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    Buckling performance of pultruded glass fiber reinforced polymer profiles infilled with waste steel fiber reinforced concrete under axial compression
    (Techno-Press, 2022) Madenci, Emrah; Fayed, Sabry; Mansour, Walid; Ozkilic, Yasin Onuralp
    This study reports the results of a series of tests of pultruded glass fiber reinforced polymer (P--GFRP) box section composite profile columns, geometrically similar with/without concrete core, containing 0-1-2-3% steel fiber, with different lengths. The recycled steel wires were obtained from waste tyres. The effects of steel fiber ratio on the collapse and size effect of concrete filled P-GFRP columns under axial pressure were investigated experimentally and analytically. A total of 36 columns were tested under compression. The presence of pultruded profile and steel wire ratio were selected as the primary variable. The capacity of pultruded profiles with infilled concrete are averagely 9.3 times higher than the capacity of concrete without pultruded profile. The capacity of pultruded profiles with infilled concrete are averagely 34% higher than that of the pultruded profiles without infilled concrete. The effects of steel wire ratio are more pronounced in slender columns which exhibit buckling behavior. Moreover, the proposed analytical approach to calculate the capacity of P-GFRP columns successfully predicted the experimental findings in terms of both pure axial and buckling capacity.
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    Buckling performance of pultruded glass fiber reinforced polymer profiles infilled with waste steel fiber reinforced concrete under axial compression
    (Techno-Press, 2022) Madenci, Emrah; Fayed, Sabry; Mansour, Walid; Ozkilic, Yasin Onuralp
    This study reports the results of a series of tests of pultruded glass fiber reinforced polymer (P--GFRP) box section composite profile columns, geometrically similar with/without concrete core, containing 0-1-2-3% steel fiber, with different lengths. The recycled steel wires were obtained from waste tyres. The effects of steel fiber ratio on the collapse and size effect of concrete filled P-GFRP columns under axial pressure were investigated experimentally and analytically. A total of 36 columns were tested under compression. The presence of pultruded profile and steel wire ratio were selected as the primary variable. The capacity of pultruded profiles with infilled concrete are averagely 9.3 times higher than the capacity of concrete without pultruded profile. The capacity of pultruded profiles with infilled concrete are averagely 34% higher than that of the pultruded profiles without infilled concrete. The effects of steel wire ratio are more pronounced in slender columns which exhibit buckling behavior. Moreover, the proposed analytical approach to calculate the capacity of P-GFRP columns successfully predicted the experimental findings in terms of both pure axial and buckling capacity.
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    Effect of Block Size on Bearing Strength of Steel Fiber-Reinforced Recycled Aggregate Concrete
    (Springer Heidelberg, 2023) Fayed, Sabry; Madenci, Emrah; Ozkilic, Yasin Onuralp; Tawfik, Taher A.
    For the safe transmission of loads to concrete supports, such as column-foundations, corbels, bridge pedestals, post-tension members, support anchorages, and other forms of superstructure supports, the concrete bearing strength is considered an essential design parameter. The usage of recycled aggregate within concrete is considered environmentally friendly since it diverts rubbish from bulldozing and preserves natural resources. End-hooked steel fibre is an almost substantial enhancer for recycled aggregate concrete characteristics. Never before has the bearing behavior of recycled aggregate concrete been evaluated. Thus, this study provides an experimental evaluation of the bearing strength of steel fiber-reinforced recycled aggregate concrete at different replacement levels (0, 10, 20, 30, 50, and 100%) of recycled concrete aggregate (RCA). The used fraction quantities of steel fiber were 0.5%, 1.5%, and 2%. Three sizes of blocks were manufactured (100 x 100 x 100 mm, 150 x 150 x 150 mm, and 250 x 250 x 250 mm). The ratio of concrete block area to bearing area (A2/A1) was kept constant at 2.5 for all three block sizes. The primary purpose of this research was to examine the impact of block size on bearing stiffness, ultimate slip, and ultimate bearing strength. The findings demonstrated that the bearing stiffness and bearing strength reduced as the block size increased. To assess the ultimate bearing stiffness/strength and normalised ultimate bearing slip, analytical models were employed to develop new proposed equations that unaccounted for the impact of compressive strength, RCA, reinforcing index of steel fibre, and block size. In addition, this research led to the creation of a modified ACI 318 formula that accurately forecasts the bearing strength of concrete depending on block size.
