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    Application of waste ceramic powder as a cement replacement in reinforced concrete beams toward sustainable usage in construction
    (Elsevier, 2023) Aksoylu, Ceyhun; Oztilic, Yasin Onuralp; Bahrami, Alireza; Yildizel, Sadik Alper; Hakeem, Ibrahim Y.; Ozdoner, Nebi; Basaran, Bogachan
    The main purpose of this study was to investigate the flexural behavior of reinforced concrete beams (RCBs) containing waste ceramic powder (CP) as partial replacement of cement. For this purpose, flexural tests were carried out using various amounts of mixing ratios. By determining the amount of CP utilized in the optimum ratios, it was aimed both to make predictions for design engineers and to show its beneficial effect on the environment by recycling the waste material. For this purpose, twelve specimens were produced and verified to monitor the flexural behavior. The longitudinal reinforcements percentage (0.77%, 1.21%, and 1.74%) and CP percentage (0%, 10%, 20%, and 30%) were chosen as the parameters. CP could be effectively used up to 10% of cement as a replacement material. Increasing the CP percentage by more than 10% could considerably reduce the load-carrying capacity, ductility, and stiffness of RCBs, specifically when the longitudinal reinforcements percentage was high. In other words, as CP increased from 0% to 30%, the load-carrying capacity decreased between 0.4% and 27.5% compared with RCBs with the longitudinal tension reinforcements of 2 phi 8 without CP. However, reductions of 5.5-39.8% and 2.15-39.5% in the load-carrying capacity occurred respectively compared with RCBs with the longitudinal tension reinforcements of 2 phi 10 and 2 phi 12 without CP. The achieved longitudinal reinforcements percentage was close to the balanced ratio, while more than 10% CP cannot be used without any precautions for mixtures.
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    Behavior of CFRP-strengthened RC beams with circular web openings in shear zones: Numerical study
    (Elsevier Science Inc, 2022) Ozkilic, Yasin Onuralp; Aksoylu, Ceyhun; Yazman, Sakir; Gemi, Lokman; Arslan, Musa Hakan
    In practice, especially the basement floor beams are drilled and damaged by the users. In some cases, this damage to the beams can be significant for the load-bearing element and the whole structure. In this study, the behavior of reinforced concrete beams with circular openings and the failure types resulting from strengthening these beams with CFRP are parametrically investigated. The diameter of the opening/beam height ratio (D/H), con-crete compressive strength, stirrup spacing, the position of the opening to the beam support, the type of CFRP application, CFRP ply orientation, and the number of CFRP layers were selected as parameters. Numerical models were verified using 9 specimens having different circular openings with/without CFRP strengthening and the analyses of 95 numerical models with the selected parameters were carried out utilizing the finite element program, ABAQUS. The ultimate load capacity, ductility, stiffness, energy dissipation capacity and failure modes of the beams were determined. As a result of the study, it was observed that there was no significant loss in ductility for the beams with D/H < 0.3 and the number of CFRP layer and type of application did not have a significant effect on D/H < 0.44. However, for the beams with D/H > 0.64, the CFRP application that completely surrounds openings should be preferred instead of partial CFRP strengthening. In addition, the concrete strength is an effective parameter for the beams with D/H < 0.44. The effect of the stirrup spacings in the beam on the ductile behavior was also limited with the increase in the hole diameter. The number of CFRP layers should theoretically be 4 for an effective strengthening in beams with D/H > 0.44. Finally, U wrapping is recommended instead of using full wrapping. It has been seen that the location and diameter of the hole are very important parameters in the failure type of the beam.
