beams connected to structural steel columns. A series of five large scale tests on structural assemblages, in which steel shear-arms are welded directly to the steel columns and embedded in the reinforced concrete beams, is presented. After describing the experimental arrangement and specimen details, the main results and observations obtained from the tests are provided and discussed. The test results offer a direct evaluation of the ultimate shear behaviour of such hybrid systems. The experimental findings also enable a comparison with the strength predictions obtained from analytical models which are commonly used in the design of conventional reinforced concrete members. The discussions and comparative assessments presented in this paper provide an insight into the influence of various shear transfer mechanisms including transverse reinforcement, compressive zones, residual tensile stresses, aggregate interlock, and dowel action, in addition to the interfacial bond between the steel profile and concrete. The activation and contribution of the key shear transfer mechanisms are assessed in light of the experimentally-monitored crack growth, path and pattern, as well as in comparison with widely-adopted analytical approaches. The results show that the contribution of each transfer mechanism is a function of the crack kinematics and corresponding level of applied load. Finally, modifications to existing analytical approaches for conventional reinforced concrete elements are proposed in order to provide a reliable evaluation of the ultimate shear capacity of such hybrid systems. The suggested expressions account for the influence of the shear-arms' characteristics on the ultimate shear strength, and offer a more realistic prediction of the behaviour in comparison with conventional reinforced concrete design provisions.
Stylianidis PM, Nethercot DA, Izzuddin BA, et al., 2015, Modelling of beam response for progressive collapse analysis, Structures, Vol: 3, Pages: 137-152, ISSN: 2352-0124
A fundamental aspect of the progressive collapse behaviour of building structures is the response of axially restrained beams following partial or total loss of the load bearing capacity of a supporting member. Owing to the various complex effects involved such as material and geometric nonlinearity, advanced numerical approaches tend to be the most effective tools for modelling performance. Such approaches, however, lack the simplicity needed for common use and may provide only limited capability for understanding structural behaviour. For such purposes, more limited analysis approaches that can address adequately the basic features of performance are likely to be more productive. One such method for modelling the response of axially restrained steel and composite beams following column loss is presented in this paper. The method involves explicit modelling of the connection behaviour and employs conventional structural analysis principles to describe beam performance using accessible spreadsheet calculations. Following careful verification against detailed numerical analyses and validation against available experimental results, the proposed method is deemed capable of modelling the various complex features of response with excellent accuracy. Therefore, it may form a promising advance in studying and understanding the basic mechanics of the problem.
Nip KH, Gardner L, Elghazouli AY, 2015, Ultimate behaviour of steel braces under cyclic loading, Proceedings of the ICE - Structures and Buildings, Vol: 166, Pages: 219-234, ISSN: 0965-0911
Under significant seismic loading conditions, the response of concentrically braced frames largely depends on the behaviour of the diagonal braces, which represent the key energy dissipating zones. Although the hysteretic response of steel braces under cyclic axial loading has been examined in previous studies, there is a need for further assessments that focus on quantifying failure. This paper describes the development of detailed finite-element models of hollow sections subjected to cyclic axial loading. The effects of initial imperfections and cyclic hardening are taken into consideration and the models are validated against data from 19 tests. A method to predict the fracture life of bracing members under cyclic loading is also described. Using the numerical models, parametric studies are undertaken to assess the influence of global and local slendernesses on the performance of the braces – both are found to affect the occurrence and severity of local buckling under cyclic loading, which causes high localised strains at the corner areas of sections, leading to fatigue fracture. A predictive equation addressing the coexisting influence of global slenderness and local slenderness on displacement ductility is presented. The observations in the current study are compared with conclusions from other experimental programmes, and the discrepancy between the findings is discussed.
Stylianidis PM, Nethercot DA, Izzuddin BA, et al., 2015, Modelling of beam response for progressive collapse analysis, Structures, Vol: 3, Pages: 137-152, ISSN: 2352-0124
A fundamental aspect of the progressive collapse behaviour of building structures is the response of axially restrained beams following partial or total loss of the load bearing capacity of a supporting member. Owing to the various complex effects involved such as material and geometric nonlinearity, advanced numerical approaches tend to be the most effective tools for modelling performance. Such approaches, however, lack the simplicity needed for common use and may provide only limited capability for understanding structural behaviour. For such purposes, more limited analysis approaches that can address adequately the basic features of performance are likely to be more productive. One such method for modelling the response of axially restrained steel and composite beams following column loss is presented in this paper. The method involves explicit modelling of the connection behaviour and employs conventional structural analysis principles to describe beam performance using accessible spreadsheet calculations. Following careful verification against detailed numerical analyses and validation against available experimental results, the proposed method is deemed capable of modelling the various complex features of response with excellent accuracy. Therefore, it may form a promising advance in studying and understanding the basic mechanics of the problem.
Chen A, Elghazouli AY, Louca LA, 2015, Blast assessment of industrial steel structures, CONFAB 2015 - Int Conference on Structural Safety under fire and Blast, Pages: 500-509
Chen A, Louca LA, Elghazouli AY, 2015, Blast assessment of steel switch boxes under detonation loading scenarios, INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, Vol: 78, Pages: 51-63, ISSN: 0734-743X
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- Citations: 8
Malaga-Chuquitaype C, Elghazouli AY, Liu C, 2015, Response of blind-bolted connections under extreme dynamic actions, Eurosteel 2014, 7th International Conference on Steel and Composite Structures
Bompa DV, Elghazouli AY, 2015, Connections of RC beam/slab to steel columns by means of shearkeys: Design of hybrid joints by means of strut-and-tie method, Publisher: Imperial College London
Broderick BM, Goggins J, Beg D, et al., 2015, Assessment of the seismic response of concentrically-braced steel frames, Geotechnical, Geological and Earthquake Engineering, Vol: 35, Pages: 327-344, ISSN: 1573-6059
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- Citations: 10
Elghazouli AY, 2015, Seismic Code Developments for Steel and Composite Structures, PERSPECTIVES ON EUROPEAN EARTHQUAKE ENGINEERING AND SEISMOLOGY, VOL 2, Vol: 39, Pages: 129-151
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- Citations: 1
Malaga Chuquitaype C, Elghazouli AY, Enache R, 2014, Contribution of secondary frames to the mitigation of collapse in steel buildings subjected to extreme loads, Structure and Infrastructure Engineering, Pages: 1-16, ISSN: 1744-8980
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