Publications
388 results found
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
Bompa DV, Elghazouli AY, 2019, Properties of hydraulic lime mortars subjected to dry-wet cycles, Publisher: Imperial College London
Bompa DV, Elghazouli AY, 2019, Seismic behaviour and design of steel reduced beam section connections, SECED 2019 Conference
Pilakoutas K, Papastergiou P, Hu H, et 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
Bompa D, Elghazouli A, 2019, Seismic Behaviour and Design of Steel Reduced Beam Section Connections, SECED2019 Earthquake Risk and Engineering Towards a Resilient World
Liapopoulou M, Bravo-Haro M, Elghazouli A, 2019, Ultimate Seismic Performance of Degrading Structures, SECED2019 Earthquake Risk and Engineering Towards a Resilient World
Liapopoulou M, Bravo-Haro M, Elghazouli A, 2019, Design Collapse Capacity Spectra for Ductile Systems, SECED2019 Earthquake Risk and Engineering Towards a Resilient World
Bravo-Haro M, Elghazouli A, 2019, Open-Source Low-Cost Sensors for Vibration Monitoring, SECED2019, Earthquake Risk and Engineering Towards a Resilient World
Cedron F, Elghazouli A, 2019, Seismic Performance of Cylindrical Lattice Shells, SECED2019 Earthquake Risk and Engineering Towards a Resilient World
Sahin B, Bravo-Haro M, Elghazouli A, 2019, Cyclic Deterioration Modelling for Composite Steel-ConcreteMembers, SECED2019 Earthquake Risk and Engineering Towards a Resilient World
Bogdan T, Bompa DV, Elghazouli AY, et 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.
Li Z, Huo J, Liu Y, et al., 2019, Experimental study on normal and post-fire RC connections with different detailing techniques subjected to column removal, PROTECT2019 International Conference on Performance, Protection and Strengthening of Structures under Extreme Loading and Events
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.
Bompa DV, Elghazouli AY, 2019, Axial-bending interaction of high deformability FRP-confined circular concrete members, ACIC 2019 Advanced Composites in Construction
Li Z, Liu Y, Huo J, et al., 2019, Experimental and analytical assessment of RC joints with varying reinforcement detailing under push-down loading before and after fires, Engineering Structures, Vol: 189, Pages: 550-564, ISSN: 0141-0296
This paper examines the behaviour of RC beam-column joints with different reinforcement detailing arrangements under pushdown loading before and after fires. The thermal responses of the RC joint specimens are firstly described, including the development of the temperature fields and the horizontal reactions as well as the deflections during the heating and cooling phases. Subsequently, displacement-controlled push-down tests are performed, and the vertical load, horizontal reactions as well as detailed deformations are monitored. The bending moment-rotation relationships are derived from the test results, together with an account of the observed failure modes. The mechanical behaviour is also discussed in detail, including the rotational capacity, with emphasis on the effect of different reinforcement detailing arrangements as well as the post-fire condition. Particular attention is given to comparing the experimental axial-moment strength interaction curves and theoretical predictions under ambient conditions so as to examine the underlying mechanisms. In order to support practical application, a simplified analytical method is proposed for simulating the push-down response, based on the combined loading states and idealised constitutive relations, taking into consideration the restraint effect due to horizontal restraint or fire conditions. The suggested analytical procedure is shown to be a reliable and effective approach for representing the behaviour. Based on the findings of this investigation, practical considerations for enhancing the rotational capacity of RC joints are highlighted.
Bompa D, Elghazouli A, 2019, Axial-bending Interaction of High Deformability FRP-confined CircularConcrete Members, International Conference on Advanced Composites in Construction
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.
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.