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    Bending performance of dapped-end beams having web opening: Experimental and numerical investigation
    (Elsevier, 2023) Aksoylu, Ceyhun; Özkılıç, Yasin Onuralp; Çeledir, Emrullah; Arslan, Musa Hakan
    Reinforced concrete dapped-end (purlin) beams are frequently used in prefabricated industrial structures. The main task of these beams is to safely carry the loads on the roof. Considering the number of these purlin beams in industrial buildings, it is extremely important for manufacturers to product these beams with less concrete without reducing the load carrying capacity. Since these purlin beams are under the effect of bending and shear forces, controlled creating openings in beam span can have significant economic benefits for the manufacturer. Therefore especially economic design perspective, it is so crucial to determine the amount of openings that will not cause a significant change in the bending behavior. In this study, the behavior of dapped-end purlins with openings was experimentally and numerically investigated. In the experimental step, seven purlin beams having different opening configurations were tested under four-point loading to investigate the openings effects on beam structural behavior. In this step opening length to total length varying between 0.075 and 0.325 was selected as a main parameter. After test, the numerical models were created and verified using experimental findings. After this step, in the parametric study part of the paper, the effects of shear span, depth of the opening and length of opening and different opening configurations (such as segmentation) which were not tested in experiments, were examined. The experimental outcomes revealed that increases in the opening did not provide a significant effect on the load capacity. This can be explained by the fact that the openings are in the bending region. The numerical findings showed that increasing shear span to depth ratio (av/d) ratio did not change rigidity but decreased the load capacity. However, no effect was observed on the opening height provided that it is at least as far away from the upper and lower longitudinal reinforcements bars as the concrete-cover margin. On the other hand, increasing opening/purlin length (especially higher than 0.375) reduces the capacity. However, segmented openings (multiple openings instead of single whole openings) did not reduce capacity even if total opening/ purlin length was 0.525.
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    Buckling Analysis of CNT-Reinforced Polymer Composite Beam Using Experimental and Analytical Methods
    (Mdpi, 2023) Madenci, Emrah; Ozkilic, Yasin Onuralp; Aksoylu, Ceyhun; Asyraf, Muhammad Rizal Muhammad; Syamsir, Agusril; Supian, Abu Bakar Mohd; Mamaev, Nicolay
    The aim of this article was to investigate the effect of carbon nanotubes (CNTs) on the buckling behavior of fiber-reinforced polymer (FRP) composites. The materials used included three layers: carbon-fiber-reinforced polymer (CFRP), epoxy and CNTs. A set of mechanical tests, such as compression and buckling tests, was performed, and also analytical solutions were developed. Damage analysis was also carried out by controlling the damage initiation and crack progression on the composite samples. Experimental results revealed that using 0.3% with CNT additives enhanced the buckling performance of the composite. Finally, the average load-carrying capacity for the clamped-clamped boundary condition was 268% higher in the CNT samples and 282% higher in the NEAT samples compared to the simple-simple condition.
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    Compressive Behavior of Pultruded GFRP Boxes with Concentric Openings Strengthened by Different Composite Wrappings
    (Mdpi, 2022) Aksoylu, Ceyhun; Ozkilic, Yasin Onuralp; Madenci, Emrah; Safonov, Alexander
    Web openings often need to be created in structural elements for the passage of utility ducts and/or pipes. Such web openings reduce the cross-sectional area of the structural element in the affected region, leading to a decrease in its load-carrying capacity and stiffness. This paper experimentally studies the effect of web openings on the response of pultruded fiber-reinforced polymer (PFRP) composite profiles under compressive loads. A number of specimens have been processed to examine the behavior of PFRP profiles strengthened with one or more web openings. The effects of the size of the web opening and the FRP-strengthening scheme on the structural performance of PFRP profiles with FRP-strengthened web openings have been thoroughly analyzed and discussed. The decrease in load-carrying capacity of un-strengthened specimens varies between 7.9% and 66.4%, depending on the diameter of the web holes. It is observed that the diameter of the hole and the type of CFRP- or GFRP-strengthening method applied are very important parameters. All CFRP- and GFRP-strengthening alternatives were successful in the PFRP profiles, with diameter-to-width (D/W) ratios between 0.29 and 0.68. In addition, the load-carrying capacity after reinforcements made with CFRP and GFRP increased by 3.1-30.2% and 1.7-19.7%, respectively. Therefore, the pultruded profiles with openings are able to compensate for the reduction in load-carrying capacity due to holes, up to a D/W ratio of 0.32. The capacity significantly drops after a D/W ratio of 0.32. Moreover, the pultruded profile with CFRP wrapping is more likely to improve the load-carrying capacity compared to other wrappings. As a result, CFRP are recommended as preferred composite materials for strengthening alternatives.
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    Crashworthiness performance of filament wound GFRP composite pipes depending on winding angle and number of layers
    (Elsevier, 2024) Hakeem, Ibrahim Y.; Ozkilic, Yasin Onuralp; Bahrami, Alireza; Aksoylu, Ceyhun; Madenci, Emrah; Asyraf, Muhammad Rizal Muhammad; Beskopylny, Alexey N.
