Imperial College London

DrDanBompa

Faculty of EngineeringDepartment of Civil and Environmental Engineering

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Publications

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69 results found

Sabău M, Bompa DV, Silva LFO, 2021, Comparative carbon emission assessments of recycled and natural aggregate concrete: Environmental influence of cement content, Geoscience Frontiers, Vol: 12, Pages: 101235-101235, ISSN: 1674-9871

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

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

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

Corbu O, Bompa DV, Szilagyi H, 2021, Eco-efficient cementitious composites with large amounts of waste glass and plastic, Proceedings of the Institution of Civil Engineers - Engineering Sustainability, Pages: 1-11, ISSN: 1478-4629

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

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

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

Ţibea C, Bompa DV, 2020, Ultimate shear response of ultra-high-performance steel fibre-reinforced concrete elements, Archives of Civil and Mechanical Engineering, Vol: 20, Pages: 1-16, ISSN: 1644-9665

This paper examines the experimental performance of ultra-high-performance steel fibre-reinforced concrete (UHPSFRC) beams subjected to loads at relatively low shear span-to-depth ratios. The results and observations from six tests provide a detailed insight into the ultimate response including shear strength and failure mode of structural elements incorporating various fibre contents. The test results showed that a higher fibre content results in an increase in ultimate capacity and some enhancement in terms of ductility. Detailed nonlinear numerical validations and sensitivity studies were also undertaken in order to obtain further insights into the response of UHPSFRC beams, with particular focus on the influence of the shear span-to-depth ratio, fibre content and flexural reinforcement ratio. The parametric investigations showed that a reduction in shear span-to-depth ratio results in an increase in the member capacity, whilst a reduction in the flexural reinforcement ratio produces a lower ultimate capacity and a relatively more flexible response. The test results combined with those from numerical simulations enabled the development of a series of design expressions to estimate the shear strength of such members. Validations were performed against the results in this paper, as well as against a collated database from previous experimental studies.

Journal article

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.

Journal article

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.

Journal article

Xu B, Bompa DV, Elghazouli AY, Ruiz-Teran AM, Stafford PJet 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.

Journal article

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.

Conference paper

Xu B, Li H, Chen J, Bompa DVet al., 2020, Performance characteristics of polymer cement mortars, Pages: 358-366

This paper presents a series of experimental investigations on the microstructure, mechanical, thermal and dielectric, properties of Polymer Cement Mortars (PCMs). Liquid styrene and acrylic (SA) monomers, wollastonite and muscovite are added to improve the thermal and electrical insulation properties. Particular focus is given to the optimised mix design and the effect of the manufacturing method on the performance of PCMs. The microstructural investigations along with the mechanical and dielectric strength tests indicate a significant influence of manufacturing method on the insulating properties of PCMs. The test results also show that the polymer components greatly reduce the dielectric loss of PCMs compared to conventional concrete. Additional experiments highlight that PCM has better thermal stability and thermal conductivity compared to other types of commonly used insulating materials, suggesting that PCMs have appropriate properties for application as insulating components. The mechanical test results show that PCMs possess the compressive and tensile strengths of structural elements, indicating potential applications of such composite as cable coatings, repair grout or textile reinforced overlays.

Conference paper

Bompa DV, Elghazouli AY, 2019, Properties of hydraulic lime mortars subjected to dry-wet cycles, Publisher: Imperial College London

Report

Bompa DV, Elghazouli AY, 2019, Compressive and shear behaviour of clay brick - lime mortar components in wet and dry conditions, London, UK, Publisher: Imperial College London

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Bompa DV, Elghazouli AY, 2019, Seismic behaviour and design of steel reduced beam section connections, SECED 2019 Conference

Conference paper

Pilakoutas K, Papastergiou P, Hu H, Alsaif A, Huang S, Guadagnini M, Hajirasouliha I, Raffoul S, Angelakopoulos H, Bompa D, Elghazouli Aet al., 2019, Innovative reuse of all end-of-life tyre components in concrete: Main technological achievements, fib-IWAMISSE-2019, CEB-fib International Workshop on Advanced Materials and Innovative Systems in Structural Engineering, Pages: 61-72

