جستجوی مقالات مرتبط با کلیدواژه "برش" در نشریات گروه "عمران"

Due to their lightweight, high tensile strength, and ease to install on irregular surfaces, the use of FRP systems for the repair and strengthening of reinforced concrete structures has become an accepted practice within civil engineering community and codes. Extensive research has been conducted on structural members to identify the improvement in their flexural and axial capacity due to FRP strengthening. However, the analytical and experimental studies on shear strengthening with FRP systems, especially exact determining FRP contribution, are limited. This study provides a multi-layer artificial neural network and group method of data handling approach for predicting the shear contribution of FRP in RC beams strengthened by externally bonded FRP sheets. To achieve the main purpose; ultimate strain of FRP, thickness of FRP, elastic modulus of FRP, width, spacing and angle of FRP sheet, effective depth of FRP, width and of effective depth of beam, compressive strength of concrete, and shear span to depth ratio were considered as input parameters while the shear contribution of the FRP is calculated as the target one. In order to verify the validity of the proposed models, a comparative assessment was conducted between experimental results and predicted values obtained directly from the models and existing guideline equations such as ACI 440, fib-TG9.3, and JSCE. The results indicate that the proposed models could predict the shear contribution of FRP in RC beams strengthened by FRP sheets with a good degree of precision and can be used as a confident approach for pre-design concrete beams strengthened with externally bonded U-shape FRP plates.

The use of fiber reinforced polymers, FRP, is one of the methods for strengthening and retrofitting concrete structures. In this research, the strengthening of reinforced self-compacting concrete beams against shear, torsion and bending has been investigated using GFRP. For reinforcing the beams against shear, bending and torsion, the strips of GFRP were used in the forms of U-shape, straight on the bottom surface and screwed around the beams respectively. In this study, the experimental results were compared with the results of the numerical models and their accuracies were confirmed. Then reinforcement sheets were applied in one and two layers on concrete beam models. By studying the numerical results obtained from Abaqus software, it was observed that with the increase of cracks in the concrete beams, their stiffness decreased and then the stresses were tolerated by the adhesive layers and the GFRP sheets, which has led to an increase in the bearing capacity of the beams. The results of numerical finite elements modeling show that by reinforcing the concrete beams with one layer of GFRP, the load bearing capacities of the beams improved in shear and torsion about 32% and 47% respectively. Moreover, if two layers of reinforcement sheets were used, the shear and torsion capacities of the beams increased about 45% and 61% respectively. The bending capacities of the concrete beams strengthened with one and two layers of GFRP increased up to 32% and 48% respectively.

Dowel action and aggregate interlocking are the main mechanisms for shear transfer at RC joints and cracks. Dowel action is the only transfer agent across precast joints like those in some kinds of RC pavements. Behavior of RC pavement is affected by the load transfer capability at the joint. Efficiency of such a structure is directly related to the transferred loads. Therefore, analyzing joint and crack performance in pavements has an important role and also depends on using proper behavioral models to simulate load transfer mechanism. In this paper, shear transfer mechanism through dowel bars in RC pavements has been investigated based on the beam on elastic foundation theory (BEF) and has been extended to beam on inelastic foundation (BIF) to take account of the nonlinear interaction between concrete and reinforcement bars. In fact, the main objective is to provide a method which significantly reduces the calculation and analysis time whilehaving acceptable accuracy. Model verification has been carried out in two parts (RC interfaces and RC pavements) in comparison with experimental results.