    The main goal of this study is to enhance the crashworthiness performance of tubular composites to absorb more energy by optimizing the winding angle of their fibers. The crashworthiness performance of glass fiber-reinforced polymer composite pipes manufactured using the filament winding is investigated in detail. The effects of the winding angle of the fibers and thickness of the tube wall on the energy absorption were examined through quasi-static compression tests. The composite pipes were produced with 1200 tex E-glass fibers and Epikote 828 resin as the matrix material. The winding angles of +/- 30 degrees, +/- 45 degrees, +/- 55 degrees, +/- 75 degrees, and +/- 90 degrees were evaluated, and the number of the winding layers, ranged from 1 to 3, was also assessed. Quasi-static axial compressive loading was applied to 15 specimens using a hydraulic actuator. The results revealed that the one-layer specimens experienced buckling damage at low load levels, while an increase in the number of the layers led to higher load-carrying capacity and different types of damages. Furthermore, as the number of the layers increased, the load-carrying capacity and energy absorption of the specimens significantly improved. Progressive failure was observed in the specimens [+/- 90] for all the layers' configurations, with the specimen [+/- 90]3, having three layers, exhibiting the highest performance in terms of the load-carrying capacity and energy absorption. The failure modes indicated a combination of the fibers' separation, buckling, diagonal shear failure, and crushing in the upper and lower heads.
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    Creep Properties and Analysis of Cross Arms' Materials and Structures in Latticed Transmission Towers: Current Progress and Future Perspectives
    (Mdpi, 2023) Asyraf, Muhammad Rizal Muhammad; Rafidah, Mazlan; Madenci, Emrah; Ozkilic, Yasin Onuralp; Aksoylu, Ceyhun; Razman, Muhammad Rizal; Ramli, Zuliskandar
    Fibre-reinforced polymer (FRP) composites have been selected as an alternative to conventional wooden timber cross arms. The advantages of FRP composites include a high strength-to-weight ratio, lightweight, ease of production, as well as optimal mechanical performance. Since a non-conductive cross arm structure is exposed to constant loading for a very long time, creep is one of the main factors that cause structural failure. In this state, the structure experiences creep deformation, which can result in serviceability problems, stress redistribution, pre-stress loss, and the failure of structural elements. These issues can be resolved by assessing the creep trends and properties of the structure, which can forecast its serviceability and long-term mechanical performance. Hence, the principles, approaches, and characteristics of creep are used to comprehend and analyse the behaviour of wood and composite cantilever structures under long-term loads. The development of appropriate creep methods and approaches to non-conductive cross arm construction is given particular attention in this literature review, including suitable mitigation strategies such as sleeve installation, the addition of bracing systems, and the inclusion of cross arm beams in the core structure. Thus, this article delivers a state-of-the-art review of creep properties, as well as an analysis of non-conductive cross arm structures using experimental approaches. Additionally, this review highlights future developments and progress in cross arm studies.
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    Damages on prefabricated concrete dapped-end purlins due to snow loads and a novel reinforcement detail
    (Elsevier Sci Ltd, 2020) Aksoylu, Ceyhun; Ozkilic, Yasin Onuralp; Arslan, Musa Hakan
    In prefabricated industrial buildings, damages and collapses may occur under snow loads. If the necessary precautions are not taken, the damage can spread to the whole structure which leads to total collapse. Therefore, it is very crucial for manufacturers to comprehend the nature of the damage and to take necessary precautions to prevent this damage. In this present study, the damages occurred at dapped-end region of prefabricated purlins due to snow load accumulated at the roof and the reasons for these damages were investigated in detail. Pursuant to this goal, comprehensive experimental and numerical studies have been undertaken. 10 specimens with 5 different configurations were tested under four point loading. A novel reinforcement detail and the usage of practical methods used by the manufacturers are selected as main parameters. In all purlins, damages occurred at the dapped-end in shear formation. The experimentally obtained results were compared with field tests and TS9967 design code. It was observed that the specimen with Z type of the proposed novel reinforcement exhibited approximately 30% higher load capacity than that of other specimens. Moreover, the numerical analyses were performed in order to determine optimum Z type reinforcement for dapped-end purlin beams using finite element methods.
