Imperial College London

ProfessorAhmedElghazouli

Faculty of EngineeringDepartment of Civil and Environmental Engineering

Professor of Structural Engineering - Section Head
 
 
 
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Contact

 

+44 (0)20 7594 6021a.elghazouli

 
 
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Assistant

 

Ms Ruth Bello +44 (0)20 7594 6040

 
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Location

 

440Skempton BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

330 results found

Song SY, Guo YT, Fan JS, Elghazouli AYet al., 2021, Shear contribution of flange dowel action in steel–concrete–steel​ composite structures, Thin-Walled Structures, Vol: 169, ISSN: 0263-8231

The shear contribution of flange dowel action in steel–concrete–steel composite structures is studied in this paper. Tests on the shear behaviour of beam-type specimens are carried out, to complement existing experimental results, with particular focus on investigating the influence of flange thickness. Various methods for evaluating the shear resistance are discussed, and a detailed beam-on-foundation procedure is then developed considering both the elastic and plastic characteristics. The suitability of beam-scale numerical models for representing dowel behaviour is also examined, and a local-scale dowel model is constructed and employed in numerical parametric studies in order to calibrate an analytical beam-on-foundation approach. The parametric assessment includes a wide range of design variables and considers different cases of compression or tension foundations. The equivalent depth in concrete, flange yielding ratio, and supporting foundation strength ratio, are shown to be three key parameters governing the dowel stiffness and strength. Based on the theoretical and numerical findings, a simplified design method, that captures realistically the contribution of flange dowel action, is proposed and validated against a wide range of test data, including those from this study, and shown to offer highly reliable predictions.

Journal article

Bompa DV, Elghazouli AY, 2021, Mechanical properties of hydraulic lime mortars and fired clay bricks subjected to dry-wet cycles, Construction and Building Materials, Vol: 303, Pages: 1-17, ISSN: 0950-0618

This paper examines the influence of moisture and chlorides on the mechanical properties of natural hydraulic lime mortars, fired clay brick materials and masonry components. Besides assessing three types of mortars incorporating limes with different hydraulicity levels, a cement-only mortar was also investigated for comparison purposes. The test results indicate that all the hydraulic lime mortars had mass accumulation in the range of 11–14% after being subjected to wet-dry cycles in a sodium chloride solution, whilst the mass uptake was in the range of 3–8% for those made of cement. Salt accumulation produced a denser material leading to compressive cube and flexural strength enhancements by factors ranging between 1.6 and 4.7 in comparison to those in ambient-dry conditions, with even higher factors obtained for compressive cylinder strengths and elastic moduli. In contrast, lime mortar subjected to water-only wet-dry cycles showed constant mass or mass loss, due to cracking. Uniaxial compressive strengths of cylindrical brick cores were about 8.5% higher due to wet-dry cycles in chloride solution, and by about 14.9% lower due to wet-dry cycles in water, compared to the ambient-dry case. Complementary compressive tests on masonry cylinders in ambient-dry conditions were also used to assess the adequacy of existing compressive strength assessment expressions. After modifying the expressions by a set of proposed calibration factors, these are employed to undertake a sensitivity study using the mechanical properties of mortars and bricks subjected to wet-dry cycling. The results of the sensitivity study, combined with strength ranges available in the literature, lead to an identification of a suitable range of materials that can be considered for rehabilitation of some forms of historic masonry.

Journal article

Martinez-Paneda M, Elghazouli A, 2021, Optimal application of fluid viscous dampers in tall buildings incorporating integrated damping systems, The Structural Design of Tall and Special Buildings, ISSN: 1541-7808

This paper examines the detailed performance of an Integrated-Damping-System (IDS) approach which wasrecently introduced to provide large damping levels by enabling two parts of a building to move independentlythrough a parallel arrangement of springs and fluid viscous dampers. Extensive assessments into thecharacteristics and distribution of constituent dampers are illustrated through the dynamic response of a typical300m central-core building. Besides examining the system performance under typical wind conditions andselected seismic excitations, five damper placement methods are assessed for various linear and nonlinear damperexponents. It is shown that intermediate exponents provide the best overall response. However, when the designtargets a particular damping, deformation or acceleration related performance parameter, specific combinationsof damper exponent and distribution can result in an optimal application. Most importantly, due to the underlyingIDS nature, which acts as an inherent large-mass damper, the findings show that the overall performance is nothighly sensitive to the damper placement and does not necessitate the use of an advanced distribution. Whilstspecific placements can be adopted to refine targeted performance aspects where necessary, simple and practicaluniform or stiffness proportional arrangements can be consistently employed with the IDS to provide a highlyeffective solution.