Conference paper

Bogdan T, Bompa DV, Elghazouli AY, Nunez E, Eatherthon M, Leon Ret al., 2019, Experimental and numerical simulations on RBS connections incorporating large sections, COMPDYN 2019 7th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis (eds.), Pages: 5802-5812, ISSN: 2623-3347

Recent experimental tests have shown that RBS connections incorporating Jumbo specimens meet the current seismic design qualification protocols, allowing to further extend the current seismic provisions for prequalified steel connections with possible applications of heavy steel sections beyond their current use in ultra-tall buildings. The experimental results and observations described in this paper enabled a better understanding of the structural behaviour of RBS connections made of heavy structural sections for application in seismic regions. How-ever, the results indicate that geometrical and material effects need to be carefully considered when designing welded RBS connections incorporating large steel profiles. To better interpret the experimental results, extensive detailed non-linear finite element simulations are conduct-ed on the entire series of tests, comprising of three large-scale specimens with distinct sizes. The analyses intend to clarify the scale effects that influence the performance of these connections, both at material and geometric level, and particularly to understand the balance in deformation between the column panel zones and the reduced beam section and level of stress within the main connection components. It is shown that the numerical models for all three specimens reproduce accurately the overall load-deformation and moment-rotation time history.

Conference paper

Bompa DV, Elghazouli AY, 2019, Creep properties of recycled tyre rubber concrete, Construction and Building Materials, Vol: 209, Pages: 126-134, ISSN: 0950-0618

This paper investigates the creep response and long-term strength properties of unconfined and FRP-confined concrete materials incorporating relatively high proportions of recycled tyre rubber particles. The high-strength reference conventional concrete, from which the rubberised concrete is derived, is also examined for comparison purposes. After discussing fundamental characteristics of creep behaviour, this study describes an experimental investigation in which three groups of concrete specimens are subjected to sustained uniaxial compressive stress, in the range of about 20% of the estimated strength, for a period of over a year. The test results indicate that both confined and unconfined rubberised concrete materials tend to develop higher creep coefficients by about 53% and 20%, respectively, in comparison to their reference conventional concrete.

Journal article

Bompa DV, Elghazouli AY, 2019, Axial-bending interaction of high deformability FRP-confined circular concrete members, ACIC 2019 Advanced Composites in Construction

Conference paper

Bompa D, Elghazouli A, 2019, Axial-bending Interaction of High Deformability FRP-confined CircularConcrete Members, International Conference on Advanced Composites in Construction

Conference paper

Bompa DV, Elghazouli AY, 2019, Nonlinear numerical simulation of punching shear behaviour of reinforced concrete flat slabs with shear-heads, Frontiers of Structural and Civil Engineering, 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 influenceof 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.

Journal article

Bompa DV, Elghazouli AY, 2019, Elevated temperature characteristics of steel reinforcement incorporating threaded mechanical couplers, Fire Safety Journal, Vol: 104, Pages: 8-21, ISSN: 0379-7112

This paper presents an experimental study into the influence of elevated temperatures on the mechanical properties of hot-rolled steel reinforcement which is spliced using two alternative types of threaded couplers. The investigation includes tests performed under steady-state and transient elevated temperature conditions for reinforcement bars of 16 mm and 20 mm diameter. For comparison purposes, tests carried out under ambient conditions and for non-spliced reinforcement bars are also included in the study. After describing the experimental arrangement and instrumentation, including purpose-adapted digital image correlation techniques, a detailed account of the test results is given. In addition to offering a direct evaluation of the temperature-dependent stiffness and strength properties, the test results provide an assessment of the complete stress-strain response. The strain hardening and ductility properties are also determined as a function of temperature for both spliced and non-spliced specimens. It is shown that the presence of couplers typically influences the ductility characteristics of threaded splices at elevated temperature as a function of the type and geometry of the couplers, whilst the stiffness and strength properties are largely similar to those of their non-spliced counterparts. The performance characteristics obtained from the detailed test measurements are used within the discussions to highlight issues relevant for application in practice.

