دانلود رایگان مقاله انگلیسی مطالعات عنصری تحلیلی و محدودی بر رفتار FRP تقویت کننده های پرتوهای RC تحت چرخش به همراه ترجمه فارسی
|عنوان فارسی مقاله:
|مطالعات عنصری تحلیلی و محدودی بر رفتار FRP تقویت کننده های پرتوهای RC تحت چرخش
|عنوان انگلیسی مقاله:
|Analytical and finite element studies on behavior of FRP strengthened RC beams under torsion
|رشته های مرتبط:
|مهندسی عمران، سازه و زلزله
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|الزویر – Elsevier
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۲٫ مروری بر ادبیات
بخشی از مقاله انگلیسی:
Fiber reinforced polymer (FRP) is a widely used strengthening material for reinforced concrete members owing to its various advantages such as light weight, ease of application, high strength and stiffness. Faulty design, unexpected loads, change in usage type, construction errors are few of the reasons which necessitate the strengthening of existing structures. The behavior of FRP strengthened reinforced concrete (RC) members is more complex than the unstrengthened RC members and therefore, a clear understanding of their behavior under different types of loading is important. A plethora of studies has been conducted in the past to understand the behavior of FRP strengthened RC beams under flexure and shear [1–۲]. However, torsional behavior has not been given significant attention despite its frequent occurrence in many important engineering structures. Though torsion is considered as a secondary effect for most general cases, it becomes critical in cases such as connecting beams, outrigger bent, and bridge columns. Therefore, it is important to understand the behavior of RC members under torsional loading in detail. Moreover, the efficiency of FRP strengthening in terms of strength and stiffness improvement under torsional loading is relatively not very well understood. This is due to the complex nature of interaction effects of FRP on the softening and confinement of concrete and increased tension stiffening behavior of concrete. This study tries to fill the knowledge gap existing in this vital area of research by carrying out analytical and FE studies. Behavior of FRP strengthened RC beam can be understood from the assembly of membrane elements with additional equilibrium and compatibility conditions. Fig. 1 describes the shear flow in an FRP strengthened RC beam subjected an external torque ‘T’. Membrane element ‘E’ subjected to shear flow ‘q’ is also shown in Fig. 1.
۲٫ Review of literature
Few researchers in the past have experimentally investigated the behavior of FRP strengthened RC members under torsional loading. Ghobarah  experimentally studied the effect of CFRP (Carbon fiber reinforced polymer) and GFRP (Glass fiber reinforced polymer) strengthening on torsional behavior RC beams. Different wrapping configurations were used in this study and the authors concluded that 45 degree orientation of the fiber is more effective than 0 and 90 degree oriented configurations in increasing the torsional strength. Zhang et al.  investigated the torsional behavior of RC beams using CFRP sheets as external reinforcement. Panchacharam and Belarbi  conducted an experimental study of the torsional behavior of RC beams strengthened with FRP composites. Number of plies, fiber orientation, and number of beam faces strengthened were the study parameters. Authors concluded that strengthening with GFRP sheets significantly increases ultimate strength and corresponding twist. They also noted that fibers oriented at 90 degrees to the beam axis provided the most effective confinement. Ronagh and Dux ; and Hii and Al-Mahiadi  also investigated the effect of FRP on the torsional behavior of RC members. They concluded that externally bonded CFRP increased cracking and ultimate strength by 40% and 78% respectively compared to control specimens. Jing and Grunberg  investigated the behavior of reinforced concrete box beams strengthened with CFRP sheets under combined action of bending, shear and torsion and proposed a mathematical model based on diagonal compression field theory. This model was basically developed for box beams subjected to low bending torque ratios and shear torque ratios. Ameli et al.  studied the effect of CFRP and GFRP on the torsional behavior of RC beams. The authors also performed a numerical study using ANSYS finite element software and concluded that the finite element model was able to capture the ultimate torque and discrepancy from the experimental observations are found to be less than 13% but post crack behavior is less accurately captured. He et al.  studied the effect of CFRP on behavior of damaged RC bridge columns that had fractured longitudinal bars. These columns were externally strengthened in both longitudinal and transverse directions. The authors found that strengthened columns were successful in regaining the strength of columns without fractured bars. He et al.  investigated the torsional behavior of RC damaged column strengthened with CFRP strips in both longitudinal and transverse directions. They found that CFRP strengthening was able to restore the strength and stiffness of damaged columns. Similar research was carried by Yang et al. . The authors experimentally investigated the behavior of FRP strengthened RC bridge columns which had buckled longitudinal bars before strengthening. These strengthened columns were tested under constant axial load and cyclic lateral load that results the combined action of bending, shear, and torsion. The authors concluded that columns recovered their ability to perform against cyclic loading in terms of lateral strength and ductility. Chalioris  proposed an extended analytical model for FRP strengthened RC beams subjected to torsion for which classical softened truss model forms the basis. This model utilizes softened and FRP confined compression curve for concrete. Author concluded that the proposed model is found satisfactory in predicting the post crack stiffness. Moslehy et al.  studied the influence of FRP on the constitutive relationships of reinforced concrete elements. Researchers modified conventional softening coefficient to take the effect of FRP into account. Ganganagoudar et al.  investigated the torsional behavior of circular RC bridge columns under torsional loading. Authors proposed an improved SMMT for circular columns which considering the strain gradient effect and modified tension stiffening relationships. The present study is motivated from improving the existing analytical models by implementing better constitutive relationships of concrete in compression and tension. Experimental data available from the literature is used for comparison to check the validation of the results of proposed analytical and finite element models.