Publications
388 results found
Elghazouli AY, Bompa DV, Xu B, et al., 2018, Performance of Rubberised Reinforced Concrete Members under Cyclic Loading, 16th European Conference on Earthquake Engineering (16ECEE)
Bompa DV, Elghazouli AY, 2018, Seismic Performance and Application of Mechanical Splices in Dissipative RC Structures
Sirumbal-Zapata LF, Málaga-Chuquitaype C, Elghazouli AY, 2018, A three-dimensional plasticity-damage constitutive model for timber under cyclic loads, Computers and Structures, Vol: 195, Pages: 47-63, ISSN: 0045-7949
The performance of timber structures is governed by the nonlinear response at their connections, where high deformation levels and stress concentrations are developed, particularly when subjected to load reversals. To date, no constitutive model for wood under cyclic load exists which is able to incorporate its most important failure modes while considering plastic deformations and cyclic stiffness and strength degradation simultaneously. This paper presents the formulation and implementation of a plasticity-damage model with these characteristics within a continuum mechanics approach. The theoretical framework of both plasticity and damage models is described, and a detailed derivation of the constitutive equations required for their computational implementation and coupling as well as the return mapping and iterative algorithms for their integration are presented. The damage evolution process is handled by two independent scalar variables for tension and compression. A general orthotropic plasticity yield surface with isotropic hardening is employed to incorporate timber plastic flow in compression. A closed-form expression for the plasticity-damage consistent tangent operator is derived. It is demonstrated that the proposed constitutive model captures all the key characteristics required for an accurate modelling of timber under large deformation levels until failure.
Tsitos A, Bravo-Haro MA, Elghazouli AY, 2018, Influence of deterioration modelling on the seismic response of steel moment frames designed to Eurocode 8, Earthquake Engineering and Structural Dynamics, Vol: 47, Pages: 356-376, ISSN: 0098-8847
This paper assesses the influence of cyclic and in-cycle degradation on seismic drift demands in moment-resisting steel frames (MRF) designed to Eurocode 8. The structural characteristics, ground motion frequency content, and level of inelasticity are the primary parameters considered. A set of single-degree-of-freedom (SDOF) systems, subjected to varying levels of inelastic demands, is initially investigated followed by an extensive study on multi-storey frames. The latter comprises a large number of incremental dynamic analyses (IDA) on 12 frames modelled with or without consideration of degradation effects. A suite of 56 far-field ground motion records, appropriately scaled to simulate 4 levels of inelastic demand, is employed for the IDA. Characteristic results from a detailed parametric investigation show that maximum response in terms of global and inter-storey drifts is notably affected by degradation phenomena, in addition to the earthquake frequency content and the scaled inelastic demands. Consistently, both SDOF and frame systems with fundamental periods shorter than the mean period of ground motion can experience higher lateral strength demands and seismic drifts than those of non-degrading counterparts in the same period range. Also, degrading multi-storey frames can exhibit distinctly different plastic mechanisms with concentration of drifts at lower levels. Importantly, degrading systems might reach a "near-collapse" limit state at ductility demand levels comparable to or lower than the assumed design behaviour factor, a result with direct consequences on optimised design situations where over-strength would be minimal. Finally, the implications of the findings with respect to design-level limit states are discussed.