Journal article

Xu B, Li H, Bompa DV, Elghazouli AY, Chen Jet al., 2021, Performance of polymer cementitious coatings for high-voltage electrical infrastructure, Infrastructures, Vol: 6, Pages: 1-20, ISSN: 2412-3811

This paper investigates the electrical, thermal and mechanical properties as well as the environmental performance of polymer cementitious composites (PCCs) as sustainable coating materials for underground power cables and as high-voltage insulators. Particular focus is placed on the optimised mix design and the effect of the manufacturing method on the performance of PCCs, incorporating liquid styrene and acrylic (SA) monomers, wollastonite and muscovite. Microstructural investigations, together with results from strength tests, indicate that the manufacturing method is a key performance parameter. Experimental results show that PCC mixes containing 25% SA emulsion, 12.5% wollastonite and no muscovite provide the most favourable dielectric properties from the mixes investigated. The PCC material has a dielectric strength up to 16.5 kV/mm and a dielectric loss factor lower than 0.12. Additional experiments also show that PCC has good thermal stability and thermal conductivity. The mechanical strength tests indicate that PCC specimens possess reliable strengths which are applicable in structural design. Environmental assessments also show that PCCs possess significantly lower embodied energy and embodied carbon than conventional plastic insulating materials.

Journal article

Mujdeci A, Bompa DV, Elghazouli A, 2021, Structural performance of composite steel rubberisedconcrete members under combined loading conditions, Eurosteel 2021

Conference paper

Goggins J, Jiang Y, Broderick B, Salawdeh S, O’Reilly G, Elghazouli A, Alwahsh H, Bogdanovic A, Rakicevic Z, Gjorgjiev I, Poposka A, Petreski B, Markovski Iet al., 2021, Shake Table Testing of Self Centring Concentrically Braced Frames, Eurosteel 2021

Conference paper

Elghazouli AY, Bompa DV, Mourad SA, Elyamani Aet al., 2021, In-plane lateral cyclic behaviour of lime-mortar and clay-brick masonry walls in dry and wet conditions, BULLETIN OF EARTHQUAKE ENGINEERING, Pages: 1-39, ISSN: 1570-761X

This paper presents an experimental investigation into the structural and material response of ambient-dry and wet clay-brick/lime-mortar masonry elements. In addition to cyclic tests on four large-scale masonry walls subjected to lateral in-plane displacement and co-existing compressive gravity load, the study also includes complementary tests on square masonry panels under diagonal compression and cylindrical masonry cores in compression. After describing the specimen details, wetting method and testing arrangements, the main results and observations are provided and discussed. The results obtained from full-field digital image correlation measurements enable a detailed assessment of the material shear-compression strength envelope, and permit a direct comparison with the strength characteristics of structural walls. The full load-deformation behaviour of the large-scale walls is also evaluated, including their ductility and failure modes, and compared with the predictions of available assessment models. It is shown that moisture has a notable effect on the main material properties, including the shear and compression strengths, brick–mortar interaction parameters, and the elastic and shear moduli. The extent of the moisture effects is a function of the governing behaviour and material characteristics as well as the interaction between shear and precompression stresses, and can lead to a loss of more than a third of the stiffness and strength. For the large scale wall specimens subjected to lateral loading and co-existing compression, the wet-to-dry reduction was found to be up to 20% and 11% in terms of stiffness and lateral strength, respectively, whilst the ductility ratio diminished by up to 12%. Overall, provided that the key moisture-dependent material properties are appropriately evaluated, it is shown that analytical assessment methods can be reliably adapted for predicting the response, in terms of the lateral stiffness, strength and overall load-de

Journal article

Ho HC, Guo YB, Xiao M, Xiao TY, Jin H, Yam MCH, Chung KF, Elghazouli AYet al., 2021, Structural response of high strength S690 welded sections under cyclic loading conditions, JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, Vol: 182, ISSN: 0143-974X

Journal article

Cedrón F, Elghazouli AY, 2021, Assessment and design considerations for single layer cylindrical lattice shells subjected to seismic loading, Structures, Vol: 31, Pages: 940-960, ISSN: 2352-0124

