Publications
388 results found
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.
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.
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.
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
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.
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.
Khalil Z, Elghazouli AY, Martínez-Pañeda E, 2021, A generalised phase field model for fatigue crack growth in elastic-plastic solids with an efficient monolithic solver., CoRR, Vol: abs/2110.10425
Elghazouli A, Bompa DV, Mourad SA, et al., 2020, EXPERIMENTAL CYCLIC RESPONSE OF DRY AND WET MASONRY WALLSINCORPORATING CLAY BRICKS AND LIME MORTAR, 17th World Conference on Earthquake Engineering, 17WCEE
Khalil Z, Martínez-Pañeda E, Elghazouli A, 2020, A phase-field approach for modelling cyclic fatigue-induced fracture in dissipative steel components, 17th World Conference on Earthquake Engineering, 17WCEE
Chen Y, Huo J, Chen W, et 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.
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
Guo YB, Ho HC, Chung KF, et 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.
Bravo-Haro M, Elghazouli A, 2020, Inelastic Displacement Ratios for Non-Structural Components in Steel Framed Structures, 17 World Conference on Earthquake Engineering
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
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
Goggins J, Jiang Y, Broderick BM, et 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
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%.
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.
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.
Li Z, Tan Y, Huo J, et 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
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.
Shen M-H, Chung K-F, Elghazouli AY, et al., 2020, Structural behaviour of stud shear connections in composite floors with various connector arrangements and profiled deck configurations, Engineering Structures, Vol: 210, Pages: 1-20, ISSN: 0141-0296
This paper investigates the structural behaviour of stud shear connections in composite floors with various connector arrangements and profiled deck configurations. The numerical investigation adopts a number of advanced finite element models which have been carefully calibrated against standard push-out tests conducted by the authors. In order to capture the complex interactions that take place between the concrete and the headed shear studs, a number of distinctive load transfer mechanisms within the solid concrete and the profiled composite slabs are identified and discussed. Detailed parametric studies are then undertaken using the calibrated models for the purpose of quantifying the shear resistance and deformation characteristics for connections with various stud and deck arrangements. A configuration parameter β is proposed for use in conjunction with the reduction factor kt given in EN 1994-1-1 to incorporate the effects of installation positions of headed shear studs and trough widths of profiled decks as well as the presence of longitudinal stiffeners if any. It is shown that the values of β are in the range of 0.55 to 1.0, which are significantly smaller than those commonly allowed for in the design of stud shear connections in composite floors.
Bompa DV, Elghazouli AY, 2020, Nonlinear numerical simulation of punching shear behavior of reinforced concrete flat slabs with shear-heads, Frontiers of Structural and Civil Engineering, Vol: 14, Pages: 331-356, ISSN: 2095-2449
This paper examines the structural response of reinforced concrete flat slabs, provided with fully-embedded shear-heads, through detailed three-dimensional nonlinear numerical simulations and parametric assessments using concrete damage plasticity models. Validations of the adopted nonlinear finite element procedures are carried out against experimental results from three test series. After gaining confidence in the ability of the numerical models to predict closely the full inelastic response and failure modes, numerical investigations are carried out in order to examine the influence of key material and geometric parameters. The results of these numerical assessments enable the identification of three modes of failure as a function of the interaction between the shear-head and surrounding concrete. Based on the findings, coupled with results from previous studies, analytical models are proposed for predicting the rotational response as well as the ultimate strength of such slab systems. Practical recommendations are also provided for the design of shear-heads in RC slabs, including the embedment length and section size. The analytical expressions proposed in this paper, based on a wide-ranging parametric assessment, are shown to offer a more reliable design approach in comparison with existing methods for all types of shear-heads, and are suitable for direct practical application.
