Yazar "Uysal, Yusuf" seçeneğine göre listele

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    Effect of stirrup spacing on strengthening beams with insufficient shear capacity using innovative mechanical steel stitches
    (Ernst & Sohn, 2025) Aksoylu, Ceyhun; Uysal, Yusuf; Basaran, Bogachan; Ozkilic, Yasin Onuralp; Arslan, Musa Hakan
    This study investigates experimentally and analytically the effect of stirrup spacing variation on the behavior of reinforced beams in the 45 degrees-inclined innovative mechanical steel stitches (MSSs) application for the strengthening of reinforced concrete beams with insufficient shear capacity. Within the scope of the experimental study, four-point loading tests were carried out under vertical loads by selecting stirrup spacing (250, 350, and 450 mm) and MSS spacing (d/3, d/2.5, d/2, d/1.7, and d/1.4) as variable parameters (d is effective depth of beam). In this context, a total of 12 beam specimens with dimensions of 125 x 250 x 2500 mm each with 250 and 450 mm stirrup spacing were produced, one reference specimen with each stirrup spacing and specimens reinforced with five different MSS spacings were tested; in addition, the test results of a reference beam with 350 mm stirrup spacing and beams reinforced with six different MSS spacings in the literature were used for comparison. Within the scope of the analytical study, the MSS spacing required for the beams to reach the flexural capacity was investigated by selecting the ratio of tensile reinforcement and the presence/absence of compressive reinforcement as variable parameters. In the study, the changes in failure mode, strength, ductility, stiffness, and energy consumption capacities of beams due to different stirrup and MSS spacings were analyzed. According to the experimental results obtained at the end of the study, it was observed that the reference beam with 250 mm stirrup spacing carried 32% and 35% more load than the reference beams with 350 and 450 mm spacing, respectively. Tightening the MSS up to 75 mm increased the shear capacity of beams with 450, 350, and 250 mm stirrup spacing up to 46.1%, 37.4%, and 23.5%, respectively. As the stirrup spacing of the reinforced beams decreased, the contribution of the MSS application to the shear capacity decreased. In addition, the failure mode of the beams changed from diagonal tension mode to splitting mode by increasing the MSS spacing. According to the analytical results, it was observed that MSS contributed more to the flexural capacity in beams with low longitudinal reinforcement ratio, and the performance of MSS was significantly improved in the absence of compression reinforcement.
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    Effects of shear wall ratio and location on Earthquake performance of reinforced concrete buildings having different ribbed slab configurations
    (Elsevier, 2025) Uysal, Yusuf; Serdar, Ali; Aksoylu, Ceyhun; Arslan, Musa Hakan
    This study investigates the earthquake performance of reinforced concrete buildings designed with ribbed slab system. Analyses were performed on hypothetical models representing residential buildings in Gaziantep/Islahiye region. In this study, a total of 18 shear wall-frame structure models with three different shear wall placements in accordance with TBEC-2018 were analyzed. Wall density index (0.003, 0.005 and 0.008), shear wall locations defined as M1 (vertically placed on the outer axes), M2 (center-mounted), and M3 (parallel to the outer axes), and ribbed slab placements (parallel and staggered) are considered as variable parameters. The seismic performance of the structures was evaluated using linear and nonlinear analyses. Nonlinear static pushover analyses were used to compare capacity curves, overstrength factor, interstory drift ratios, base shear forces, overturning moments, and second-order effects for each model. As the wall density index increased from 0.003 (%25) to 0.008 (%75), the initial stiffness increased by 158 %, but this increase decreased the plastic deformation capacity and modal displacement values. Models M1 and M3 with walls positioned on the outer axes provided 20.53 % more load carrying capacity than Model M2 with the central wall. The uncracked section shell exhibited 19 %-83 % stiffer behavior, while the cracked sections absorbed more energy. No significant effect of the slab rib arrangement (parallel/staggered) on the stiffness and period was observed. As the shear wall ratio increased, the torsional period decreased by up to 55 %, and the highest torsional strength was achieved in Model M3. Low shear wall ratio models exceeded code drift limits and showed increased interstory drift differences. The results showed that shear wall placement and ratios are critical to seismic performance, and that TBEC-2018 effectively enhances safety in ribbed slab systems.
