Study On The Stress Of Main Cable Under The Railway Suspension Bridge Long Cable Clamp And The Sliding Resistance Bearing Capacity Of Cable Clamp

Long span railway suspension bridges have heavy dead load and live load,require high structure stiffness,so their main cable size will be designed to be very big.The main cable diameter of Wufengshan Yangtze River bridge under construction is nearly 1.3 meters when fastened.The big and elliptical main cable section will cause complex stress relationship.The end hanger force is usually big,and inclination angle is the biggest,so the sliding resistance problem of cable clamps in this area is the most prominent.Chosing long cable clamps to arrange more high strength screws to improve the sliding resistance bearing capacity of cable clamps is commonly usesd in the design process,which caused the mechanical relationship of main cable and cable clamp system is seriously influenced by the main cable sag.Aiming at the above problems,the thesis has carried on the related research.The main contents,methods and contributions are as follows:Using the heterogeneous theory,basing on the macroscopic mechanical properties of the main cable and the cable clamp fastening system,aiming at stress distribution in the main cable section,the non-linear relationship between steel wires and void of the main cable was simplified by using the three dimensional anisotropic material to take the place of the main cable system in the research.The stress-strain relationship of three dimensional anisotropic equivalent material was fit by building the ANSYS finite element entity model of the main cable and the cable clamp fastening system and combining measured data and finite element analysis.The material was proved to be of general eligibility in the research of the main cable and the cable clamp fastening system.The equivalent material was used to research the main cable mechanical behavior under the long cable clamp influenced by sag.The surface and interal stress of the main cable and the stress regularities of distribution influenced by different cable clamp band of halves type were explored.The elliptical main cable effect was especially analyzed.The multiscale finite element model was built to simulate the fastening and loading process,to explore the sliding resistance bearing capacity of cable clamp overal considered the cable sag,the different cable clamp band structure of halves type,the hanger force,the local slip of the main cable and the cable clamp contact area,and the main cable section change at the end of the cable clamp,and to evaluate the sliding resistance bearing capacity of cable clamp during operation process.High strength screws relaxation regularity and the sliding resistance ultimate bearing capacity during the operation process of long and short cable clamps were explored by different fastening methods of high strength screws under considering of cable sag and hanger force.The calculation and analysis results show that structural distortion is identical to the experimental result and stress result is nearly true when using the three dimensional anisotropic material to equivalently simulate the main cable system.The distortion curve is identical to another experimental data under sharply different main cable section when using the finite element method to simulate the process of the main cable fastening,which proves the material is of general eligibility in the research of the main cable and the cable clamp fastening process.The radial stress and the tangential stress in the main cable section show the distribution of circle under the fastening effect of the cable clamps.The stress is less at the center section while larger at the main cable surface.There are obvious stress concentration and secondary stress at the end of the cable clamp,and the stress contour line is related to the relative dimension of the main cable diameter and the cable clamp thickness.The cable sag and ellipicity will affect the distribution regularities of stress in the main cable section.The secondary stress of the main cable surface is related to the main cable sag and transferring way of cable clamp force.The secondary stress is distributed at the end of the cable clamp in the range of 12cm.The sliding resistance bearing capacity of the cable clamp calculated by integrating the friction stress on the area of the contact surface is bigger than the cable clamp sliding force when enlarging the load until the cable clamp sliding.This shows that hanger force and the local slip of the main cable and the cable clamp contact are harmful to the sliding resistance performance especially for cable clamp of left and right halves type.The sliding resistance bearing capacity of the cable clamp during construction and operation process is influenced by the cable clamp length,cable clamp band of halves type,ellipicity of the main cable,and fastening project of the high strength screws when considering the main cable sag.Shorter cable clamp,more fastening stages,rounder main cable section,and fastening the high strength screws from the middle of the cable clamp are good for improving the sliding resistance bearing capacity.In the process of installing the stiffening girder,adding the tension of the high strength screws is needed to ensure the sliding resistance bearing capacity of the long cable clamp near the cable tower.During the operation process,the sliding resistance safety coefficient of the long cable clamp is less than 3.Fastening the high strength screws at the designated tension when installing and adding the tension at finished bridge state,the short cable clamp at the middle span can ensure the sliding resistance bearing capacity at construction and operation process.