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RISS 인기검색어
- 검색키워드
- 저자 : Kiachehr Behfarnia (검색결과 4 건)
- 무료
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A numerical study on behavior of CFRP strengthened shear wall with opening
Kiachehr Behfarnia,Ahmadreza Shirneshan 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.2
Concrete shear walls are one of the major structural lateral resisting systems in buildings. In some cases, due to the change in the occupancy of the structure or functional requirements like architectural and even mechanical ones, openings need to be provided and installed in structural walls after their construction. Providing these openings may significantly influence the structural behavior of the constructed wall. This paper considers the results of a nonlinear finite element analysis of shear walls with opening strengthened by carbon fiber reinforced polymer (CFRP) strips with different configurations. Details of bond-slip constitutive model of link elements to simulate the connections of FRP strips to concrete surface is presented. The proposed model in this research has been validated using experimental results available in the literature. The results indicated that the proposed configuration of CFRP strips significantly improved the lateral resistance and deformation capacity of the shear walls with opening.
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Arash Sedaghatdoost,Kiachehr Behfarnia,Hamidreza Moosaei,Mohammad Bayati,Mohammad Sadegh Vaezi 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.1
The properties of mortars containing waste glass powder (WGP) as a cement substitute for sustainable construction at various high temperatures were investigated. For this purpose, specimens from four mixtures with WGP at various percentage levels of 0, 5, 10 and 15% were prepared and exposed to the specified temperatures. After that, the compressive and flexural strength were determined at high temperatures. The mass loss was also measured by weighing the samples before and after exposing to the high temperatures. The microstructure of mortars was analyzed by petrographic examination. Based on the obtained results, incorporation of WGP as partial replacement of cement could improve strength characteristics of the mortars at the elevated temperatures up to 17%. Also, the optimum ratio of cement replacement level was found to be 10%. In addition, the petrographic images of the mortars showed that at the same time with the strength loss of specimens, the red discoloration of WGP occurred that is attributed to the oxidation of iron compounds that starts at temperatures above 200 ℃.
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A numerical study on the seismic behavior of a composite shear wall
Reza Naseri,Kiachehr Behfarnia 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.22 No.3
Shear walls are one of the important structural elements for bearing loads imposed on buildings due to winds and earthquakes. Composite shear walls with high lateral resistance, and high energy dissipation capacity are considered as a lateral load system in such buildings. In this paper, a composite shear wall consisting of steel faceplates, infill concrete and tie bars which tied steel faceplates together, and concrete filled steel tubular (CFST) as boundary columns, was modeled numerically. Test results were compared with the existing experimental results in order to validate the proposed numerical model. Then, the effects of some parameters on the behavior of the composite shear wall were studied; so, the diameter and spacing of tie bars, thickness and compressive strength of infill concrete, thickness of steel faceplates, and the effect of strengthening the bottom region of the wall were considered. The seismic behavior of the modeled composite shear wall was evaluated in terms of stiffness, ductility, lateral strength, and energy dissipation capacity. The results of the study showed that the diameter of tie bars had a trivial effect on the performance of the composite shear wall, but increasing the tie bars spacing decreased ductility. Studying the effect of infill concrete thickness, concrete compressive strength, and thickness of steel faceplates also showed that the main role of infill concrete was to prevent buckling of steel faceplates. Also, by strengthening the bottom region of the wall, as long as the strengthened part did not provide a support performance for the upper part, the behavior of the composite shear wall was improved; otherwise, ductility of the wall could be reduced severely.
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Abdul Hossein Paknejadi,Kiachehr Behfarnia 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.8
Structural engineers have restrictions on the use of headed bars to reduce the congestion of the reinforcement in the joints have limitations. Some of these limitations are related to the type of concrete used and the clear space between the headed bars. In the present research, 6 exterior joint specimens with a scale of 2/3 scale constructed and then placed under cyclic loading. These tests were conducted in order to investigate the seismic criteria of these types of joints in three ways: 1) changing the type of concrete used from the normal one to the self-consolidating one; 2) decreasing the clear spacing existing between the headed bars to 2.06db, and 3) applying two layers of headed bars that have the vertical spacing of up to 2.50db from each other. The obtained results revealed that applying the self-consolidating concrete (SCC) led to the improvement of the joints seismic behavior; also, the joint performance was still acceptable with the reduction of the clear spacing between the bars and the use of two layers of headed bars.
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