Bompa DV, Elghazouli AY, 2018, Punching Shear Strength of RC Flat Slabs Provided with Shear-Heads at Interior Connections to Steel Columns, Fib Symposium on High Tech Concrete - Where Technology and Engineering Meet, Publisher: SPRINGER INTERNATIONAL PUBLISHING AG, Pages: 823-831
Goggins J, Broderick BM, Elghazouli AY, et al., 2017, Shake Table Testing of Concentrically Braced Steel Structures With RealisticConnection Details Subjected to Earthquakes, Structures, Vol: 13, Pages: 102-118, ISSN: 0969-2126
This paper describes an experimental investigation into the seismic response of concentrically braced steel frames (CBFs). Twelve shake table tests were performed on full-scale single storey frames, each containing a pair of identical brace members. The experimental programme examined the behaviour of brace members with four different square and rectangular hollow cross-sections and a range of gusset plate connection details. The aim of the experimental study was to determine the influence of brace and gusset plate properties on CBF response from serviceability to ultimate limit states, including collapse. Consequently, all test frames were subjected to three levels of seismic excitation: (i) low-level excitation to examine elastic frame response, (ii) medium-level excitation to examine brace buckling and yielding effects, and (iii) high-level excitation to induce brace fracture. A detailed set of data on the seismic response of CBFs with realistic brace members and connections were obtained from the tests. The experiments were conducted under representative dynamic response conditions as opposed to the conventional idealised quasi-static loading procedures employed in previous experimental investigations of CBF behaviour. The results faithfully capture the behaviour of brace-gusset plate test specimens with different non-dimensional brace slenderness, brace cross-section slenderness, connection types and gusset plate detailing. The response variables measured in each test included the shaking table and frame accelerations and displacements, brace elongation and axial force, and brace member and gusset plate strains. The experimental observations include elastic frame vibration properties, acceleration and drift demands, ultimate failure modes and ductility capacity. The brace-gusset plate test specimens remained elastic at low-level excitations, brace buckling and yielding occurred in all medium-level excitation tests, while specimens exhibited brace fracture under
Xu B, Bompa DV, Elghazouli AY, et al., 2017, Behaviour of rubberised concrete members in asymmetric shear tests, Construction and Building Materials, Vol: 159, Pages: 361-375, ISSN: 0950-0618
This paper deals with the experimental behaviour of rubberised concrete members subjected to asymmetric four-point shear loading. A detailed account of tests on 15 prismatic members using conventional concrete as well as rubberised concrete, with relatively high replacement ratios of both fine and coarse mineral aggregates with rubber particles, is given. The results enable direct assessment of strength and complete deformation characteristics including the post-peak response for ultimate behaviour governed both by shear and mixed-mode tensile-shear. After describing the material properties, mix designs and member details, the main observations from detailed measurements of the crack kinematics through a digital image correlation monitoring system, with focus on members developing shear-governed response, are reported. Complementary numerical studies are undertaken using nonlinear finite element procedures which are validated against tests developing shear-governed failures. In order to provide further insight into the key response characteristics, particularly those related to ultimate strength, a number of numerical sensitivity studies employing various constitutive parameters are also carried out. Moreover, comparative assessments in terms of shear resistance, toughness and force transfer across the cracked interfaces are performed and discussed. The detailed test measurements, coupled with the results obtained from the numerical simulations, permit the definition of expressions for representing the shear resistance as a function of the rubber content and concrete compressive strength.
Bompa DV, Elghazouli AY, 2017, Ductility considerations for mechanical reinforcement couplers, Structures, Vol: 12, Pages: 115-119, ISSN: 2352-0124
Mechanical reinforcement couplers can offer considerable constructional and economic advantages in comparison with conventional methods of lap splicing, particularly when the requirements for seismic detailing exacerbates reinforcement congestion problems. However, the lack of specific codified guidance on ductility considerations hinders the application of mechanical couplers under inelastic conditions. To this end, this brief paper provides an overview of various reinforcement coupling systems, as well as a comparative assessment of their ‘in-air’ and ‘in-concrete’ performance, based on results extracted from a collated database. The main behavioural characteristics of different coupler forms are discussed, and their key performance parameters are compared. In addition to strength and ductility, the influence of the coupler size and arrangement on the ductility of structural members is discussed. The comparative assessments presented offer some guidance for the selection and application of mechanical reinforcement couplers in inelastic regions, and highlights areas in which further detailed investigations are required.