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    Effect of the GFRP wrapping on the shear and bending Behavior of RC beams with GFRP encasement
    (Techno-Press, 2022) Ozkilic, Yasin Onuralp; Gemi, Lokman; Madenci, Emrah; Aksoylu, Ceyhun; Kalkan, Ilker
    The need for establishing the contribution of pultruded FRP encasements and additional FRP wraps around these encasements to the shear strength and load-deflection behavior of reinforced concrete beams is the main motivation of the present study. This paper primarily focuses on the effect of additional wrapping around the composite beam on the flexural and shear behavior of the pultruded GFRP (Glass Fiber Reinforced Polymer) beams infilled with reinforced concrete, taking into account different types of failure according to av/H ratio (arch action, shear-tension, shear-compression and pure bending). For this purpose, nine hybrid beams with variable shear span-to-depth ratio (av/H) were tested. Hybrid beams with 500 mm, 1000 mm, and 1500 mm lengths and cross-sections of 150x100 mm and 100x100 mm were tested under three-point and four-point loading. Based on the testing load-displacement relationship, ductility ratio, energy dissipation capacity of the beams were evaluated with comprehensive macro damage analysis on pultruded GFRP profile and GFRP wrapping. The GFRP wraps were established to have a major contribution to the composite beam ductility (90-125%) and strength (40-75%) in all ranges of beam behavior (shear-dominated or dominated by the coupling of shear and flexure). The composite beams with wraps were showns to reach ductilities and strength values of their counterparts with much greater beam depth.
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    Effect of the GFRP wrapping on the shear and bending Behavior of RC beams with GFRP encasement
    (Techno-Press, 2022) Ozkilic, Yasin Onuralp; Gemi, Lokman; Madenci, Emrah; Aksoylu, Ceyhun; Kalkan, Ilker
    The need for establishing the contribution of pultruded FRP encasements and additional FRP wraps around these encasements to the shear strength and load-deflection behavior of reinforced concrete beams is the main motivation of the present study. This paper primarily focuses on the effect of additional wrapping around the composite beam on the flexural and shear behavior of the pultruded GFRP (Glass Fiber Reinforced Polymer) beams infilled with reinforced concrete, taking into account different types of failure according to av/H ratio (arch action, shear-tension, shear-compression and pure bending). For this purpose, nine hybrid beams with variable shear span-to-depth ratio (av/H) were tested. Hybrid beams with 500 mm, 1000 mm, and 1500 mm lengths and cross-sections of 150x100 mm and 100x100 mm were tested under three-point and four-point loading. Based on the testing load-displacement relationship, ductility ratio, energy dissipation capacity of the beams were evaluated with comprehensive macro damage analysis on pultruded GFRP profile and GFRP wrapping. The GFRP wraps were established to have a major contribution to the composite beam ductility (90-125%) and strength (40-75%) in all ranges of beam behavior (shear-dominated or dominated by the coupling of shear and flexure). The composite beams with wraps were showns to reach ductilities and strength values of their counterparts with much greater beam depth.
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    The Effects of Eccentric Web Openings on the Compressive Performance of Pultruded GFRP Boxes Wrapped with GFRP and CFRP Sheets
    (Mdpi, 2022) Madenci, Emrah; Ozkilic, Yasin Onuralp; Aksoylu, Ceyhun; Safonov, Alexander
    Pultruded fiber-reinforced polymer (PFRP) profiles have started to find widespread use in the structure industry. The position of the web openings on these elements, which are especially exposed to axial pressure force, causes a change in the behavior. In this study, a total of 21 pultruded box profiles were tested under vertical loads and some of them were strengthened with carbon-FRP (CFRP) and glass-FRP (GFRP). The location, number and reinforcement type of the web openings on the profiles were taken into account as parameters. As a result of the axial test, it was understood that when a hole with a certain diameter is to be drilled on the profile, its position and number are very important. The height-centered openings in the middle of the web had the least effect on the reduction in the load-carrying capacity and the stability of the profile. In addition, it has been determined that the web openings away from the center and especially the eccentric opening significantly reduces the load carrying capacity. Furthermore, when double holes were drilled close to each other, a significant decrease in the capacity was observed and strengthening had the least effect on these specimens. It was also determined that the specimens reinforced with carbon FRP contribute more to the load-carrying capacity than GFRP.