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    Experimental study on using recycled polyethylene terephthalate and steel fibers for improving behavior of RC columns
    (Elsevier, 2023) Fayed, Sabry; Madenci, Emrah; Bahrami, Alireza; Ozkilic, Yasin Onuralp; Mansour, Walid
    In this research, the behavior of RC columns reinforced with recycled polyethylene terephthalate (PET) fibers and steel fibers (SFs) was experimentally investigated. The experimental work included testing of 8 columns with the dimensions of 150 x 150 x 1000 mm subjected to the axial loading up to failure. Three volume fractions (1%, 2%, and 3%) were considered for both PET fibers and SFs. The axial/lateral displacements of the columns and the transverse/vertical strains versus the loads of the bars were recorded. The peak load, yield load, failure mode, ductility, and stiffness of the columns were studied in detail. The effects of plastic fibers (PFs) and SFs on the concrete characteristics were experimentally examined. Using 2% SFs in the mix increased the compressive strength, tensile strength, and toughness of concrete by 12.7%, 87.6%, and 304.8%, respectively. Furthermore, enhancement rates of the ultimate load capacity, stiffness, and ductility of the columns with 2% SFs were 15.6%, 72.6%, and 34.29%, respectively. The ultimate load capacity, initial stiffness, and ductility of the columns reinforced with 1% PF fiber were 9.43%, 62.6%, and 19.4%, respectively, greater than those of the columns without fibers. The columns' capacity was decreased with increasing SFs and PFs over 2%. An equation from ACI was used to predict the columns' capacity and the results agreed well with the experimental results.
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    Flexural Behavior of RC Beams with an Abrupt Change in Depth: Experimental Work
    (Mdpi, 2022) Fayed, Sabry; Madenci, Emrah; Ozkilic, Yasin Onuralp
    The most crucial components in the case of roofs with two levels or a variable floor height are variable depth beams. In order to investigate the flexural behavior of reinforced concrete (RC) beams with varying depths under static loads, experimental research was conducted. Under the four-point bending flexural test, two reference beams with constant depth, six dapped beams at the soffit, and four dapped beams at the top were tested. For all beams with a 150 mm depth, a 100 mm increase in depth occurred at the middle span of the beams. The primary characteristics included the impact of increasing depth, the impact of stirrups' absence and their various ratios, and the characteristics of the longitudinal bars at the locations of sudden depth changes in either the top or bottom bars. Both the cracks' progression and the load-deflection relationship along the beam's length were observed. The ultimate carrying load (Pu) was reduced by 23.56% and 27.35% as a result of the 100 mm increase in the half-span of the beam over the constant depth in case of changes at the top and soffit, respectively. The Pu was increased by a ratio ranging from 20.9% to 31.35% for the bottom dapped beams and by a ratio of 29.79% for the top dapped beams due to the various stirrup ratios in the dapped area. The ductility was significantly impacted by the elevated stirrup ratios in the dapped area. The predicted results and the experimental results matched when the Pu of the tested beams was evaluated using the strut and tie model.
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    Improving Bond Performance of Near-Surface Mounted Steel Ribbed and Threated Rods in the Concrete
    (Springer, 2024) Fayed, Sabry; Madenci, Emrah; Ozkilic, Yasin Onuralp; Zakaria, Mohamed H.
    In this study, the experimental findings of twenty pull-out tests on the bond efficiency of threaded/ribbed steel rods used in near-surface mounting (NSM) are presented. On a groove (20 x 20 mm) that was slotted in one of the sides of a concrete block measuring 250 x 250 x 200 mm, a pull-out experiment was performed. The primary factors are the slot-filling materials (substrate concrete and epoxy paste), bonded length (equal to 5, 7, 10, and 15 times the rod diameter), surface pattern conditions (conventional ribbed reinforcing rebar and threaded bolt), use of nuts or rings welded at the free end of the bonded length, and use of straight or spiral wire welded along the length of the bonded length. The tested specimens' ultimate bond strength, slip, bond stress-slip response, failure patterns, stiffness, and ductility are recorded and assessed. The results showed that the ultimate bond strength and corresponding slip of ribbed rods cemented with epoxy were higher by 11.11% and 199%, respectively, than those of ribbed rods submerged in the substrate. Over the controls, all NSM epoxy-rods exhibited a greater ductility. As the bonded length increased, the ultimate bond strength of NSM rods fell by 12-32%. As the bonded length increased, the stiffness decreased. On the other hand, the ductility of NSM epoxy-rods increased as the bonded length increased. All applied schemes such as nuts, rings, longitudinal bars, and spiral bars significantly improved the ultimate bond strength (maximum = 25.93%) and corresponding slip (maximum = 166.67%) of NSM threaded rods as compared to the control ones.