This paper examines the main considerations related to the seismic design and assessment of single layer steel cylindrical lattice shells, and offers recommendations for their practical application. Geometric configurations covering a wide range of rise to span ratios are considered within the investigation. An insight into the relative influence of seismic loading on shell design, in comparison to gravity conditions, is firstly provided through the use of digital parametric engineering procedures. This is followed by linear elastic response assessments which are used to propose a simplified procedure for estimating the internal seismic forces for the purpose of member sizing in early design stages. Suitable approaches for pushover analysis are then discussed and used to identify inherent plastic mechanisms. The results of incremental nonlinear dynamic analysis, using a suite of fourteen records, are also employed in order to validate the findings and to further assess the ultimate response under realistic seismic loading conditions. Based on the findings, representative ranges for behaviour factors and displacement modification coefficients are derived alongside discussions on their implementation within codified seismic design procedures. Apart from providing recommendations for simplified design approaches, the assessments presented in this paper can also be used to support detailed performance based guidelines as well as for informing geometry and size optimisation strategies.

Journal article

Bompa DV, Elghazouli AY, 2021, Behaviour of confined rubberised concrete members under combined loading conditions, Magazine of Concrete Research, Vol: 11, Pages: 555-573, ISSN: 0024-9831

This paper presents an experimental study into the fundamental response of reinforced concrete members, incorporating rubber particles obtained from recycled tyres, subjected to combined axial-bending loading conditions. Tests on confined circular members with and without internal hoops or external FRP sheets are described. The results show that the rubber particles enhance the confinement level activated, with confined-to-unconfined strength and deformation capacity ratios at least two folds those of conventional concrete members. The hoop-confined members provided with 30% rubber developed a typical reinforced concrete behaviour, with relatively limited deformation capacity in comparison to FRP-confined members. The external confinement enhanced substantially the ultimate rotation of members incorporating 30% rubber, with ductility factors reaching up to ten for relatively small eccentricity levels. An increase in rubber content to 60% had a detrimental effect on the axial capacity, but increased the ultimate rotation up to two folds in comparison to members with 30% rubber. Based on the test results, a design-oriented constitutive model for FRP-confined concrete and a variable confinement procedure for assessing the strength interaction of circular sections are proposed. The suggested procedures capture in a realistic manner the influence of rubber content on the strength and deformation characteristics of confined members.

Journal article

Mujdeci A, Bompa DV, Elghazouli AY, 2021, Confinement effects for rubberised concrete in tubular steel cross-sections under combined loading, Archives of Civil and Mechanical Engineering, Vol: 21, Pages: 1-20, ISSN: 1644-9665

This paper describes an experimental investigation into confinement effects provided by circular tubular sections to rubberised concrete materials under combined loading. The tests include specimens with 0%, 30% and 60% rubber replacement of mineral aggregates by volume. After describing the experimental arrangements and specimen details, the results of bending and eccentric compression tests are presented, together with complementary axial compression tests on stub-column samples. Tests on hollow steel specimens are also included for comparison purposes. Particular focus is given to assessing the confinement effects in the infill concrete as well as their influence on the axial–bending cross-section strength interaction. The results show that whilst the capacity is reduced with the increase in the rubber replacement ratio, an enhanced confinement action is obtained for high rubber content concrete compared with conventional materials. Test measurements by means of digital image correlation techniques show that the confinement in axial compression and the neutral axis position under combined loading depend on the rubber content. Analytical procedures for determining the capacity of rubberised concrete infilled cross-sections are also considered based on the test results as well as those from a collated database and then compared with available recommendations. Rubber content-dependent modification factors are proposed to provide more realistic representations of the axial and flexural cross-section capacities. The test results and observations are used, in conjunction with a number of analytical assessments, to highlight the main parameters influencing the behaviour and to propose simplified expressions for determining the cross-section strength under combined compression and bending.