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    Effects of stirrup spacing on shear performance of hybrid composite beams produced by pultruded GFRP profile infilled with reinforced concrete
    (Springernature, 2022) Ozkilic, Yasin Onuralp; Gemi, Lokman; Madenci, Emrah; Aksoylu, Ceyhun
    Pultruded Glass Fiber-Reinforced Polymer (pultruded GFRP) composite produced by the pultrusion method has become popular in civil engineering applications due to its lightness, corrosion resistance and high strength. However, the use of the pultruded profile combining with reinforced concrete is still limited due to a lack of knowledge. Therefore, the behavior of the pultruded GFRP profile infilled with reinforced concrete beams (hybrid beams) is investigated. This study focused on the effects of stirrup spacing for the hybrid beams. Pursuant to this goal, a total of eight different beams were tested under fourpoint loading. One reference beam without the pultruded profile and seven hybrid beams having different stirrup spacings were considered. Moreover, the hybrid beams with and without stirrups were wrapped by unidirectional GFRP composite to investigate the effects of stirrup spacing on shear capacity of the beams strengthened by GFRP composite. The experimental findings revealed that tightening stirrups increased the load and energy dissipation capacities of the hybrid beams; however, it could not prevent brittle failure. On the other hand, wrapping hybrid beams with GFRP composite increased the load and energy dissipation capacities and also prevented brittle failure regardless of the presence of the stirrups. Therefore, it is strongly recommended that the unidirectional pultruded profiles should be strengthened with 90 degrees GFRP wrapping to have ductile behavior.
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    Effects of Waste Powder, Fine and Coarse Marble Aggregates on Concrete Compressive Strength
    (Mdpi, 2022) Basaran, Bogachan; Kalkan, Ilker; Aksoylu, Ceyhun; Ozkilic, Yasin Onuralp; Sabri, Mohanad Muayad Sabri
    The use of marble wastes in concrete mixtures, causing air and water pollution, has been promoted in the academic and practical spheres of the construction industry. Although the effects of various forms (powder, fine, coarse and mixed) of this waste on the concrete compressive strength has been subject to a decent number of studies in the literature, the difficulties in reaching specific conclusions on the effect of each test parameter constitute a major restraint for the proliferation of the use of marble wastes in the concrete industry. Most of these studies are far from underscoring all of the parameters affecting the concrete compressive strength. Due to the urgent need in the literature for comprehensive studies on concrete mixtures with marble wastes, the results of the axial compression tests on a total of 429 concrete mixtures with marble aggregates were compiled by paying special attention to reporting all test variables (form and content of marble wastes, water-cement ratio, cement content, proportion of coarse and fine aggregates in all aggregates) affecting the concrete strength. In this context, multivariate regression analyses were carried out on the existing test results. These regression analyses yielded to relationships between the change in concrete compressive strength and the test parameters for each and every form of marble waste (powder, fine and coarse aggregate). The study indicated that independent from the form of marble wastes (as powder, fine aggregate or coarse aggregate), aggregate replacements of up to 50% can yield to significant changes in the concrete compressive strength. In addition, the analytical estimates from the developed equations exhibited a high correlation (a least r value of 0.91) with the experimental results from the previous studies, yielding to rather low error values (RMSE value is 5.06 MPa at max). For this reason, the developed equations can consistently predict the changes in concrete compressive strength with varying amounts and forms of the marble aggregates as well as the other test variables.
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    Evaluating Bulky PVA-ECC Mortar Developed with River Sand, Silica Fume, and High-Volume Fly Ash: A Focus on Short- and Long-Term Compressive Strength
    (Springer Heidelberg, 2024) Aswin, Muhammad; Ozkilic, Yasin Onuralp; Aksoylu, Ceyhun; Al-Fakih, Amin
    The construction industry has been increasingly concerned with the environment and sustainability, and one solution is engineered cementitious composites (ECC), which have self-healing, ductility, and strength properties. Researchers have been working to make ECC greener by creating synergistic mechanical interactions between fibers, matrices, and fiber-matrix interfaces. This study developed ECC using local river sand, silica fume, moderate to high-volume fly ash (FA), and bulky PVA fibers, evaluating workability and compressive strength at various testing ages (1, 7, 28, 60, and 180 days). According to the test findings, fresh ECC mortar mixtures exhibit an increase in workability with increasing FA content due to the spherical and glossy form of FA particles. All ECC samples have a compressive strength of over 20 MPa after 1 day, making them high-early compressive strength composites. The sample with the highest compressive strength after 28 days was 111.28 MPa. PVA fibers, FA, and SF contribute to increasing strength while using local river sand as an ingredient in composite mixtures is also beneficial. The samples experienced a bulging process during failure due to the use of oiled PVA fibers. The maximum load before the collapse was attained after a longer period of time where smeared cracks were visible on the samples' surface. Based on the analysis of the compressive strength over a period of more than 28 days, it is clear that both ECC mortar and bulky PVA-ECC samples exhibit sufficient strength stability. It is worth mentioning that as the curing age of ECC increases, there is a gradual increase in strength, although the level of increase is relatively slow.