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
Bompa DV, Elghazouli AY, 2018, Response of reinforced rubberised concrete members under combined loading conditions, Publisher: Imperial College London
Bravo-Haro M, Elghazouli A, 2018, Influence of earthquake duration on the response of steel moment frames, Soil Dynamics and Earthquake Engineering, Vol: 115, Pages: 634-651, ISSN: 0267-7261
The influence of ground motion duration on the seismic response of steel moment frames is examined is this paper, with due consideration for cyclic degradation effects. A set of 77 spectrally equivalent pairs of short and long records is utilised in detailed nonlinear dynamic assessments in order to isolate the effects of ground motion duration. The influence of duration is firstly evaluated considering degrading and non-degrading idealised bilinear SDOF systems, for various levels of lateral strength representing practical ranges encountered in design. Subsequently, a sensitivity assessment focusing on the main parameters affecting the response of hysteretic degrading models is carried out through comparative incremental dynamic analysis. Whilst the effect of duration becomes more pronounced with the increase in lateral strength demands, particularly when approaching collapse, the cyclic degradation rate is shown to play a significant role even at lower levels typically associated with design. The performance of EC8-compliant frames indicates a higher probability of collapse when long-duration ground motion records are used, with a typical reduction of about 20% in the collapse capacity, in comparison with short-duration cases. The influence of duration is also examined through collapse capacity spectra, based on the seismic performance of 50 steel moment frames, which show that considerable reduction in the structural collapse capacity of structural systems occurs when relatively long duration records are adopted, for a wide range of dynamic characteristics. This becomes particularly evident in the case of buildings with relatively significant cyclic deterioration rates, where collapse capacity reductions up to 40% due to the influence of earthquake duration are obtained.
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.
Bravo-Haro M, Elghazouli AY, 2018, Permanent seismic drifts in steel moment frames, Journal of Constructional Steel Research, Vol: 148, Pages: 589-610, ISSN: 0143-974X
This paper examines residual drift demands in steel moment-resisting frames incorporating the influence of degradation and ground motion frequency content. Detailed assessments are carried out using 54 multi-storey framed buildings, with a wide range of structural characteristics, which are designed according to the provisions of Eurocode 8. In order to identify the influence of cyclic and in-cycle degradation effects, the analysis is carried out with and without degradation modelling. Incremental dynamic analysis is employed in order to achieve various limits of lateral strength demand, using a suite of 56 ground motion records. It is shown that residual drifts are markedly higher in degrading models in comparison with non-degrading models, with the differences being more pronounced in relatively short period ranges, when higher rates of cyclic deterioration are employed, and for comparatively high lateral strength demand levels. The residual drift demand is also shown to increase with the increase in number of stories, and is often concentrated in the lower levels when degrading models are used. Overall, significant residual drift demands are observed in the structural systems considered, with a high likelihood of exceeding a 0.5% residual drift limit in most cases. Based on the results, two simplified prediction relationships are proposed to estimate the permanent drifts of multi-storey steel moment framed systems. The first is concerned with the design stage based on the results of elastic analysis, whilst the second is associated with post-earthquake structural assessment based on actual measurements of residual drifts.
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
Li Z, Liu Y, Huo J, et al., 2018, Experimental assessment of fire-exposed RC beam-column connections withvarying reinforcement development lengths subjected to column removal, Fire Safety Journal, Vol: 99, Pages: 38-48, ISSN: 0379-7112
This paper describes an experimental investigation into the behaviour of RC beam-column connections under a column removal scenario induced by fire. A purpose-built hybrid heating furnace is employed to carry out the fire tests on five RC connections with varying reinforcement development lengths, with and without cooling effects. The thermal response of the RC connection specimens, including the temperature field and the axial force-furnace temperature curves, is firstly described. Subsequently, push-down tests are carried out on the beam-column connections, and the horizontal support reactions are closely monitored using a specially-designed sensor system. Based on the experimental results, the joint vertical load-displacement and bending moment-rotation relationships are presented, together with an account of the failure modes observed. The mechanical behaviour is discussed in detail, including the tying and rotation capacity provided by the connection specimens, with emphasis on the effect of the reinforcement development length as well as the heating regime. The experimental capacity interaction curves are also compared with the theoretical prediction for ambient condition, and employed to carry out a detailed examination of the underlying failure mechanisms. Finally, the findings are used to provide practical recommendations for enhancing the structural robustness of structural configurations of the form considered in this study.
Elghazouli AY, Bompa DV, Xu B, et al., 2018, Performance of rubberised reinforced concrete members under cyclicloading, Engineering Structures, Vol: 166, Pages: 526-545, ISSN: 0141-0296
This paper presents an experimental investigation into the cyclic behaviour of reinforced concrete members incorporating a significant proportion of recycled rubber particles as a replacement for mineral aggregates. Tests were carried out on thirteen large scale members of circular cross-section, with and without external confinement, and with different proportions of rubber content and axial loads. The specimens were subjected to inelastic lateral cyclic displacements and predefined levels of co-existing axial loading. After describing the testing arrangement and specimen details, the main results and observations are provided and discussed. The test results enable a direct comparative assessment of the key response characteristics of the specimens, with focus on stiffness properties and strength interaction, as well as ductility and energy dissipation. It is shown that rubberised reinforced concrete members can offer a good balance between bending capacity and ductility in comparison with conventional reinforced concrete members, particularly for low levels of axial loads. In the presence of relatively high axial loading and when a significant proportion of rubber content is used, external confinement such as through FRP sheets as employed in this study, can be adopted to recover the required capacity and to provide highly stable hysteretic response. The implications of the findings on the use of rubberised reinforced concrete members in practice, and procedures that can be used to determine the main design parameters, are also highlighted within the discussions.