Journal article

Bompa DV, Xu B, Elghazouli AY, 2021, Constitutive modelling and mechanical properties of cementitious composites incorporating recycled vinyl banner plastics, Construction and Building Materials, Vol: 275, ISSN: 0950-0618

This paper describes an experimental study, which has been lacking to date, into the mechanical properties of cementitious composites incorporating granules and fibres from recycled Reinforced PVC (RPVC) banners. A detailed account of over 140 tests on cylindrical, cubic and prismatic samples tested in compression and flexure, with up to 20% replacement of mineral aggregates, is given. Based on the test results, the uniaxial properties of selected recycled materials are examined in conjunction with a detailed characterisation of the RPVC granule size and geometry. Experimental measurements using digital image correlation techniques enable a detailed interpretation of the full constitutive response in terms of compression stress-strain behaviour and flexural stress-crack opening curves, as well as key mechanical parameters such as strength, elastic modulus and fracture energy. It is shown that the mechanical properties decrease proportionally with the amount of RPVC. For each 10% increment of volumetric replacement of mineral aggregates, the compressive strength is halved whilst the flexural strength is reduced by about 30% compared to their conventional counterparts. The reduction in strength is counterbalanced by an improved ductility represented by a favourable post-peak response in compression and an enhanced flexural softening and post-cracking performance. Smaller particles, with a relatively long acicular or triangular geometry, exhibited better behaviour as these acted as fibres with improved bond properties in comparison with intermediate and large size granules. The test results and observations enable the definition of a series of expressions to determine the mechanical properties of cementitious materials incorporating RPVC and other waste plastics. These expressions are then used as a basis for an analytical model for assessing the compressive and tensile stress-strain response of such materials. Validations carried out against the tests undertaken in th

Journal article

Bravo-Haro MA, Virreira JR, Elghazouli AY, 2021, Inelastic displacement ratios for non-structural components in steel framed structures under forward-directivity near-fault strong-ground motion, Bulletin of Earthquake Engineering, Vol: 19, Pages: 2185-2211, ISSN: 1570-761X

This paper describes a detailed numerical investigation into the inelastic displacement ratios of non-structural components mounted within multi-storey steel framed buildings and subjected to ground motions with forward-directivity features which are typical of near-fault events. The study is carried out using detailed multi-degree-of-freedom models of 54 primary steel buildings with different structural characteristics. In conjunction with this, 80 secondary non-structural elements are modelled as single-degree-of-freedom systems and placed at every floor within the primary framed structures, then subsequently analysed through extensive dynamic analysis. The influence of ground motions with forward-directivity effects on the mean response of the inelastic displacement ratios of non-structural components are compared to the results obtained from a reference set of strong-ground motion records representing far-field events. It is shown that the mean demand under near-fault records can be over twice as large as that due to far-fault counterparts, particularly for non-structural components with periods of vibration lower than the fundamental period of the primary building. Based on the results, a prediction model for estimating the inelastic displacement ratios of non-structural components is calibrated for far-field records and near-fault records with directivity features. The model is valid for a wide range of secondary non-structural periods and primary building fundamental periods, as well as for various levels of inelasticity induced within the secondary non-structural elements.

Journal article

Bravo-Haro MA, Ding X, Elghazouli A, 2021, MEMS-based low-cost and open-source accelerograph for earthquakestrong-motion, Engineering Structures, Vol: 230, ISSN: 0141-0296

This paper describes a sensing technique that has been entirely built from off-the-shelf electronic components, with the aim of providing its construction and programming guidelines as an open-source platform which can be continuously updated. The assessments carried out in this investigation indicate that the proposed sensor is suitable for deployment as an accelerograph for seismic monitoring of structural systems. The results show low levels of self- noise, considering the nature of the MEMS analogue accelerometer embedded in the sensor. The amplitude transfer functions exhibit a flat behaviour for the full range of frequencies tested, whose boundaries were limited by the installed capacity within the laboratory. However, this flat behaviour is expected to be coherent up to the resonant frequency of the MEMS accelerometer, whose absolute value is much higher than the bandwidth of frequencies of interest for seismologists and structural earthquake engineers. The clipping tests demonstrate a high linearity of the amplitude transfer function from low acceleration levels up to the vicinity of the maximum nominal recordable acceleration of ±3 g at which a typical roll-off is observed. Under long-time operations, the sensor produces a robust performance, maintaining a steady pace of sampling. The performance of the sensor was finally tested considering non-stationary signals, using a linear shake table to reproduce a wide ensemble of strong-motion recordings from actual earthquakes. Intensity measures of strong-motion commonly used in earthquake engineering were appraised, such as horizontal spectral acceleration, Arias Intensity, and transient peaks of response.