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    Multistage evaluation of strengthening strategies for achieving adequate seismic performance in reinforced concrete school buildings
    (Elsevier Science Inc, 2026) Timurlenk, Piril; Uysal, Yusuf; Arslan, H. Derya; Arslan, M. Hakan
    It is crucial that socially important structures, such as schools, remain operational without sustaining damage after earthquakes. However, some public buildings in Turkey have not received adequate engineering services, making it necessary to evaluate the seismic performance of these structures and apply appropriate strengthening methods when deemed necessary. This study comprehensively examines potential strengthening strategies and their effects on various school buildings in T & uuml;rkiye, a country located in a highly active seismic zone with a vulnerable public building stock. Three commonly used school building types (8, 14, and 22 classrooms) were selected. Parametric studies were conducted on buildings with insufficient seismic performance, evaluating different strengthening scenarios. Input parameters included varying peak ground acceleration (PGA) values reflecting regional seismicity, diverse local soil conditions, and different material strengths. Strengthening strategies such as reinforced concrete jacketing, shear wall addition and FRP wrapping were applied to columns. A total of 432 structural models were analyzed. One or more of these methods were used to achieve the target performance level. Results were interpreted based on structural strength, period, over-strength factor and cost. It was found that the combination of shear wall addition and jacketing had the most significant impact on structural period, leading to notable reductions in spectral displacement demands. However, this combination also resulted in higher over-strength factors and increased strengthening costs compared to other methods. The study concludes that the absence of over-strength targets for retrofitted buildings in seismic codes is a critical gap and should be addressed in future code revisions.
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    Shear behavior of reinforced concrete beams strengthened with a 45° inclined MSS technique: Parametric study of shear Span-to-depth ratio and beam height
    (Taylor and Francis Ltd., 2025) Aksoylu, Ceyhun; Baş, Fadimana; Uysal, Yusuf; Basaran, Bogachan; Arslan, Musa Hakan; Özkılıç, Yasin Onuralp
    Current methods for strengthening reinforced concrete beams with insufficient shear capacity have structural and practical limitations. This study experimentally investigated the performance of a 45° inclined Mechanical Steel Stitches (MSS) technique under four-point loading. 17 beams (3 reference, 14 strengthened) with shear span-to-depth ratios (av/d = 2.5, 3.3, 4.9) and section heights (250, 360 mm) were tested, while a group with av/d = 3.3 and 250 mm height was adopted from the literature for comparison. Beams were evaluated in terms of maximum load, displacement, energy dissipation, stiffness, ductility, and failure modes. Results showed that MSS was highly effective, particularly at low av/d ratios. The maximum capacity increase reached 86.2% for av/d = 2.5, decreasing to 50.6% at av/d = 3.3 and 14.9% at av/d = 4.9, where diagonal cracks intersecting MSS anchor holes limited the contribution. The optimum MSS spacings were determined as d/2.5 for av/d = 2.5 and d/5 for av/d = 3.3 and 4.9. Increasing beam height from 250 to 360 mm reduced MSS effectiveness by 5.4–27.5%. All reference beams failed in brittle diagonal tension, while strengthened beams exhibited splitting (43%) or combined diagonal tension–splitting (29%). Decreasing MSS spacing shifted failure from diagonal tension to splitting. Overall, the inclined MSS technique proved effective and practical for strengthening shear-deficient beams, offering guidance for design and application. © 2025 Taylor & Francis Group, LLC.
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    Shear strengthening of sub-standard reinforced concrete beams with CFRP: Influence of fiber areal weight, wrap scheme and concrete strength
    (Elsevier Science Inc, 2025) Alav, Deniz Sari; Uysal, Yusuf; Aksoylu, Ceyhun; Arslan, Musa Hakan
    This study investigates the effectiveness of carbon fiber-reinforced polymer (CFRP) in enhancing the performance of reinforced concrete beams with insufficient shear reinforcement-a common issue in existing low- and highstrength reinforced concrete buildings. A total of 35 one-third scale beams were tested under four-point bending, considering varying concrete strengths (5-70 MPa), CFRP areal weights (300 and 900 g/m2), and wrapping configurations (full (F), U-shaped (U), and side (S)). Key parameters such as load-displacement behavior, energy dissipation, ductility, and stiffness were analyzed in detail. The results demonstrated that CFRP strengthening increased shear capacity by up to 154 % in low-strength concrete (5-20 MPa), while the improvement was limited to 47.2 % in high-strength concrete. Failure modes were significantly influenced by wrapping type: full wrapping led to a 90 % shift from shear to flexural failure, whereas U-shaped and side wrapping achieved only 40 % and 10 % conversion, respectively. Full wrapping also yielded the highest gains in energy dissipation and ductility, while side wrapping alone was largely ineffective. Interestingly, increasing CFRP areal weight did not result in proportional performance gains; in many cases, the 300 g/m2 application outperformed the 900 g/m2 variant. This suggests that poor interfacial bonding and inadequate epoxy impregnation may hinder the effectiveness of higher areal weight configurations. In conclusion, concrete strength, wrapping type, and CFRP areal weight must be considered collectively in shear strengthening strategies. Among these, full wrapping offers the most consistent and reliable improvements in shear capacity, ductility. and energy dissipation.