Salawdeh S, English J, Goggins J, et al., 2017, Shake table assessment of gusset plate connection behaviour in concentrically braced frames, Journal of Constructional Steel Research, Vol: 138, Pages: 432-448, ISSN: 0143-974X
Diagonal bracing members and their connections to beams and columns are the key lateral resisting components in concentrically braced frames (CBFs). Although gusset plate connections are widely used to connect bracing and frame members in such systems, their design often involves significant simplifications and idealisations due to the complexity of their behaviour under seismic loading. A conventional approach, which utilises a standard linear clearance zone that permits out-of-plane brace deformation, is typically used in the design of gusset plates. This approach can result in overly large connections with cumbersome details. The desire to achieve an improved balance between the gusset over-strength, on the one hand, and a favourable overall frame performance coupled with practical connection detailing, on the other, has prompted proposals for an improved design approach. However, before new recommendations on the design of gusset plate connections can be provided for use in codified guidance, there is a need to assess the performance of such detailing alternatives under realistic earthquake loading conditions. Accordingly, in this study, the performance of different brace connection configurations and gusset plate designs are examined using shake table testing. The paper describes twelve single-storey full scale shake table tests, which were performed on the AZALEE seismic testing facility at CEA Saclay. In seven of these tests, the gusset plates at the end of the brace members were connected to both beam and column flanges, while in the other five tests these were connected to the beam flange only. Conventional gusset plate design with a standard linear clearance was used for six tests, whereas a more balanced design with a nonlinear elliptical clearance detail was used for the others. The experimental set-up, specimen details, and loading procedures are presented, together with a detailed account of the results and observations. The main findings and their imp
Moharram MI, Bompa DV, Elghazouli AY, 2017, Performance and Design of Shear Keys in Hybrid RC Beam and Steel Column Systems, Eurosteel2017
Cedron F, Elghazouli AY, 2017, Seismic Behaviour of Single Layer Cylindrical Lattice Steel Shells, Eurosteel2017
Bompa DV, Elghazouli AY, 2017, Ultimate Behaviour and Design of Hybrid Flat Slabs with Steel Shear Heads, Eurosteel2017
Bravo-Haro M, Tsitos A, Elghazouli AY, 2017, Influence of Deterioration Modelling on Local Deformation Demands in Steel Moment Frames, Eurosteel2017
Bompa DV, Elghazouli AY, 2017, Bond-slip response of deformed bars in rubberised concrete, Construction and Building Materials, Vol: 154, Pages: 884-898, ISSN: 0950-0618
This paper is concerned with examining the complete bond-slip behaviour between deformed reinforcement bars and concrete incorporating rubber particles from recycled tyres as a partial replacement for mineral aggregates. An experimental study consisting of fifty-four pull-out tests on cylindrical rubberised and normal concrete specimens, in conjunction with two reinforcement sizes with short embedment lengths, is described. In addition to a detailed assessment of the full bond-slip relationship, the test results offer a direct interpretation of bond behaviour under practical levels of confinement and its influence on the failure modes. Particular emphasis is given to the characteristic bond behaviour of rubberised concrete in terms of maximum bond strength and splitting strength as well bond stiffness and slip parameters. The detailed test measurements and observations provided in this study enable the definition of key bond parameters depicting the interfacial behaviour between rubberised concrete and deformed bars. The findings also permit the development of modified approaches for reliable representation of the failure modes and bond capacities for the concrete materials considered in this investigation.