Journal article

Khalil Z, Martinez-Paneda E, Elghazouli A, 2020, A PHASE-FIELD APPROACH FOR MODELLING CYCLIC FATIGUEINDUCEDFRACTURE IN DISSIPATIVE STEEL COMPONENTS, 17th World Conference on Earthquake Engineering, 17WCEE

Conference paper

Elghazouli A, Bompa DV, Mourad SA, Elyamani Aet al., 2020, EXPERIMENTAL CYCLIC RESPONSE OF DRY AND WET MASONRY WALLSINCORPORATING CLAY BRICKS AND LIME MORTAR, 17th World Conference on Earthquake Engineering, 17WCEE

Conference paper

Bompa DV, Elghazouli A, 2020, Shear-compression failure envelopes for clay brick lime mortar masonry under wet and dry conditions, International Conference on Protection of Historical Constructions

Conference paper

Elghazouli A, Bompa DV, Mourad SA, Elyamani Aet al., 2020, Structural behaviour of clay brick lime mortar masonry walls under lateral cyclic loading in dry and wet conditions, International Conference on Protection of Historical Constructions

Conference paper

Chen Y, Huo J, Chen W, Hao H, Elghazouli AYet al., 2020, Experimental and numerical assessment of welded steel beam-column connections under impact loading, Journal of Constructional Steel Research, Vol: 175, Pages: 1-15, ISSN: 0143-974X

This paper describes experimental and numerical investigations into the behavior of fully welded steel beam-to-column connections subjected to static and dynamic impact loads. The experimental assessment includes static and dynamic tests on four large-scale specimens, depicting two connection configurations incorporating different weld access-hole details. After providing a detailed account of the specimen details and testing arrangements, the main results and observations are presented and discussed. Particular emphasis is placed on assessing the static and dynamic forces, displacement response, and energy dissipation. Additionally, in order to provide further insights into the performance, detailed nonlinear dynamic finite element simulations are carried out and compared against the experimental results. The validated finite element models are employed in order to examine the effects of the local weld detail on the behavior of the connection, in terms of sectional internal forces and energy absorption under impact loading conditions. The numerical model is also adopted within a parametric assessment to develop a simplified relationship between the plastic rotation of the connection and the input impact energy, for use in practical application.

Journal article

Bompa DV, Elghazouli AY, 2020, Experimental and numerical assessment of the shear behaviour of lime mortar clay brick masonry triplets, Construction and Building Materials, Vol: 262, Pages: 1-17, ISSN: 0950-0618

This study investigates the fundamental shear response of masonry triplets incorporating fired-clay bricks and hydraulic lime mortars. It examines the behaviour under ambient-dry and wet conditions, corresponding to 48 h submersion in water, as well as the effectiveness of strengthening with fibre reinforced polymer (FRP) laminates and glass fibre meshes (GFM). After describing the materials, mix designs and specimen details, the main results from 50 triplet tests subjected to shear and normal pre-compression are presented. Digital image correlation measurement techniques, which are employed in order to obtain a detailed insight into the shear behaviour, enable clear identification and quantification of the main failure modes and response characteristics of the brick-mortar interfaces. The results show that the shear strength of wet triplets was about 20% lower on average than of those in dry conditions. Specimens provided with FRP sheets offered a higher strength enhancement than those with GFM. The strength increase using FRP was in the range of 16.6%–185.8% compared with the non-strengthened dry counterpart, depending on the laminate layout and normal stress level. In contrast, the strength increase using GFM, in conjunction with a mortar overlay, was typically less than 10% compared with the non-strengthened dry counterpart. A significantly higher strength contribution from both FRP and GFM was obtained for elements without pre-compression. Although the strength enhancement using GFM was generally modest, such strengthening is activated gradually leading to a relatively ductile interfacial behaviour in comparison with FRP. In order to provide further insights into the behaviour, complementary nonlinear numerical simulations are undertaken, using the key parameters obtained from the tests. The numerical models employ detailed surface-based cohesive-contact approaches, with due account for inelastic damage at the masonry interfaces, and damage-plasticity mod

Journal article

Guo YB, Ho HC, Chung KF, Elghazouli AYet al., 2020, Cyclic deformation characteristics of S355 and S690 steels under different loading protocols, Engineering Structures, Vol: 221, Pages: 1-19, ISSN: 0141-0296