Bravo-Haro MA, Tsitos A, Elghazouli AY, 2018, Drift and rotation demands in steel frames incorporating degradation effects, Bulletin of Earthquake Engineering, Vol: 16, Pages: 4919-4950, ISSN: 1570-761X
This paper is concerned with the assessment of seismic drift demands in steel moment frames designed to comply with Eurocode 8 provisions, with due account for cyclic and in-cycle degradation. In addition to degradation effects, the main parameters examined include the ground motion frequency content as well as the level of constant relative strength or inelasticity. To represent a wide range of structural characteristics, a set of 54 multi-storey frames are considered, in which the number of stories, steel profiles, seismic hazard and compliance criteria are varied. Detailed incremental dynamic analyses are performed on the full set of frames using a suite of 56 far-field ground motion records, which are scaled appropriately to achieve different levels of inelastic demand or equivalent behaviour factors. The seismic performance is evaluated in terms of maximum global and local drifts as well as beam chord rotations. Characteristic results show that maximum response in terms of global deformations and inter-storey drifts is significantly affected by degradation phenomena, along with the ground motion frequency content and the level of inelastic demand. For medium rise typologies subjected to earthquakes with relatively high frequency content, concentration of seismic demand in terms of inter-storey drift is captured by the degrading models and leads to early development of plastic mechanisms. The seismic demand scenarios used in this study, through spectral acceleration-based scaling of ground motions, indicate that the influence of degradation can be significant not only at collapse levels but also at those associated with typical design situations. Finally, based on the extensive analyses carried out in this investigation, expressions for predicting the global and local demands are proposed and discussed.
Ho HC, Liu X, Chung KF, et al., 2018, Hysteretic behaviour of high strength S690 steel materials under low cycle high strain tests, Engineering Structures, Vol: 165, Pages: 222-236, ISSN: 0141-0296
This paper describes a detailed experimental investigation into structural behaviour of S690 steel materials under both monotonic and cyclic loading conditions. In addition to 6 monotonic tensile tests, which were conducted to establish basic mechanical properties, 36 cyclic tests were then carried out in order to examine hysteretic behaviour of the S690 steel materials under various target strains and loading frequencies. The experimental arrangements used for the monotonic and the cyclic tests are described, and a detailed account of the test results is provided. The monotonic tests showed that all the S690 steel specimens satisfied the ductility requirements stipulated in current European provisions which are typically based solely on monotonic behaviour. In the cyclic tests, most specimens were able to complete 20 cycles with target strain amplitudes of ±2.5%, ±5.0%, ±7.5%, and ±10.0%, under loading frequencies of 0.1, 0.5, 1.0 and 2.0 Hz. However, some specimens fractured at the 20th cycle when the target strains were ±10.0% irrespective of the loading frequency. Additionally, significant strength enhancement due to strain hardening was observed and quantified in the cyclic tests, depending on the level of target strains. The results additionally illustrated the importance of using actual instantaneous cross-sectional diameters for evaluating true stresses in order to obtain actual representative hysteretic curves.In general, the study highlights the importance of establishing seismic ductility requirements based on cyclic tests, particularly for high strength steel materials. It also provides a detailed assessment of the hysteretic characteristics, which can be directly employed to develop reliable constitutive models for high strength S690 steel materials under seismic loading conditions.
Bompa DV, Elghazouli AY, 2018, Ductility of Reinforced Concrete Members Incorporating Mechanical Splices, 16th European Conference on Earthquake Engineering (16ECEE)
Bravo-Haro M, Elghazouli AY, 2018, INFLUENCE OF GROUND MOTION DURATION ON THE SEISMIC RESPONSE OF STEEL MOMENT FRAMES, 16th European Conference on Earthquake Engineering (16ECEE)
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