Moharram MI, Bompa DV, Elghazouli AY, 2017, Inelastic Assessment of Hybrid Reinforced Concrete Assemblages, fib Symposium 2017, Pages: 1336-1343
Elghazouli AY, Bompa DV, Xu B, et al., 2017, Inelastic behaviour of RC members incorporating high deformability concrete, fib Symposium 2017
Pérez Caldentey A, Mestre García C, Koutas L, et al., 2017, Innovative Reuse of all Tyre Components in Concrete: Innovative Reuse of all Tyre Components in Concrete, Publisher: University of Sheffield
Elghazouli AY, 2017, Seismic design of building structures to Eurocode 8, CSCEHKB Conference, Pages: 62-69
Elghazouli AY, 2017, Seismic Performance of Structural Members Incorporating Recycled Rubber Materials, XVII ANIDIS Conference on Earthquake Engineering, Pages: KL25-KL33
Bompa DV, Elghazouli AY, Xu B, et al., 2017, Experimental assessment and constitutive modelling of rubberised concrete materials, Construction and Building Materials, Vol: 137, Pages: 246-260, ISSN: 0950-0618
This paper focuses on examining the uniaxial behaviour of concrete materials incorporating rubber particles, obtained from recycled end-of-life tyres, as a replacement for mineral aggregates. A detailed account of a set of material tests on rubberised concrete cylindrical samples, in which fine and coarse mineral aggregates are replaced in equal volumes by rubber particles with various sizes, is presented. The experimental results carried out in this investigation, combined with detailed examination of data available from previous tests on rubberised concrete materials, show that the rubber particles influence the mechanical properties as a function of the quantity and type of the mineral aggregates replaced. Experimental evaluation of the complete stress-strain response depicts reductions in compressive strength, elastic modulus, and crushing strain, with the change in rubber content. Enhancement is also observed in the energy released during crushing as well as in the lateral strain at crushing, primarily due to the intrinsic deformability of the interfacial clamping of rubber particles which leads to higher lateral dilation of the material. The test results and observations enable the definition of a series of expressions to estimate the mechanical properties of rubberised concrete materials. An analytical model is also proposed for the detailed assessment of the complete stress-strain response as a function of the volumetric rubber ratio. Validations performed against the material tests carried out in this study, as well as those from previous investigations on rubberised concrete materials, show that the proposed models offer reliable predictions of the mechanical properties including the full axial and lateral stress-strain response of concrete materials incorporating rubber particles.
Bompa DV, Elghazouli AY, 2017, Numerical modelling and parametric assessment of hybrid flat slabs with steel shear heads, Engineering Structures, Vol: 142, Pages: 67-83, ISSN: 1873-7323
This investigation examines the performance of hybrid reinforced concrete flat slabs, incorporating fully-integrated shear-heads at connections to steel columns, through a series of numerical evaluations and parametric studies. Validations of the adopted nonlinear finite element procedures, which employ concrete damage plasticity constitutive models, are carried out against experimental results on hybrid members. Complementary verifications on conventional reinforced concrete flat slabs are also undertaken to ensure the reliability of the selected ranges for key modelling parameters. Comparison of the numerical simulations against the test results shows close correlations in terms of ultimate strength, deformations and stress levels in the constituent elements of hybrid members. This is followed by a series of parametric assessments on key structural parameters for hybrid flat slabs with steel shear heads. The results of these investigations enable the identification of three modes of failure as a function of the interaction between the shear-head and surrounding concrete. The findings permit the development of improved analytical models for predicting the response as well as the ultimate strength of such members. In addition, recommendations are given for the determination of shear-head dependent parameters, which are required for practical design purposes, with a particular focus on the embedment length and section size of the shear-head elements. The suggested expressions for assessing the shear-head characteristics offer a more reliable design approach in comparison with existing methods and are suitable for effective practical application and implementation in codified procedures.
Moharram MI, Bompa DV, Elghazouli AY, 2017, Experimental and numerical assessment of mixed RC beam and steel column systems, Journal of Constructional Steel Research, Vol: 131, Pages: 51-67, ISSN: 0143-974X
This study describes experimental and numerical investigations into the inelastic behaviour of structural assemblages consisting of reinforced concrete (RC) beams connected to steel columns by means of fully embedded shear-keys. A detailed account of the experimental results and observations from a series of fourteen full-scale hybrid steel/RC specimens is presented. In order to provide further insights into the key response characteristics, particularly those related to ultimate failure conditions, a number of numerical sensitivity assessments are also carried out. The numerical studies are undertaken using nonlinear finite element procedures which are validated against previous tests on RC members as well as the experimental results from the hybrid tests presented in this paper. The ability of the numerical models to provide faithful prediction of both RC and hybrid test results, in terms of stiffness, strength and failure mode, using a consistent set of material modelling parameters, provides confidence in the reliability of the simulation techniques. Possible failure conditions for mixed RC/steel members are assessed using a suggested hybrid Mode Index (MI). Based on the experimental and numerical evaluations, simplified analytical representations of the failure surfaces, corresponding to the ultimate modes of behaviour for the hybrid configurations examined in this study, are proposed and discussed.
