Dan Bompa
University of Surrey, Civil and Environmental Engineering, Faculty Member
This paper studies the response of unreinforced masonry (URM) members made of hydraulic lime mortar and fired clay bricks, commonly found in heritage structures, strengthened with textile reinforced mortar (TRM) overlays. The... more
This paper studies the response of unreinforced masonry (URM) members made of hydraulic lime mortar and fired clay bricks, commonly found in heritage structures, strengthened with textile reinforced mortar (TRM) overlays. The investigation includes URM and TRM-strengthened diagonal compression tests on square panels, and relatively large-scale wall specimens subjected to combined gravity and lateral cyclic loads. Complementary compression, tension, and interface material tests are also carried out. The diagonal panel tests show that the TRM effectiveness depends in a non-proportional manner on the overlays, render thickness, and substrate strength. The enhancement in stiffness, strength, and ultimate shear strain, using one to four mesh layers on each side, is shown to vary in the range of 49–132%, 102–536%, and 300–556% respectively. It is shown that strut crushing typically governs the response of such low-strength URM masonry elements confined by TRM overlays. The cyclic tests on...
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This paper presents an experimental study into the fundamental response of reinforced concrete members, which incorporate rubber particles obtained from recycled tyres, subjected to combined axial–bending loading conditions. Tests on... more
This paper presents an experimental study into the fundamental response of reinforced concrete members, which incorporate 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 fibre-reinforced polymer (FRP) sheets are described. The results show that the rubber particles enhance the confinement level activated, with confined/unconfined strength and deformation capacity ratios at least twice 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 with FRP-confined members. The external confinement substantially enhanced 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 e...
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This paper presents a focused comparative case study considering the influence of natural and synthetic fibers on the fresh and mechanical properties of concrete. Locally sourced 19 mm long sisal fibers from sisalana leaves and... more
This paper presents a focused comparative case study considering the influence of natural and synthetic fibers on the fresh and mechanical properties of concrete. Locally sourced 19 mm long sisal fibers from sisalana leaves and manufactured polypropylene fibers were incorporated in a normal strength concrete matrix with fiber volumetric contents of 1%. After describing the measured aggregate characteristics, mix designs, and fresh concrete properties, several destructive and non-destructive tests on hardened concrete were undertaken. The former included compression tests on cylinders and flexural tests on prismatic samples, and the latter included ultrasonic pulse velocity and rebound number tests. The workability of sisal-fiber reinforced concrete was generally lower than the nominal concrete and that provided with polypropylene fibers by about 20%, largely due to the hydrophilic nature of the natural fibers. Test results showed that the presence of sisal fibers can improve the com...
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This paper investigates the structural performance of cruciform shear-head systems fully integrated in RC flat slabs at interior connections to steel columns. The test results from a series of six large scale members of which two were... more
This paper investigates the structural performance of cruciform shear-head systems fully integrated in RC flat slabs at interior connections to steel columns. The test results from a series of six large scale members of which two were provided with headed shear studs, offer a direct evaluation of the full load-deformation behaviour of the specimens as well as the ultimate punching shear strength attained prior to failure at the critical slab perimeter outside the shear-head region. Particular focus is given to the influence of the shear-head and headed shear stud reinforcement to the member kinematics and failure characteristics. The experimental findings coupled with shear field analyses enable the development of analytical models that depict the rotational response and flexural strength as a function of the shear-head characteristics, and support the definition of a shear-head dependent control perimeter required for punching shear strength assessments. Additionally, analytical design expressions that adopt the fundamentals of Model Code 2010, which account for the characteristics of the shear-head system, are proposed and their results capture in a more realistic manner the shear-head influence on the punching shear strength of RC flat slabs in such hybrid configurations in comparison with strength predictions from current conventional RC design methods.
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This study describes experimental and numerical investigations into the inelastic behaviour of hybrid reinforced concrete (RC) beams. The RC beams are connected to steel columns by means of fully embedded structural steel profiles.... more
This study describes experimental and numerical investigations into the inelastic behaviour of hybrid reinforced concrete (RC) beams. The RC beams are connected to steel columns by means of fully embedded structural steel profiles. Observations from a series of ten full-scale hybrid Steel/RC specimens are presented. Nonlinear finite element procedures are carried out and validated against the experimental results from the hybrid tests in this paper. The ability of the numerical models to provide faithful prediction, using a consistent set of material modelling parameters, provides a high level of confidence in the reliability of the simulation techniques. Finally, some simplified analytical representations of the failure surfaces are proposed in which potential failure conditions are predicted and classified in reference to a suggested hybrid Mode Index.