Journal article

Bompa DV, Elghazouli AY, 2019, Inelastic cyclic behaviour of RC members incorporating threaded reinforcement couplers, Engineering Structures, Vol: 180, Pages: 468-483, ISSN: 0141-0296

This paper describes an experimental investigation into the inelastic cyclic performance of reinforced concrete members incorporating mechanical reinforcement splices. Based on a survey of available mechanical splicing forms, two types of threaded couplers with different geometric configurations, namely ‘parallel threaded couplers’ and ‘parallel threaded sleeve couplers’ are selected for detailed experimental assessment. The fundamental uniaxial monotonic and cyclic response of reinforcement bars connected with threaded mechanical splices is firstly examined through bare (in-air) and embedded (in-concrete) tests, and their response is compared with that of their non-spliced counterparts. This is followed by an experimental study on four large scale reinforced concrete specimens subjected to lateral inelastic cyclic displacements, which provides a direct comparison between the performance of members with or without the two types of reinforcement couplers as well with or without a co-existing axial load. The test results enable a direct comparative assessment of the key response characteristics of the specimens including stiffness, strength, ductility and energy dissipation. Overall, the results show that members incorporating reinforcement bars connected through threaded mechanical couplers can provide considerable ductility and energy dissipation. However, the coupler-concrete interaction behaviour, which depends primarily on the geometry and location of the threaded coupler, has a significant influence on the inelastic cyclic response and ductility levels exhibited by reinforced concrete members. The experimental results indicate that the presence of the slender coupler alters the plastic hinge behaviour by localising the curvatures between the coupler and interface, reducing the rotational capacity. In contrast, the response of members with compact couplers, and without axial load, is virtually identical to that of the specimen with continu

Journal article

Bompa DV, Elghazouli AY, 2018, Response of reinforced rubberised concrete members under combined loading conditions, Publisher: Imperial College London

Report

Bompa DV, Elghazouli AY, 2018, Monotonic and cyclic performance of threaded reinforcement splices, Structures, Vol: 16, Pages: 358-372, ISSN: 2352-0124

This paper examines the fundamental uniaxial monotonic and cyclic response of reinforcement bars connected with threaded mechanical couplers. Based on a survey of available splicing forms, two types of threaded couplers with different geometric configurations, namely ‘parallel threaded couplers’ and ‘parallel threaded sleeve couplers’ are selected for detailed assessment. An experimental study consisting of twenty-four bare (in-air) and embedded (in-concrete) specimens incorporating threaded couplers and non-spliced counterparts, is described. The results enable direct assessment of strength as well as complete deformation characteristics, including the post-cracking and post-yield response, for both monotonic and cyclic conditions. After describing the material properties and specimen details, the main observations are reported based on detailed measurements of crack kinematics including crack width and spacing through a digital image correlation system. Complementary numerical studies, undertaken using nonlinear finite element procedures which are validated against the tests, enabled supplementary parametric investigations accounting for wider ranges of coupler geometries. The findings show that existing guidelines may be used for assessing the crack width and spacing, by accounting for the characteristic bond behaviour at the rebar and coupler regions. The complete deformational response may be obtained by using a suggested stiffness reduction factor that depends on the coupler geometry. Several ‘in-air’ performance parameters may also be used as a basis for the selection and implementation of couplers in applications requiring ductile member behaviour.

Journal article

Bompa DV, Elghazouli A, 2018, Response of Steel Reinforcement Incorporating Threaded Mechanical Couplers at Elevated Temperatures, Response of Steel Reinforcement Incorporating Threaded Mechanical Couplers at Elevated Temperatures, Publisher: Imperial College London

Report

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