| The strength of high-strength stirrup in reinforced concrete beams cannot be fully utilized due to the limitation of the diagonal crack width,and there are large differences between codes around the world regarding the values of design strength of high-strength stirrup.The code for design of concrete structures(GB 50010-2010)and the ACI 318-19 building code use the 45° truss model to consider the contribution of stirrup to the shear bearing capacity of reinforced concrete beams,but the actual inclination angle of critical diagonal cracks is usually less than 45° and the stirrup strain is difficult to be measured accurately by tests.Therefore,it is necessary to use the nonlinear finite element software ATENA to carry out a study on the effectiveness of stirrup in reinforced concrete beams,and the main work of this paper is as follows:Firstly,a nonlinear finite element analysis model of the shear property of reinforced concrete simply supported beams is established using ATENA software,and its correctness is verified using existing test results.The results show that the stresses in the stirrup traversed by critical diagonal cracks in the limit state of normal service,the first yield state of the stirrup and the limit state of bearing capacity can be extracted directly during the finite element analysis.Secondly,158 shear property test data of reinforced concrete simply supported beams with stirrups at home and abroad were collected and collated,based on which the nonlinear finite element analysis is performed to obtain the stirrup effectiveness factor of 1.47.From these,48 sets of matched pairs of specimens are selected to further analyze the reasonableness of the 45° truss model,and the results showed that the 45° truss model underestimated the shear load capacity of the stirrup.At the same time,a parametric analysis of the factors influencing the stirrup effectiveness factor is carried out.The results show that the stirrup effectiveness factor increases with the increase of concrete strength and stirrup yield strength,and decreases with the increase of stirrup spacing.Finally,for the value of high-strength stirrup in the limit state of normal service and the limit state of bearing capacity of reinforced concrete beams,a nonlinear finite element analysis is carried out using ATENA software,and the value of the design strength of high-strength stirrup is suggested.At the same time,the reasonableness of the minimum and maximum stirrup rate of reinforced concrete beams is analyzed. |