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    Experimental analysis of reinforced concrete shear deficient beams with circular web openings strengthened by CFRP composite
    (Elsevier Sci Ltd, 2020) Aksoylu, Ceyhun; Yazman, Sakir; Ozkilic, Yasin Onuralp; Gemi, Lokman; Arslan, Musa Hakan
    In this study, two methods of CFRP applications were utilized to strengthen the shear deficient beams with cir-cular holes and a comprehensive experimental program consisting of 11 1/2 scaled specimens was undertaken. The beams with hole diameter (D)/beam height ratio (H) of 0.30, 0.44, 0.64 ratios, symmetrically drilled in shear span were tested under vertical loading. D/H ratio of 0.30 did cause not only a decrease in load carrying capacity but also increased the ductility of the beam. However, significant decreases in load carrying capacities were observed as the hole diameters increase. The load carrying capacity and ductility were significantly improved owing to different CFRP configurations. The fact that the hole diameter and CFRP strengthening method are very important parameters for strengthening is observed. No CFRP strengthening alternative was successful in the beams with a D/H ratio of 0.64. A detailed macro and micro damage analyses are presented.
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    Experimental and analytical investigation of chemical anchors's behaviour under axial tensile
    (Elsevier Sci Ltd, 2020) Musevitoglu, Abdullah; Arslan, Musa Hakan; Aksoylu, Ceyhun; Ozkis, Ahmet
    In this study, to observe the behavior of chemical anchors embedded in concrete under the tensile effect, 108 different anchor specimens were prepared with different parameters as concrete compressive strength, reinforcement bar diameters, anchor depths, sizes of drilled holes, cleanliness of the drilled holes. Pull-out tests were conducted and obtained data were examined with the axial-load capacities and the failure situations. Finally, the depth of anchors, compressive strength and reinforcement diameter were observed to increase the axial-load-bearing capacity. The specimens cleaned with water could bear more axial loads than cleaned using air. For the anchors installed without cleaning the holes, a significant decrease was observed in the axial-load carrying capacities compared to the other two conditions. The ANN algorithm exhibited a 78.3% prediction success compared with other algorithms. The empirical relations in the literature were found to have limited level of prediction success rates according to the ANN's results. (C) 2020 Elsevier Ltd. All rights reserved.
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    Experimental and Analytical Investigation of Flexural Behavior of Carbon Nanotube Reinforced Textile Based Composites
    (Mdpi, 2023) Madenci, Emrah; Ozkilic, Yasin Onuralp; Aksoylu, Ceyhun; Asyraf, Muhammad Rizal Muhammad; Syamsir, Agusril; Supian, Abu Bakar Mohd; Elizaveta, Bobrynina
    In this study, the main goal of this study was to understand the effect of carbon nanotube (CNT) additives on the elastic behaviors of textile-based composites. The materials have three phases: carbon fiber fabric, epoxy matrix, and carbon nanotubes. Different weight fractions of CNTs were used (0% as a reference, 0.3%). Mechanical tests were performed, such as tension and three-point bending beam tests. In addition, the composite material damages were examined in detail. The experimental results show that the samples with CNT carried 9% and 23% more axial tensile force and bending capacity on average than those with NEAT. Besides, it was understood that adding 0.3% by weight of MWCNT increases the tensile modulus by approximately 9%. Finally, the mechanical tensile and bending tests are supported by analytical solutions successfully applied in the literature.
