Study On The Influence Of Corrugated Pipe Grouting Compactness On The Mechanical Properties Of Railway Prestressed Pier

Railway Prestressed Piers is a new type of structural pier which is first applied to railway bridges in China.The pier is connected by metal bellows and bonded prestressed tendons.It has the advantages of fast and convenient construction,stable performance,shortened construction period and green environmental protection.However,with the vigorous development of the engineering industry.The problem of structural concealment is placed in a prominent position.Therefore,the influence of duct grouting compactness on the mechanical properties of this type of pier is particularly critical.There is no complete detection method for the grouting compactness of prestressed ducts.This paper takes the new Heruo railway as the actual engineering background.Based on the above questions.Mainly carried out the following research:（1）According to the conventional bridge prestressed duct grouting compactness detection means.Combined with the difficulty of this kind of pier column test.From the three different detection methods of ultrasonic method,impact echo method and fiber grating method,the most feasible detection method with strong practicability,high test efficiency and wide development prospect is recommended.（2）The numerical simulation of axial compression of pier column model with six different defect rates of grouting density,7%,10%,13%,16%and full empty is carried out.The failure process and characteristics,load-displacement relationship,stress-strain relationship,ductility and energy dissipation analysis of pier columns are studied.The results show that,The final failure form of pier column is predictable ductile failure,and accompanied by two ends of the crushing cracks appear.As the defect rate increases.The ultimate load gradually decreases,the strain gradually increases,the ductility increases and the energy dissipation decreases.Therefore,Controlling the occurrence of defects has a certain improvement on the bearing capacity of pier columns.It has a certain influence on the protection of prestressed tendons from damage.（3）On the basis of numerical simulation research.Twenty small eccentric and five large eccentric compression pier models were established.The influence of defect rate and eccentricity on the characteristic value of concrete is analyzed.By comparing the simulation value and the theoretical calculation value.The recommended formula of concrete stress-strain relationship and normal section compression bearing capacity of axial and eccentric compression pier columns are obtained.On the basis of comparing the theoretical value and the corrected value results.Based on the simulation results of this paper.The correction coefficient of compressive bearing capacity of pier column affected by grouting compactness is proposed.The recommended formula for the axial compression bearing capacity of the normal section of the pier column satisfies:N_u修正=1.03N_u理论.The recommended formula of eccentric compression bearing capacity of normal section of pier column satisfies:N_u修正=1.1N_u理论.（4）Through the indoor loading test of 5 pier columns.The crack development trend and failure characteristics,load-displacement relationship,stress-strain relationship,ductility and energy dissipation law are further studied.It can verify the conclusions of point（2）.