Bending Performance Of Prestressed Concrete Simple Supported Beams Under Different Grouting Compactness

The prestressed concrete structure have unparalleled advantages such as light structure,strong spanning capacity,delayed concrete cracking and so on.Since the20 s of the last century,it had made brilliant achievements in various engineering fields,especially in the bridge structure and large-span housing structure.However,in the actual prestressed construction,the insufficient grouting of prestressed duct is caused by the poor sealing,the duct blockage,the dry shrinkage of grouting material and other factors,and which will affect the cohesive force and coordination deformation between prestressed reinforcement and surrounding concrete.Furthermore,the corrosion and aging of the prestressed reinforcement is caused and the mechanical behavior of prestressed concrete structure is changed.Therefore,it is necessary to master the effect laws that the duct grouting compactness on the mechanical behavior of prestressed concrete structures.In this paper,according to the grading standard of the grouting compactness,8post-tensioned prestressed concrete beams are made with metal and plastic bellows under different duct grouting compactness,and the flexural performance tests are carried out respectively under the two-point concentrated load.The effect laws of duct forming materials and duct grouting compactness on the flexual performance of post-tensioned prestressed concrete simply supported beams are analyzed,and the current theoretical calculation methods are corrected.In order to further analyze the theoretical and experimental results,the full-scale finite element model of each test beams are established by finite element analysis software,and compared with the test results.In addition,under the action of uniform moving load,the dynamic response of post-tensioned prestressed concrete simply supported beams with metal and plastic bellows is analyzed with different duct grouting compactness by the finite element analysis method.The specific contents are as follows.(1)Taking the duct forming material and duct grouting compactness as influence factors,the experimental study on the flexural performance of the post-tensioned prestressed concrete beams is conducted,the characteristics and failure modes of the test beams under different working conditions are investigated,and the effect laws of duct grouting compactness and duct forming material on the strain,mid-span deflection and displacement ductility of concrete and non-prestressed reinforcement are analyzed.The results show that in terms of bearing capacity and displacementductility,when the duct forming materials are the same,the bearing capacity increases gradually with the increase of duct grouting compactness,while the displacement ductility coefficient decrease gradually.When the duct forming materials are different,the bearing capacity of post-tensioned prestressed concrete beam with metal bellows is higher than that of post-tensioned prestressed concrete beam with plastic bellows,and the bearing capacity increases by 5%.However,the ductility is lower,and the amplitude of displacement ductility coefficient decreases within 10%,and the higher the duct grouting compactness is,the lower the reduction amplitude is.(2)The crack development,mid-span deflection and bending stiffness degradation laws of beams are analysed and the grouting compactness coefficient is introduced.According to the theoretical calculation formula of the average crack spacing in the current code,the average crack spacing formulas for post-tensioned prestressed concrete beams under different duct grouting compactness is obtained through linear regression of experimental data.Based on the equivalent inertia moment method,the calculation method of the bending stiffness and the mid-span deflection of post-tensioned prestressed concrete beam are corrected,and the calculation method of the bending stiffness and deflection of the post-tensioned prestressed concrete beams under different duct grouting compactness are harmonized.(3)Considering the effect of duct forming material and duct grouting compactness on the post-tensioned prestressed concrete beams,the whole process nonlinear analysis of flexural performance test is conducted by finite element analysis method.The finite element analysis results are consistent with the experimental results,and the accuracy of the finite element model and the universality of the test conclusions are verified.(4)Under the uniform moving load,the dynamic response of post-tensioned prestressed concrete beams with metal and plastic bellows under different duct grouting compactness is analyzed by using finite element method.The results show that improving the duct grouting compactness of the post-tensioned prestressed concrete beam can reduce the dynamic deflection,delay concrete cracking and be more favorable to the force bearing of beam.