Bompa DV, Elghazouli AY, 2020, Stress-strain response and practical design expressions for FRP-confined recycled tyre rubber concrete, Construction and Building Materials, Vol: 237, ISSN: 0950-0618
This paper presents an experimental programme on the response of fibre reinforced polymer (FRP) confined circular rubberised concrete (RuC) members in compression. After describing the constituent materials and testing arrangement, a detailed account of the complete stress–strain response of FRP-confined high strength conventional concrete materials (CCM) and RuC in uniaxial compression is provided. The parameters directly investigated through experimental assessment are the rubber content, namely 30% and 60% by volume of both fine and coarse aggregates, and the number of confinement layers which varies from 0 to 4. Experimental observations indicate that the confined compressive strength typically increases in a largely proportional manner with the unconfined compressive strength, whilst the confined axial strain at ultimate tends to increase with the rubber content. Confined-to-unconfined strength ratios above 9 and confined ultimate strain-to-unconfined crushing strain ratios above 40, are obtained for concrete with 60% rubber and four layers of confinement. These values are higher by factors of about 3.2 and 4.5 in comparison to the conventional reference concrete, respectively. The test results and observations enable the development of a series of design expressions to estimate the stress–strain response of circular RuC specimens passively confined with FRP sheets, with due account for the influence of rubber content. Validations performed against the material tests carried out in this paper, as well as those from previous studies on RuC and CCM with FRP confinement, indicate that the proposed expressions offer reliable predictions of the mechanical properties of FRP-confined members.
MartinezPaneda M, Elghazouli AY, 2020, An integrated damping system for tall buildings, The Structural Design of Tall and Special Buildings, Vol: 29, Pages: 1-26, ISSN: 1541-7794
This paper proposes an integrated damping system that aims at providing relatively high damping levels through the mobilization of a proportion of the structure's own mass. This offers significantly higher mass levels and, consequently, considerably more damping compared to conventional tuned mass dampers. Fluid viscous dampers are used to control accelerations in parallel with springs to resist the static loads applied to the moving mass. The advantages of employing relatively large mass levels in achieving considerable damping and reducing sensitivity to tuning are first analyzed using an idealized two degree of freedom structural representation. This is then followed by a description of the proposed “integrated damping system,” which is illustrated through a case study of a 250‐m tall building. The benefits of the proposed damping system are demonstrated through several numerical parametric assessments, as well as a selected suite of earthquake records. For the adopted case study, it is shown that, besides reducing the level of perceivable accelerations, the use of the suggested arrangement can offer an equivalent damping exceeding 50% of the critical damping, resulting in more than 40% reduction in the wind loads as well as over 60% reduction in displacement and acceleration response under seismic excitations.
Xu B, Bompa DV, Elghazouli AY, et al., 2020, Numerical assessment of reinforced concrete members incorporating recycled rubber materials, Engineering Structures, Vol: 204, ISSN: 0141-0296
This paper is concerned with the inelastic behaviour of reinforced concrete beam-column members incorporating rubber from recycled tyres. Detailed three-dimensional nonlinear numerical simulations and parametric assessmentsare carried out using finite element analysis in conjunction with concrete damage plasticity models. Validationsof the adopted nonlinear finite element procedures arecarried out against experimental results from a series of tests involvingconventional and rubberised concrete flexural members and varying levels of axial load. The influence of key parameters, such as the concrete strength, rubber content, reinforcement ratio and level of axial load, on the performance of such members, is then examined in detail.Based on the results, analytical models are proposed for predicting the strength interaction as well as the ductility characteristicsof rubberised reinforced concrete members. The findings permit the development ofdesignexpressionsfor determiningthe ultimate rotation capacityof members,usinga rotation ductility parameter, or through a suggestedplastic hinge assessment procedure. Theproposedexpressionsare shown to offer reliable estimates of strength and ductilityof reinforced rubberised concrete members,whichare suitable for practical application and implementation in codified guidance.
Xu B, Bompa DV, Elghazouli AY, 2020, Monotonic and cyclic compressive properties of rubberised concrete, Pages: 109-117
This paper examines the fundamental constitutive response of concrete materials incorporating relatively high proportions of recycled tyre rubber particles. A series of experimental studies on rubberised concrete specimens, subjected to monotonic and cyclic compression, are presented. The testing arrangements, material details and main observations are described. The monotonic tests allow for an in-depth understanding of the effects rubber particles have on the properties of concrete, including on the compressive strength, elastic modulus and crushing strain, whilst the cyclic tests assess the unloading and reloading properties of rubberised concrete. The increase of rubber content is shown to reduce the stiffness and strength, but improve the ductility, as well as the inter-cycle stability and compressive recovery properties under cyclic loading. The test results enable the definition of a set of analytical expressions describing the complete stress-strain envelope and key cyclic constitutive parameters of rubberised concrete as a function of the volumetric rubber ratio. Along with other expressions for direct shear and concrete-rebar interface response, the proposed constitutive equations can be employed for non-linear modelling of structural rubberised concrete.