Despite of excellent high strength to self-weight ratios of the S690 steels, when compared with the S355 steels, there is a widespread concern regarding the ductility of the S690 steels. It is generally considered that the ductility of the S690 steels is significantly lower than that of the S355 steels – this is the general understandings the authors attempt to investigate.This paper presents an experimental investigation into cyclic deformation characteristics of both S355 and S690 steels through low-cycle high-strain cyclic tests with two different loading protocols. A detailed account of the results of 32 cyclic tests on both the S355 and the S690 funnel-shaped coupons is presented. Effects of four different target strains and two different loading frequencies are also examined in details. For the ranges of loading protocols, strain amplitudes, and frequencies considered, the hysteretic responses of these coupons of the two steels are compared directly in terms of engineering stress–strain curves based on their nominal diameters. Microstructures of the fractured coupons of the two steels are also identified for comparison.Contrary to the general understandings, it is demonstrated that the high strength S690 steels do have a good ductility under both monotonic and cyclic actions. Moreover, depending on specific loading protocols and target strains, the cyclic deformation characteristics of the S690 steels are demonstrated to be superior to those of the S355 steels in terms of the number of cycles completed prior to failure and their corresponding energy dissipation characteristic under various target strains up to ±10.0%.The findings of this experimental investigation highlight the importance of establishing ductility requirements and cyclic deformation characteristics for the high strength S690 steels in accordance with specifically designed cyclic tests rather than relying solely on conventional monotonic tensile tests.

Journal article

Goggins J, Jiang Y, Broderick BM, Salawdeh S, O’Reilly GJ, Elghazouli A, Alwahsh H, Bogdanovic A, Rakicevic Z, Gjorgjiev I, Poposka A, Petreski B, Markovski Iet al., 2020, Experimental Testing of a Novel Self-Centring Steel Braced Frame on the Shake Table in Dynlab-IZIIS, 17 World Conference on Earthquake Engineering

Conference paper

Bravo-Haro M, Elghazouli A, 2020, Inelastic Displacement Ratios for Non-Structural Components in Steel Framed Structures, 17 World Conference on Earthquake Engineering

Conference paper

Liapopoulou M, Bravo-Haro M, Elghazouli A, 2020, The Role of Strong Motion Duration and Acceleration Pulses in Structural Collapse, 17 World Conference on Earthquake Engineering

Conference paper

Sahin B, Bravo-Haro M, Elghazouli A, 2020, Influence of Composite Action on the Inelastic Behaviour of Composite Steel-Concrete Members, 17 World Conference on Earthquake Engineering

Conference paper

Liapopoulou M, BravoHaro MA, Elghazouli AY, 2020, The role of ground motion duration and pulse effects in the collapse of ductile systems, Earthquake Engineering & Structural Dynamics, Vol: 49, Pages: 1051-1071, ISSN: 0098-8847

The seismic collapse capacity of ductile single‐degree‐of‐freedom systems vulnerable to P‐Δ effects is investigated by examining the respective influence of ground motion duration and acceleration pulses. The main objective is to provide simple relationships for predicting the duration‐dependent collapse capacity of modern ductile systems. A novel procedure is proposed for modifying spectrally equivalent records, such that they are also equivalent in terms of pulses. The effect of duration is firstly assessed, without accounting for pulses, by assembling 101 pairs of long and short records with equivalent spectral response. The systems considered exhibit a trilinear backbone curve with an elastic, hardening and negative stiffness segment. The parameters investigated include the period, negative stiffness slope, ductility and strain hardening, for both bilinear and pinching hysteretic models. Incremental dynamic analysis is employed to determine collapse capacities and derive design collapse capacity spectra. It is shown that up to 60% reduction in collapse capacity can occur due to duration effects for flexible bilinear systems subjected to low levels of P‐Δ. A comparative evaluation of intensity measures that account for spectral shape, duration or pulses, is also presented. The influence of pulses, quantified through incremental velocity, is then explicitly considered to modify the long records, such that their pulse distribution matches that of their short spectrally equivalent counterparts. The results show the need to account for pulse effects in order to achieve unbiased estimation of the role of duration in flexible ductile systems, as it can influence the duration‐induced reduction in collapse capacity by more than 20%.

