Research On The Design Of Composite Pipe Restraint Structure And The Calculation Method Of Its Key Parts

Pipeline restraint structure in water tunnel is an important structure to ensure the safe operation of oil and gas pipeline,prevent oil and gas leakage caused by pipeline floating damage,and then avoid oil and gas combustion,explosion and other consequences threatening tunnel safety.At present,the oil and gas pipeline uses the concrete buttress to set the pipe clamp,anchor bolts and other restraint structures to prevent the pipeline from floating,and these components are usually made of steel members.Whether it is ordinary carbon steel or stainless steel,in the humid environment of water tunnel,all components are corroded,which threatens the safety of pipeline and tunnel..Therefore,this Paper proposes the use of glass fiber reinforced polymer(GFRP)to make the pipe restraint structure to overcome the defects of steel members easy to rust.The research is as follows:(1)In this Paper,a new constraint structure is proposed for the material characteristics of GFRP anisotropy and the stress characteristics of the pipe confined structure in the tunnel,and the key Parts of the new structure are analyzed.(2)Experimental study on bolt connection in key parts,results to show:the short nut length will reduce the bearing capacity of GFRP bolt connection;when the bolt end distance is less than 3.0 times of the bolt diameter,the connection is prone to tear or split;when the bolt edge distance is less than 3.0 times of the bolt diameter,the plate is prone to tensile failure;increasing the bolt end distance or the bolt distance can reduce the bearing capacity of GFRP bolt connection It can increase the deformation and bearing capacity of the connection;when using multiple bolts,it can improve the stiffness and bearing capacity of the connection,but it is more prone to tensile failure than a single bolt;compared with steel bolts,GFRP bolts may shear in the bearing process,so the bolt diameter can be increased appropriately.(3)This Paper introduces the calculation idea of bolt connection strength in detail.Firstly,three calculation methods of bolt load distribution are analyzed and compared.Then,the realization process of strength envelope method and characteristic curve method in bolt connection strength prediction is described and illustrated in detail.It is concluded that the strain electrical measurement method is not suitable for the calculation of screw load distribution,the difference between the mechanical formula calculation and the finite element numerical solution is small,and the formula method can simulate the actual distribution;the accuracy of the two strength prediction methods can meet the engineering needs,but the failure load predicted by the strength envelope method is more dangerous,and the failure load predicted by the characteristic curve method is more conservative.(4)Experimental study on anchorage of GFRP bars in key parts,results to show :with the increase of diameter,the average bond strength decreases;with the increase of anchorage length,the bond strength decreases,but the total load value increases;the average bond strength of sandblasted bars increases by about 18%,and it is suggested to sandblast the GFRP bars in use;improving the concrete strength can also improve the bond strength.Based on the requirements of domestic and foreign codes and applications,the calculation methods of bond strength and anchorage length of GFRP bonded bars are proposed.