Fatigue behavior of RC T-beams strengthened in shear with EB CFRP L-shaped laminates |
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| Affiliation: | 1. Department of Construction Engineering, University of Quebec, École de Technologie Supérieure, Montreal, QC H3C 1K3, Canada;2. Department of Construction Engineering, University of Quebec, École de Technologie Supérieure, 1100 Notre-Dame St. West, Montreal, QC H3C 1K3, Canada;1. Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, Beijing Key Laboratory of Bio-Inspired Energy Materials and Devices, School of Chemistry and Environment, Beijing University of Aeronautics and Astronautics, Beijing 100191, PR China;2. China Academy of Machinery of Science & Technology, Beijing 100044, PR China;3. State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116023, PR China;1. Tomsk Polytechnic University, Savinykh St., 7, 634028, Russia;2. Novouralsk Research & Design Centre, P.O. Box 45, 624130 Novouralsk, Russia;1. ENDIF, Dep. of Eng., University of Ferrara, 44121 Ferrara, Italy;2. ISISE, Dep. of Civil Eng., Univ. of Minho, Azurém, 4810-058 Guimarães, Portugal;1. School of Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom;2. Shire Structures, Bromsgrove B61 0SZ, United Kingdom |
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| Abstract: | The use of externally bonded carbon fiber-reinforced polymer (EB-CFRP) to strengthen deficient reinforced concrete (RC) beams has gained in popularity and has become a viable and cost-effective method. Fatigue behavior of RC beams strengthened with FRP is a complex issue due to the multiple variables that affect it (applied load range, frequency, number of cycles). Very few research studies have been conducted in shear under cyclic loading. The use of prefabricated CFRP L-shaped laminates (plates) for strengthening RC beams under static loading has proven to be technically feasible and very efficient. This study aimed to examine the fatigue performance of RC T-beams strengthened in shear for increased service load using prefabricated CFRP L-shaped laminates. The investigation involved six laboratory tests performed on full-size 4520 mm-long T-beams. The specimens were subjected to fatigue loading up to six million load cycles at a rate of 3 Hz. Two categories of specimens (unstrengthened and strengthened) and three different transverse-steel reinforcement ratios (Series S0, S1, and S3) were considered. Test results were compared with the upper fatigue limits specified by codes and standards. The specimens that did not fail in fatigue were then subjected to static loading up to failure. The test results confirmed the feasibility of using CFRP L-shaped laminates to extend the service life of RC T-beams subjected to fatigue loading. The overall response was characterized by an accelerated rate of damage accumulation during the early cycles, followed by a stable phase in which the rate slowed significantly. In addition, the strains in the stirrups decreased after the specimens were strengthened with CFRP, despite the higher applied fatigue loading. Moreover, the addition of L-shaped laminates enhanced the shear capacity of the specimens and changed the failure mode from brittle to ductile under static loading. Finally, the presence of transverse steel in strengthened beams resulted in a substantially reduced gain in shear resistance due to CFRP, confirming the existence of an interaction between the transverse steel and the CFRP. |
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| Keywords: | Reinforced concrete B Fatigue B Strength A Laminates |
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