| Retard-bonded prestressed concrete system is a new type of prestressed system developed on the basis of unbonded and bonded prestressed system.This technology eliminates the reserved duct and grouting process of the bonded prestressed system,overcomes the defect that there is no bonding between the prestressed reinforcement and concrete of the unbonded prestressed system,and the problem that the anchorage is easy to fatigue failure in the later stage,and has good mechanical properties.It has been applied in many projects at home and abroad.Scholars at home and abroad have done a lot of research on the retard-bonded prestressed technology,but there is no systematic research on the bond performance and influencing factors of the retard-bonded prestressed steel strand,and the relevant finite element analysis is relatively few,which affects the application and development of the retard-bonded prestressed technology to a certain extent.Therefore,this paper carried out experimental research on the bonding performance between retard-bonded prestressed steel strand and concrete,analyzed the bonding performance between retard-bonded prestressed steel strand and concrete,then used finite element analysis software to analyze the factors affecting the bonding performance of retard-bonded prestressed steel strand.The completed work and main results are as follows:(1)The bond stress-slip curves and bond failure modes of the retard-bonded steel drawing members and the pure prestressed steel strand drawing members were obtained through experiments.The bond failure mode of retard-bonded prestressed steel is the shear failure of adhesive transverse ribs,and the failure mode of pure prestressed steel strand is the pull-out failure of steel strand.The bond stress-slip curves of the two pullout components are quite different.The bond stress-slip curve of the retard-bonded steel drawing member is a curve with a single peak point,while the bond stress-slip curve of the pure steel strand has a long elastic section,and there is no decline section of the curve after reaching the limit state.(2)On the basis of the experimental study,the drawing test of the retard-bonded steel strand was simulated by using the finite element software,and the test results agree well with the simulation results.According to the finite element results,the force transmission mechanism of the bond between retard-bonded steel strand and concrete is analyzed.(3)Parameter analysis was carried out on the factors affecting the bonding performance of retard-bonded reinforcement.The influence law of rib shape parameters of retard-bonded steel strand on the bonding performance of retard-bonded steel strand is obtained.Through analysis,it is found that the range of rib width and rib spacing with better bonding performance is within the range specified in the specification,which verifies the rationality of the specification.According to the finite element simulation results,the ratio of rib width and rib spacing with better bonding performance is 0.5.The effects of adhesive material properties,concrete strength,lateral constraint conditions,bond length,concrete cover thickness and other related parameters on the bond performance of retard-bonded steel strands were also analyzed by finite element simulation.The influence law and degree of these factors on the bond performance of retard-bonded steel strands were obtained.For the parameters with obvious change law,the mathematical expression between these parameters and bond strength was given. |
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