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    Experimental and numerical investigation of bending performance of prestressed purlins having different longitudinal web opening
    (Elsevier Science Inc, 2024) Aksoylu, Ceyhun; Ozkilic, Yasin Onuralp; Celedir, Emrullah; Basaran, Bogachan; Arslan, Musa Hakan
    Variable cross-section pre-stressed precast concrete purlin (PPCP) members are frequently used in industrial buildings. Lightening these elements, which create a significant weight on the roof plane, is extremely important to reduce both concrete consumption and the weight that will affect the earthquake force. The voids left in the purlin bodies can make them even more economical. A series of experimental and numeric studies were carried out to find an answer to this research question. In the study, 8 PPCP beams with different 1/1 geometric scale web opening ratios (ranging between 7.5%similar to 35% depending on the beam length) were tested. At the end of the experimental study, the openings created in the beams did not significantly reduce the load carrying capacity. In addition, bearing capacity of the reference beam was obtained approximately 17% greater than the calculated analytical value. The results of the tests were validated utilizing ABAQUS FEM. Then, a parametric study was performed on 48 models according to three different pre-stressing levels (0.3 P, 0.6 P and 0.9 P) and three different concrete strengths (30 MPa, 40 MPa and 50 MPa). According to results, especially in PPCP with web opening ratios of 27.5% and 32.5%, both initial stiffness and ductility values increased compared to the reference beam. From the numerical models, it was revelead that the decrease in concrete strength caused a capacity loss of up to 17%, especially in beams with the highest opening ratio. It was discovered that the increase in the pre-stress level increased the stiffness and capacity, but the least increase was in the beam with the highest opening ratio.
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    Experimental and numerical investigation of shear strength at dapped end beams having different shear span and recess corner length
    (Elsevier Science Inc, 2023) Aksoylu, Ceyhun; Ozknlnc, Yasin Onuralp; Arslan, Musa Hakan
    The geometric properties of the support region of dapped end beams (DEBs) cause a significant change in the ratio of the distance between the support and suspension reinforcement (a) to the effective depth (d). This ratio is effective in the shear capacity of DEB. In addition, in the ratio of the distance of the load on the beam from the support (av) to the depth of the beam (deff) is also effective on the behavior of the beam under vertical loads. For the first time in the literature, the combined effects of these two ratios on the shear capacity of DEBs was investigated by experimental and numerical methods in this study. Firstly, an experimental study was carried out having 1/1 cross-sectional scale six different DEBs. In the experimental study, while the a/d ratio was kept constant as 1.8, the av/deff ratio was varied between 0.75 and 3. The experiments results indicate that towards increasing the av/deff ratio, the DEBs failed by flexure. The strength of DEBs decreases with an increase in the av/ deff ratio. With smaller av/deff, the DEBs show greater stiffness and ultimate load. Numeric finite element models by using ABAQUS were verified by the load-displacement relationships and damage modes obtained from these experiments. After that, at the parametric stage of the study numeric models were also constructed in order to further investigate the effect of different a/d ratios and av/deff on the strength of DEBs. According to all test and numeric results, it is recommended that DEBs should be placed on the supporting member by considering the minimum a/d ratio. Otherwise, the capacity of the DEBs will be significantly reduced since the damage in the thinned zone will occur at lower load levels. At the end of study, considering the combined effects of a/d and av/ deff, a shear capacity reduction coefficient based on these parameters has been proposed. The shear capacity, which is reduced using the proposed coefficient, approaches the numerical results, which converge to a great extent with the experimental data by 92.46%.
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    Experimental and numerical investigations of steel fiber reinforced concrete dapped-end purlins
    (Elsevier, 2021) Ozkilic, Yasin Onuralp; Aksoylu, Ceyhun; Arslan, Musa Hakan
    Dapped-end beams (DEBs), also known as thinned end beams, are often experienced in shear damages under the effect of vertical loads. Especially if the necessary precautions for thinned ends of reinforced concrete prefabricated purlins on the roofs having standard cross sections are not considered during the design, these purlins can be failed suddenly under the accumulated snow loads. This situation causes the roof to collapse completely. In order to mitigate this drawback, it is aimed to improve shear capacity of the purlins by using steel fiber reinforced concrete (SFRC) without changing the cross section geometry and reinforcement. Pursuant to this goal, experimental and numerical studies have been undertaken. The presence of steel fiber and the aspect ratio are selected as main parameters. The use of SFRC increased energy dissipation and shear capacities approximately 2.58 and 1.53 times, respectively. Moreover, the numerical analyses were performed in order to determine the optimum length of SFRC used in concrete from beam ends and fiber volume ratio to be used, and to investigate the effects of shear span to depth ratio (a/d). The results revealed that fiber volume ratio of 2% and the length of SFRC used up to the point where dapped-end region ends are recommended. Moreover, increasing the ratio of a/d results in a decrease in load carrying capacity.