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RISS 인기검색어
- 검색키워드
- 저자 : Hashem Jahangir (검색결과 3 건)
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Numerical Study of Bond – Slip Mechanism in Advanced Externally Bonded Strengthening Composites
Hashem Jahangir,Mohammad Reza Esfahani 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.11
Detrimental effects of various environmental phenomena such as earthquakes on Reinforced Concrete (RC) structures make repairing, strengthening and rehabilitation necessary to satisfy current code requirements. For achieving compliance and safer structures, many efforts involve attaching composites to damaged or identified damage-prone zones of RC members. In recent years, a type of novel composites, named Fiber Reinforced Cementitious Matrix (FRCM) has been developed which comprises of two internal and external layers of mineral cement based matrix cover, reinforced with one or more layers of fiber. In any newly developed composite, among the first steps for performance evaluation is the investigation into bond characteristics of the various structural elements. In this respect, direct shear tests, owing to their straightforward outputs, are the most aptly utilized kind of tests in order to study behavior of composite bonds. This paper investigates various aspects of FRCM bond performance on concrete blocks in shear tests. A numerical bond - slip relation was developed based on experimental data on FRCM strengthened concrete blocks. The results obtained from the numerical model show good agreement with the experimental results and provide in depth information about stress - slip relation, load responses, width effect as well as slip and strain profiles in FRCM composites.
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Investigating loading rate and fibre densities influence on SRG - concrete bond behaviour
Hashem Jahangir,Mohammad Reza Esfahani 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.6
This work features the outcomes of an empirical investigation into the characteristics of steel reinforced grout (SRG) composite - concrete interfaces. The parameters varied were loading rate, densities of steel fibres and types of load displacement responses or measurements (slip and machine grips). The following observations and results were derived from standard single-lap shear tests. Interfacial debonding of SRG - concrete joints is a function of both fracture of matrix along the bond interface and slippage of fibre. A change in the loading rate results in a variation in peak load (Pmax) and the correlative stress (σmax), slip and machine grips readings at measured peak load. Further analysis of load responses revealed that the behaviour of load responses is shaped by loading rate, fibre density as well as load response measurement variable. Notably, the out-of-plane displacement at peak load increased with increments in load rates and were independent of specimen fibre densities.
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Hashem Jahangir,Danial Rezazadeh Eidgahee,Mohammad Reza Esfahani 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.6
Composite materials are effective in forming externally bonded reinforcements which find applications related to existing structures repair, attributed to their high strength-to-weight ratio and ease of installation. Among various composites, fibre reinforced polymers (FRP) have somewhat been largely accepted as a commonly utilized composite for such purposes. It is only recently that steel fibres have been considered as additional members of the FRP fibre family, intuitively termed as steel reinforced polymer (SRP). Owing to its low cost and permissibility of fibre bending at sharp corners, SRP is rapidly becoming a viable contender to other FRP systems. This paper investigates the bond behaviour of SRP-concrete joints with different bonded lengths (50, 75, 100, 150 and 300 mm) and widths (15, 30, 40, 50, and 75 mm) using single-lap shear tests. The experimental specimens contain SRP strips with a fixed density of steel fibres (0.472 cords/mm) bonded to the face of concrete prisms. The load responses were obtained and compared in terms of corresponding load and slip boundaries of the constant region and the peak loads. The failure modes of SRP composites are discussed, and the range of effective bonded length is evaluated herein. In the end, a new analytical model was proposed to estimate the SRP-concrete bond strength using a genetic algorithm, which outperforms 22 existing FRP-concrete bond strength models.
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