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    Improving Bond Performance of Near-Surface Mounted Steel Ribbed and Threated Rods in the Concrete
    (Springer, 2024) Fayed, Sabry; Madenci, Emrah; Ozkilic, Yasin Onuralp; Zakaria, Mohamed H.
    In this study, the experimental findings of twenty pull-out tests on the bond efficiency of threaded/ribbed steel rods used in near-surface mounting (NSM) are presented. On a groove (20 x 20 mm) that was slotted in one of the sides of a concrete block measuring 250 x 250 x 200 mm, a pull-out experiment was performed. The primary factors are the slot-filling materials (substrate concrete and epoxy paste), bonded length (equal to 5, 7, 10, and 15 times the rod diameter), surface pattern conditions (conventional ribbed reinforcing rebar and threaded bolt), use of nuts or rings welded at the free end of the bonded length, and use of straight or spiral wire welded along the length of the bonded length. The tested specimens' ultimate bond strength, slip, bond stress-slip response, failure patterns, stiffness, and ductility are recorded and assessed. The results showed that the ultimate bond strength and corresponding slip of ribbed rods cemented with epoxy were higher by 11.11% and 199%, respectively, than those of ribbed rods submerged in the substrate. Over the controls, all NSM epoxy-rods exhibited a greater ductility. As the bonded length increased, the ultimate bond strength of NSM rods fell by 12-32%. As the bonded length increased, the stiffness decreased. On the other hand, the ductility of NSM epoxy-rods increased as the bonded length increased. All applied schemes such as nuts, rings, longitudinal bars, and spiral bars significantly improved the ultimate bond strength (maximum = 25.93%) and corresponding slip (maximum = 166.67%) of NSM threaded rods as compared to the control ones.
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    Improving bond performance of ribbed steel bars embedded in recycled aggregate concrete using steel mesh fabric confinement
    (Elsevier Sci Ltd, 2023) Fayed, Sabry; Madenci, Emrah; Ozkilic, Yasin Onuralp; Mansour, Walid
    To investigate the bond behaviour of passively confined-recycled aggregate concrete (RAC), centre pull out tests were carried out on deformed steel bar with a diameter (O) of 12 mm. The recycled concrete aggregate (RCA) replacement ratios are 0, 30, 50, and 100 %. To investigate local bond strength, a short anchorage bonded length (La) of 10 was chosen. Steel mesh fabric (SMF) cylinders were used to confine the RAC around the bonded length of the bar. SMFs have diameters of 4O and 6O. SMF cylinder reinforcement ratios were estimated to be 0, 2.33, 3.04, 3.5, and 4.56 %. To accurately estimate maximal rising ratios in bond strength response owing to RAC confinement using SMFs, all specimens are intended to fail in the pull out mode (rather than the splitting mode). Unconfined and confined pull out specimens were tested for failure mechanism, ultimate local bond strength, bond stress-slip response, and ductility. When compared to similar unconfined specimens, confinement utilising SMFs dramatically improved bond stress-slip behaviour for all specimens including RCA. Ultimate bond strengths of RAC-unconfined specimens were 3.7-24.5 % lower than those of NAC-unconfined specimens, whereas ulti-mate slips of RAC-unconfined specimens were 25-140 % higher than those of NAC-unconfined specimens. Due to the usage of SMF cylinders at various levels of RCA, the ultimate bond strength of all confined specimens was dramatically increased when compared to unconfined specimens. When compared to a control unconfined NAC-specimen, the ductility of unconfined specimens containing 30 %, 50 %, and 100 % RCA decreased by 5.7, 18.6, and 39.6 %, respectively. In comparison, when compared to similar unconfined specimens, the maximum rising ratios in the ductility of confined specimens containing 0 % RCA, 30 % RCA, 50 % RCA, and 100 % RCA are 44.2 %, 77.9 %, 52.4, and 117.7 %, respectively. A novel proposed formula is developed to compute the ultimate bond strength of RAC while taking into account the influence of concrete grade, RCA content, concrete confinement via SMF, and transverse ties, and its results agree with the experimental results.