Experimental Study On Size Effect On Shear Behavior Of Reinforced High-strength Concrete Corbel

As a support structure,the corbel is widely used in practical.For shear capacity of reinforced corbel,a large number of experiments and theory studies have been done by a large number of scholars and a great number of the calculation model of shear bearing capacity were also put forward by them.But there are little studies have been conducted on the size effect of reinforced concrete corbels,and whether those calculation models are suitable for different sizes of corbels haven't been approved.Due to the discontinuity of the structure of reinforced concrete corbel,the bear load of the corbel is also discontinuity.There is no unified analytical method for the shear capacity of the corbel at home and abroad due to the complex shear mechanism of the corbel.Further research for the shear capacity of the reinforced corbel are carried through the experiment and the analysis of existing research result,the applicability of existing calculation theory to different sizes is also discussed.In order to analyze the stress failure process,load-deflection deformation curve,collapse mechanics and the strain of concrete surface,longitudinal force steel bar and sheer stirrup of high strength concrete corbel,we completed the experimental study on sheer behavior of nine C60 grade high strength concrete double support corbel,the shear span radio and volume fraction of steel fiber of which are 0.2~0.4 and 0%~1.5%.The effects of parameters on shear capacity,crack morphology,normal crack load and oblique crack load of corbels with different sizes are mainly studied.According to the experimental phenomena and data,the results show that:(1)The effects of shear span ratio,longitudinal reinforcement ratio,stirrup reinforcement ratio and steel fiber ratio on shear performance of corbels were studied in this paper.The shear span ratio has a great influence on the cracking load,the crack morphology and shear bearing capacity of corbels.The reduction of the shear span ratio can significantly improve the cracking load and the bearing capacity of the corbel.Increasing the longitudinal reinforcement ratio and stirrup reinforcement ratio of corbels will improve the bearing capacity of the corbel,and the longitudinal reinforcement ratio and stirrup reinforcement ratio have little influence on the cracking load of the corbel;the increase of steel fiber radio will increase the cracking load,reduce the crack spacing and crack width,but have no significant impact on the failure load.(2)According to the analysis of shear bearing capacity of corbels of different series,the ratio of shear capacity of corbel to cross-section area of corbel is basically fixed,and the nominal shear strength of corbel of different sizes is basically the same while other factors remain unchanged.There is no obvious size effect on shear bearing capacity of small shear span ratio corbel.The maximum crack width of the corbel near failure is related to the size of the corbel.The maximum crack width of large size corbel is smaller than that of small size corbel.The ratio of the cracking load to the cross-section area of the corbel will decrease with the increase of the size of the corbel,that is,the cracking stress will decrease with the increase of the size of the corbel component.According to the size of the corbel,the fracture morphology is different when the corbel is damaged.The main inclined cracks are basically the same,but the number of normal cracks will increase with the increase of the size of the corbel.(3)Calculation formulas for shear bearing capacity of high-strength concrete corbels is offered according to the transfer mechanism of shear force in corbel Compared with the experimental results,it is proved that the formula is in good agreement with the experimental results.The shear bearing capacity of corbels is analyzed through the calculation models of triangular truss model,strut-and-tie model and shear friction theory in this paper.By comparing the test data with the calculation results,it can be seen that the calculation methods of triangular truss model and strut-and-tie model do not consider the influence of stirrups on shear bearing capacity,and have certain limitations.For the shear friction theory,the European code considers more comprehensively than the American code,and the ratio of calculation results to actual values is more stable and reasonable.The calculation of triangular truss model in the Chinese code is simpler,while the calculation of tie rod dry model and shear friction theory is slightly more complicated.