Browsing by Author "Sahmaran, M"

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    Performance of engineered cementitious composites under drop-weight impact: Effect of different mixture parameters
    Yildirim, G; Khiavi, FE; Anil, Ö; Sahin, O; Sahmaran, M; Erdem, RT
    Current research focuses on the experimental and numerical determination of impact performance of engineered cementitious composites (ECC). Performance assessment of ECC beams with different mixture parameters was made. Mixtures were produced with different replacement rates of Class-F fly ash and slag with Portland cement, water to binder ratios and fiber types (polyvinyl alcohol [PVA] and nylon [N]). Experimental works were validated with incremental dynamic analyses performed by ABAQUS finite element software. Impact testing results were further supported by mechanical property results. Results reveal that each individual mixture parameter used is distinctively effective in modifying the properties under both sudden impact and slow static loading. In brief, enhanced impact resistance is noted when ECC is produced with slag, low amounts of pozzolanic materials, low W/B ratio, fiber addition and PVA fibers. Experimental results were also in line with the numerical results from ABAQUS largely. Significantly, cost-effective N fibers were also shown to be fully replaceable with costly PVA fibers without jeopardizing mechanical/impact performance, if mixture design parameters are adjusted suitably. Current research is likely to attract further research on the development of ECC that is with lower cost and comparable impact/mechanical performance with regards to widely studied more expensive counterparts in the literature.
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    Impact behaviour of nanomodified deflection-hardening fibre-reinforced concretes
    Demirhan, S; Yildirim, G; Banyhussan, QS; Koca, K; Anil, O; Erdem, RT; Sahmaran, M
    The behaviour of concrete under sudden impact loads is complex. Moreover, very little is known about the impact behaviour of high-performance fibre-reinforced concretes (HPFRCs). To account for this, nanomodified deflection-hardening HPFRC mixtures incorporating coarse aggregates were produced with three ratios of fly ash to Portland cement (0.0, 0.2 and 0.4), three nanomaterials (nanosilica, nano-alumina and nanocalcite) and two hybridised fibre combinations (hooked-end steel with polyvinyl alcohol, or hooked-end steel with brass-coated microsteel) and tested for basic mechanical properties and flexural impact resistance. After experimental testing, beams used in impact testing were modelled using Abaqus. Cubic compressive strength did not change significantly with the differences in mixture parameters, although this was not the case for flexural parameters. For a given fly ash/Portland cement ratio and nanomaterial type, mixtures with hooked-end steel and polyvinyl alcohol fibres exhibited higher displacement and lower flexural strength capacity than those with hooked-end steel and brass-coated microsteel fibres. Nano-alumina contributed best to the development of mechanical properties and impact resistance of HPFRCs, followed by nanosilica and nanocalcite. Results validate the idea that costly polyvinyl alcohol fibres can be fully replaced with brass-coated microsteel fibres without risking mechanical properties and impact resistance, as long as matrix properties are properly controlled.
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    Impact resistance of deflection-hardening fiber reinforced concretes with different mixture parameters
    Banyhussan, QS; Yildirim, G; Anil, Ö; Erdem, RT; Ashour, A; Sahmaran, M
    The impact behavior of deflection-hardening High Performance Fiber Reinforced Cementitious Concretes (HPFRCs) was evaluated herein. During the preparation of HPFRCs, fiber type and amount, fly ash to Portland cement ratio and aggregate to binder ratio were taken into consideration. HPFRC beams were tested for impact resistance using free-fall drop-weight test. Acceleration, displacement, and impact load versus time graphs were constructed and their relationship to the proposed mixture parameters were evaluated. The paper also aims to present and verify a nonlinear finite element analysis, employing the incremental nonlinear dynamic analysis, concrete damage plasticity model, and contact surface between the dropped hammer and test specimen available in ABAQUS. The proposed modeling provides extensive and accurate data on structural behavior, including acceleration, displacement profiles, and residual displacement results. Experimental results which are further confirmed by numerical studies show that impact resistance of HPFRC mixtures can be significantly improved by a proper mixture proportioning. In the presence of high amounts of coarse aggregates, fly ash, and increased volume of hybrid fibers, impact resistance of fiberless reference specimens can be modified in a way to exhibit relatively smaller displacement results after impact loading without risking the basic mechanical properties and deflection-hardening response with multiple cracking.