Xu B, Dan Bompa V, Elghazouli AY, 2020, Monotonic and cyclic compressive properties of rubberised concrete, Pages: 109-117, ISSN: 2617-4820
This paper examines the fundamental constitutive response of concrete materials incorporating relatively high proportions of recycled tyre rubber particles. A series of experimental studies on rubberised concrete specimens, subjected to monotonic and cyclic compression, are presented. The testing arrangements, material details and main observations are described. The monotonic tests allow for an in-depth understanding of the effects rubber particles have on the properties of concrete, including on the compressive strength, elastic modulus and crushing strain, whilst the cyclic tests assess the unloading and reloading properties of rubberised concrete. The increase of rubber content is shown to reduce the stiffness and strength, but improve the ductility, as well as the inter-cycle stability and compressive recovery properties under cyclic loading. The test results enable the definition of a set of analytical expressions describing the complete stress-strain envelope and key cyclic constitutive parameters of rubberised concrete as a function of the volumetric rubber ratio. Along with other expressions for direct shear and concrete-rebar interface response, the proposed constitutive equations can be employed for non-linear modelling of structural rubberised concrete.
Sirumbal-Zapata LF, Malaga Chuquitaype C, Elghazouli A, 2019, Experimental assessment and damage modelling of hybrid timber beam-to-steel column connections under cyclic loads, Engineering Structures, Vol: 200, ISSN: 0141-0296
This paper presents an experimental and numerical study on the behaviour of timber beam-to-steel column connections under cyclic loads. Special attention is given to the accumulation of damage in the timber com- ponents and to its simulation. To this end, the fundamental nonlinear cyclic response of three specimens involving di↵erent configurations of top and seat angle connections with long bolts is examined. The experi- mental set-up, connection details and material properties are introduced first, followed by a detailed account of the testing procedure and results. The experimental outcomes enable a direct comparative assessment of the connection strength, hysteretic response, joint ductility, failure mode and energy dissipation capacity. In addition, finite element analyses employing a newly proposed damage-plasticity constitutive model of wood are presented together with a detailed description of the adopted modelling approach. The numerical output of these simulations at the local level, expressed in terms of strains and damage indices, is discussed and com- pared against the experimental measurements of local damage in the wood obtained through Digital Image Correlation (DIC) techniques. It is demonstrated that the connections under consideration are able to sus- tain their bending capacity without a significant deterioration in their sti↵ness or strength even up to large levels of deformation and several repetitions of loading cycles. Besides, the results and discussion presented in this paper support the conventional definition of global failure as a post-peak strength reduction higher than 20% of the capacity but so long as the strength measurements are obtained from the stabilized envelope curves of the specimens. The applicability of damage mechanics concepts to provide a reliable prediction of crack zones and damage accumulation in timber structures under the action of cyclic loads is also highlighted.
Cedron F, Elghazouli A, 2019, Seismic performance of single layer steel cylindrical lattice shells, Journal of Constructional Steel Research, Vol: 163, ISSN: 0143-974X
This paper examines the elastic and inelastic seismic behaviour of single layer steel cylindrical lattice shells. The main dynamic characteristics for this form of structure are firstly examined through a parametric assessment, which also leads to proposed expressions for estimating the fundamental period and mode of vibration. The seismic response of five typical shell configurations, representing a wide range of rise to span ratios, is then assessed within the linear elastic range under selected earthquake excitations. Particular focus is given to the relative influence of the horizontal and vertical seismic components on the internal actions. In order to provide a means for evaluating the underlying inelastic behaviour, a simple pushover approach, which is suitable for this structural form, is suggested using the forces obtained from the fundamental mode shape. The peak angle change is proposed as a damage parameter within the nonlinear analysis for characterising the inelastic global and local demands in shells of different geometries. Incremental dynamic analysis is subsequently carried out in order to evaluate the detailed nonlinear time history response. The results provide detailed insights into the influence of the horizontal and vertical excitations on the nonlinear seismic response, and illustrate the suitability of the peak angle change as an inelastic deformation measure for shells of different geometric configurations. The main findings from the linear and nonlinear assessments are highlighted within the discussions, with a view to providing guidance for performance based assessment procedures as well as simplified design approaches.
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