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Research Interests: Earthquake, Seismic, Analytical, Numerical, Connection, and 3 moreExperimental, Joint, and Prequalification
ECC
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Abstract Interest in geopolymer concrete (GeoPC) and in rubberised concrete (RuC) has grown over the past two decades. The former offers an attractive alternative to ordinary Portland cement (OPC) concrete given its environmental... more
Abstract Interest in geopolymer concrete (GeoPC) and in rubberised concrete (RuC) has grown over the past two decades. The former offers an attractive alternative to ordinary Portland cement (OPC) concrete given its environmental footprint, while the latter provides a sustainable solution to tyre recycling and helps mitigate the depletion of natural aggregates. The benefits of combining the merits of GeoPC and RuC to form rubberised geopolymer concrete (RuG) as a potential sustainable construction material have been recognised in the past few years. As such, this paper presents a detailed review of RuG highlighting its constituent components, preparation and curing aspects, fresh and physical qualities, durability features, and thermal and sound insulation qualities, with a particular focus on mechanical properties. The influence of crumb rubber replacement on key characteristics is critically reviewed, including the effect of binder type, alkaline solution, alkaline solution-to-binder content, and curing conditions. Comparative quantitative assessments and prediction relationships are also presented where relevant. Finally, gaps in the available literature and recommendations for future research are outlined, with a view to supporting further developments in research and future deployment of RuG materials in practice. Whilst previous studies demonstrate the significant potential of RuG and provide essential information on its fundamental properties, this review reveals that much research is still needed in order to optimise the merits of the material and to provide a full characterisation of its behaviour at both the material and structural levels under various loading conditions.
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Abstract 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... more
Abstract 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.
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Research Interests: Engineering, Chemical Engineering, Civil Engineering, Materials Science, Technology, and 15 moreStructural Engineering, Behavior, Digital Image Correlation, Strength, Stiffness, Deformation, Reinforcement, Elevated Temperatures, Fire safety, Science Technology, Maritime Engineering, Structural Performance, Bars, Steel Reinforcement, and Engineering Civil
Research Interests: Engineering, Materials Science, Behavior, Prediction, Finite element method, and 15 moreDigital Image Correlation, Steel, Stiffness, Reinforcement, Science Technology, Cyclic Response, COLUMNS, Parametric Statistics, Bars, SLIP, Seismic Performance, Engineering Civil, Bond Stress, Rebar, and inelastic behaviour
Research Interests: Engineering, Civil Engineering, Materials Science, Technology, Structural Engineering, and 15 moreFinite element method, Numerical Modelling, Finite Element Analysis, Resistance, Strength, Reinforcement, Embedment, Column, Science Technology, Punching Shear, Parametric Statistics, Coefficient, Engineering Civil, Connections, and concrete slabs
Research Interests: Engineering, Civil Engineering, Materials Science, Technology, Structural Engineering, and 15 moreBehavior, Geometry, Building Construction, Building, Strength, Composite Material, Bond Strength, Bond, Science Technology, Cover, Crumb Rubber, Engineering Civil, Rubberised concrete, Deformed Bars, and recycled rubber
Research Interests: Engineering, Civil Engineering, Materials Science, Technology, Elasticity, and 14 moreBuilding Construction, Natural rubber, Building, Strength, Particles, Composite Material, Building and Construction Materials, Science Technology, Modulus, Constitutive Equation, Crumb Rubber, Building Construction Technology and Management, Engineering Civil, and Clamping
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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... more
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 cor...
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This paper examines the performance of multi-binder conventional geopolymer mixes (GCMs) with relatively high early strength, achieved through curing at ambient temperature. Mixes incorporating ground granulated blast-furnace slag (GGBS),... more
This paper examines the performance of multi-binder conventional geopolymer mixes (GCMs) with relatively high early strength, achieved through curing at ambient temperature. Mixes incorporating ground granulated blast-furnace slag (GGBS), fly ash (FA) and microsilica (MS) and sodium metasilicate anhydrous, were assessed in terms of workability, mechanical properties and embodied carbon. A cement mortar was also prepared for the sake of comparison. The best performing GCM was then used as a reference for rubberised geopolymer mixes (RuGM) in which the mineral aggregates were replaced by recycled rubber particles in proportions up to 30% by volume. Experimental results were combined with embodied carbon estimations in a multi-criteria assessment to evaluate the performance of each material. A mix with a 75/25 GGBS-to-FA ratio, in which 5% MS was added, had the best performance in terms of strength, workability, water absorption and environmental impact. The compressive strength was ab...
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This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications. The environmental influence of cement content, aggregate production,... more
This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications. The environmental influence of cement content, aggregate production, transportation, and waste landfilling is analysed by undertaking a life cycle assessment and considering a life cycle inventory largely specific for the region. To obtain a detailed insight into the optimum life cycle parameters, a sensitivity study is carried out in which supplementary cementitious materials, different values of natural-to-recycled aggregate content ratio and case-specific transportation distances were considered. The results show that carbon emissions were between 323 and 332 kgCO 2 e per cubic metre of cement only natural aggregate concrete. These values can be reduced by up to 17% by replacing 25% of the cement with fly ash. By contrast, carbon emissions can increase when natural coarse aggregates are replaced by recycled aggregates in...
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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... more
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 m...
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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... more
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 avai...
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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... more
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 sy...