Research On Configuration And Mechanical Characteristics Of Main Cable Saddle Of Suspension Bridge With Spatial Cables

The suspension bridge with spatial cables has been widely applied.As its main cables are Three-dimensional,its spatial cable system is quite different from the plane cable system in many facets such as cable saddles.The suspension bridge with spatial cables usually applies two kinds of cable saddles——space-curve saddles and inclined plane saddles,which differ in structure and shape,but there is a lack of systematically comparative analysis of the above two saddles currently,and a fine researching in distribution of the saddle structure force and the lateral force between the saddle and its strand,which differ from the plane-cable saddles,is found nowhere in current researches.The different structure system also brings a certain influence in the secondary stress.In addition,the spatial cables system requires a linear transformation in construction from the finishing of saddle strands to the begining of lifting beams.The research is to analyze cable saddles of suspension bridge with spatial cables,the secondary stress and arrangement of the cross bracing in construction.The main content is as follows:1.In chapter one,the theoretical cable saddle shape of the suspension bridge with spatial cables is introduced firstly,then the fact that the inclined plane saddle is an approximation of the ideal cable saddle shape is pointed out.The calculation method of saddle designing parameters is presented and through comparing the designing parameters,the structure and the shape of the two types of saddles,a discussion over the selection of the saddle type is given.A conclusion that the inclined plane saddle could be the approximation of the space-curve saddle which differs from the space-curve saddle in structure and calculation method is drew,but the shapes of the two types saddle grooves projected onto the plane and facade are almost the same;in detailed structures,such as the center plane dip and the wire arrangement of the saddle grooves,the two types of the saddles have certain differences.2.Comparing the two types of cable saddles mechanically,the pressure and the overturning moment of inclined plane saddle on itself are illustrated firstly and the distribution of the lateral pressure between its strand and groove is demonstrated then,The centripetal force generated by main cable through the space-curve saddle and its relations with the radius of the transverse curve and the vertical curve is analyzed.A locality model is established to research in the distribution mode of the lateral pressure of the space-curve saddle and a discussion on the influence of different elements exerted over the lateral pressure.It concludes that the overturning moment generated by inclined plane saddle is related to the gravity of main cable;On condition that the gravity of the strand is ignored,no difference has been found between the inclined plane saddle and the plane saddle in the distribution of lateral pressure generated by the strand and the groove,which could apply the related theories of the plane saddle;The pressure and overturning moment generated by the space-curve saddle onto the groove could be calculated respectively through the vertical bending radius and the transverse bending radius.The lateral pressure between the strand and the groove is smaller on inner side while larger on outer side with a different distribution mode as well.The frictional coefficient between the steel wires excerpts a certain influence over the lateral pressure on both sides while that between the groove and the steel wires,very little influence.A strong effect on the lateral pressure caused by the transverse and the longitudinal force of the radial pressure is found.3.In Chapter three the secondary stress of the suspension bridge with spatial cables,mainly researching in the main-cable-related secondary stresses,such as the bending secondary stress of the strand at the outlet of the saddle during the erection of the strand and the rotational secondary stress of the cable clamp are analyzes.It concludes that there is little difference in the secondary stress between the spatial and the plane cable system;some secondary stresses in spatial cable system are larger while some are smaller,but in general,they are nearly the same.4.In chapter four,a data base of the lateral support helpful to the mathematical model analysis is established basing on the lateral support during the transformation of the shape,which is then verified by examples and leads to the main cable shape after setting the cross brace,the lateral support stress and the installation deflection angle of the clamp.It concludes that that the established model can preliminarily calculate the required number of transverse braces,which greatly affects the shape of main cables and the installation deflection angle of clamps;The force of transverse braces is related to the sequence of suspension beams.