Journal article

Xu B, Bompa DV, Elghazouli AY, 2020, Cyclic stress–strain rate-dependent response of rubberised concrete, Construction and Building Materials, Vol: 254, Pages: 1-14, ISSN: 0950-0618

This paper presents an experimental investigation into the constitutive response of rubberised concrete materials under monotonic and cyclic compression. After describing the test specimens and experimental arrangement, a detailed account of the stress–strain response of rubberised concrete materials, as well as their reference high strength conventional concrete, is given. The volumetric rubber content is varied between 0 and 40% of both fine and coarse aggregates. Both monotonic and cyclic loading conditions are considered for comparison, and three strain rate levels, simulating static, moderate and severe seismic action, are examined. The increase in rubber content is shown to have a detrimental effect on the stiffness and strength, as expected. However, with the increase in rubber content, rubberised concrete materials are shown to exhibit improved compressive recovery under cyclic loading, coupled with a higher energy accumulation rate, enhanced inter-cycle stability and lower inter-cycle degradation. It is also shown that the increase in strain rate, from static to severe seismic, leads to a notable increase in the stiffness and strength, with these enhancements becoming less significant with the increase in rubber content. Based on the results and observations, expressions for determining the unloading stiffness and residual strain, as a function of rubber content and strain rate, are proposed within the ranges considered. The suggested relationships enable the characterisation of rubberised concrete materials within widely used cyclic constitutive models.

Journal article

Bompa DV, Elghazouli AY, 2020, Compressive behaviour of fired-clay brick and lime mortar masonry components in dry and wet conditions, Materials and Structures, Vol: 53, Pages: 1-21, ISSN: 1359-5997

This paper examines the fundamental mechanical properties of masonry elements incorporating fired-clay bricks and hydraulic lime mortars under ambient-dry and wet conditions, corresponding to 48 h submersion in water. In addition to complementary material characterisation assessments, two types of specimens are tested: cylindrical cores in compression, and wall elements in compression. Overall, a detailed account of more than 50 tests is given. Apart from conventional measurements, the use of digital image correlation techniques enables a detailed assessment of the influence of moisture on the constitutive response, confinement effects and mechanical properties of masonry components. The uniaxial compressive strengths of wet brick elements and brick–mortar components, resulting from tests on cylindrical cores with height-to-depth ratios of around two, are shown to be 13–18% lower than those in ambient-dry conditions. The tests also show that enhanced confinement levels in brick units mobilise 67–92% higher strengths than in the corresponding unconfined cylinders. Moreover, experimental observations indicate that the presence of significant confinement reduces the influence of moisture on the mechanical properties as a function of the brick and mortar joint thickness and their relative stiffness. As a result, the failure of wet masonry walls in compression is found to be only marginally lower than those in ambient-dry conditions. Based on the test results, the influence of moisture on the constitutive response and mechanical properties of masonry components is discussed, and considerations for practical application are highlighted.

Journal article

Li Z, Tan Y, Huo J, Liu Y, Elghazouli AYet al., 2020, Behaviour of Fire-Exposed Reinforced Concrete Joints with Varying Anchorage Details Subjected to Exterior Column Removal, FIRE TECHNOLOGY, Vol: 56, Pages: 1443-1464, ISSN: 0015-2684

Journal article

Bravo-Haro MA, Liapopoulou M, Elghazouli AY, 2020, Seismic collapse capacity assessment of SDOF systems incorporating duration and instability effects, Bulletin of Earthquake Engineering, Vol: 18, Pages: 3025-3056, ISSN: 1570-761X

This paper presents a detailed investigation into the seismic response of non-deteriorating and deteriorating single degree-of-freedom systems controlled by P−Δ effects, with due account for the influence of earthquake duration. In order to isolate the effect of duration from other ground motion characteristics, 77 pairs of records with equivalent spectral shapes are considered in the study. The structural characteristics examined include the structural period, applied gravity loading, post-yield stiffness, viscous damping, material hysteretic behaviour, as well as the level of cyclic deterioration within the pinching systems. Detailed incremental dynamic analyses are carried out, considering an intensity measure corresponding to the spectral acceleration at the structural period of vibration of the system. Based on the incremental dynamic analysis results, predictive relationships are proposed for determining the structural collapse capacity, accounting for the influence of key parameters including instability and duration effects. The median and dispersion of the collapse capacity distribution embedded in the predictive models are also presented. The effect of duration is shown to increase with longer structural periods and to decrease with higher P−Δ levels. The more rapid instigation of dynamic instability in relatively stiff systems is also shown to reduce their comparative sensitivity to variations in ground motion characteristics. Overall, it is indicated that disregarding the influence of duration could lead to over-estimations of up to 50% in the collapse capacity. The paper concludes with a discussion of other sources of structural damage that instigate collapse when using records with equivalent spectral shape but without especial consideration for duration effects.

Journal article

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