Bompa DV, Elghazouli AY, 2017, Punching shear strength of RC flat slabs provided with shear-heads at interior connections to steel columns, fib Symposium 2017
Bompa DV, Elghazouli AY, 2017, Review on behaviour of mechanical reinforcement couplers in plastic hinge regions, Publisher: Imperial College London
Karagiannis V, Malaga Chuquitaype C, Elghazouli AY, 2017, Behaviour of hybrid timber beam-to-tubular steel column moment connections, Engineering Structures, Vol: 131, Pages: 243-263, ISSN: 0141-0296
This paper presents an experimental and numerical study into the response of bolted connections between Glulam timber beams and tubular steel columns. Six specimens involving two different connection types subjected to monotonically increasing bending action are examined. The first connection type incorporates top and seat angles blind-bolted to the column and jointed to the beam through long bolts. The second connection type is formed by a steel T-stub slotted into the timber beam and connected to it by means of transverse bolts. In addition, two reinforcing techniques aimed at enhancing the response of the slotted-in T-stub configuration are investigated. These include the provision of a bottom wedge angle between the beam and the column as well as the use of perpendicular-to-grain screws to delay wood splitting. The experimental set-up, connection configurations and material properties are introduced followed by a detailed account of the test results and observations. The main behavioural patterns are identified from the experiments and key response characteristics such as stiffness, capacity and failure mechanism are discussed. This paper shows that the use of bottom wedge angles leads to significant enhancement in the flexural yield strength of the T-stub connections, accompanied by a relatively small change in the location of the bolt-group point of rotation (monitored herein by means of Digital Image Correlation techniques). Besides, the use of reinforcing screws is shown to be an effective detail for substantially increasing the rotational ductility of the connections. Finite element simulations of the tests are also presented, together with a detailed description of the modelling approaches employed, in order to gain further insight into the behaviour of the connections. Finally, the applicability of simplified component-based expressions, which are suitable for practical design assessment procedures, for the estimation of the stiffness and capacity of the
Sirumbal Zapata LF, Malaga Chuquitaype C, Elghazouli AY, 2017, Coupled plasticity-damage material constitutive model for timber subjected to cyclic loading, 16th World Conference on Earthquake Engineering, Pages: Paper No 1122-Paper No 1122
Elghazouli AY, Castro JM, 2017, Design of Composite Steel/Concrete Structures, Seismic Design of Buildings to Eurocode 8, Editors: Elghazouli, Pages: 193-212, ISBN: 978-1-4987-5159-9
Elghazouli AY, Castro JM, 2017, Design of Steel Structures, Seismic Design of Buildings to Eurocode 8, Editors: Elghazouli, Pages: 157-192, ISBN: 9781498751599
Malaga Chuquitaype C, Elghazouli AY, 2017, Design of Timber Structures, Seismic Design Of Buildings To Eurocode 8, Editors: Elghazouli, Pages: 213-234
Moharram M, Bompa D, Elghazouli A, 2017, Inelastic assessment of hybrid RC beams to steel column configurations using structural steel shear-keys, Pages: 1336-1343
This study describes experimental and numerical investigations into the inelastic behaviour of hybrid reinforced concrete (RC) beams. The RC beams are connected to steel columns by means of fully embedded structural steel profiles. Observations from a series of ten full-scale hybrid Steel/RC specimens are presented. Nonlinear finite element procedures are carried out and validated against the experimental results from the hybrid tests in this paper. The ability of the numerical models to provide faithful prediction, using a consistent set of material modelling parameters, provides a high level of confidence in the reliability of the simulation techniques. Finally, some simplified analytical representations of the failure surfaces are proposed in which potential failure conditions are predicted and classified in reference to a suggested hybrid Mode Index.
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