Browsing by Author "Uysal, Y."

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Shear Behavior of Reinforced Concrete Beams Strengthened With a 45° Inclined MSS Technique: Parametric Study of Shear Span-To Ratio and Beam Height
(Taylor and Francis Ltd., 2025) Aksoylu, C.; Fadimana, Bas; Uysal, Y.; Basaran, B.; Arslan, M.H.; Özkılıç, Y.O.
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.
Shear Strengthening of Sub-Standard Reinforced Concrete Beams with CFRP: Influence of Fiber Areal Weight, Wrap Scheme and Concrete Strength
(Elsevier Ltd, 2025) Sarı Alav, Deniz; Uysal, Y.; Aksoylu, C.; Arslan, M.H.
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 high-strength 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. © 2025 Institution of Structural Engineers. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Citation - WoS: 4
Citation - Scopus: 4
Strengthening Shear Deficiency in Undamaged Reinforced Concrete Beams Using Innovative 45° Mechanical Steel Stitches
(Elsevier Ltd, 2023) Aksoylu, C.; Uysal, Y.; Özkılıç, Y.O.; Başaran, B.; Arslan, M.H.
In this study, beams with insufficient shear capacity were reinforced with U-shaped Mechanical Steel Stitches (MSS), which is an innovative approach. MSSs were applied at an angle of 45 degrees along the shear span on both faces of the beam body. A total of eight shear beam specimens, one of which is a reference and the other seven with different MSS spacing, were examined under vertical loads. The diameter, anchorage depth and mechanical properties of the MSSs and the geometry, longitudinal and transverse reinforcements of the reinforced concrete beam were kept constant. By changing the MSS intervals (from d/5 to d), the change was investigated in terms of strength, ductility, stiffness and energy consumption capacities. As a result of the study, 54% increase in shear capacity was observed in the beam with the most tightened MSS spacing (d/5). However, the nominal yield and total energy consumption capacity increased by 144% and 366%, respectively, compared to the reference beam. While splitting damage was most frequently observed in the MSS application with d/5, the damage turned into diagonal tension collapse, which is more abrupt and brittle as the spacing increases to d/2 range. As the MSS interval in beams increased from d/5 to d/2, the nominal yield stiffness of the beams showed a decreasing trend between 2.1% and 21.2% compared to the reference beam. Based on the experimental results, the developed novel strengthening methods can applicable to beams if the interval of MSS spacing is tightened enough. © 2023 Institution of Structural Engineers