Study On Mechanical Properties Of The Super-span Suspension Bridge With CFRP Cables

In the new century, the security and durability of civil engineering structures, such asbridge structures and building structures are considered increasingly and structural materialsare put forward new challenges. For its good performances, such as light weight, highstrength, good corrosion resistance and fatigue resistance, Carbon Fiber Reinforced Polymer(CFRP) has caught the attention and interest of the civil engineering realm, and it has beenresearched and applied rapidly. Used as main cables of suspension Bridges, its advantages canbe exerted fully. On the one hand, the deadweight of main cables can be greatly reduced, thecarrying efficiency can be improved, thus the ultimate span of suspension bridges can beincreased; On the other hand, the problem of corrosion of steel main cables can be solved,especially under severe environment conditions, such as the ocean environment, steel maincables are very easy to corrosion; Again, as the weight of main cable sharply reduces, asmaller anchorage and tower can be used, so materials can be saved and construction isconvenient. Up to date, there is no precedent of suspension bridge with CFRP cable is built,related literature is very less, so a series of scientific research work around the theme ofsuspension bridge with CFRP cable has been carried out in this paper, combining with theNNSF of China-" Mechanical behavior analysis and optimization design method research ofcable bearing bridges with CFRP "(50908016). The main research results and conclusions aresummarized as follows:1、Calculating of completed state of suspension bridge with CFRP cableAs the basis of accurate analysis of static and dynamic performance of suspension bridges,the method of calculating the line shape and internal force of main cables is studiedsystematically in this paper. The calculation formulas of the line shape and internal force ofthe single cable and the segmental catenary cable are established respectively. Iterationmethod of the design parameter of the cables is put forward and a corresponding calculatingprogram is compiled.The calculation method of tangent point coordinates of main cable and saddle groove isstudied, the calculation formulas of interactive forces between main and saddle groove and the unstressed length of the main cable inside the saddle groove are deduced. Then the designrequirements of CFRP main cable saddle are discussed.2、Static performances analysis of super-span suspension bridge with CFRP cableThe analytic calculation formulas of the ultimate span, carrying efficiency，main cable areaand deadweight stress of suspension bridges are deduced independently. The aboveparameters of two kinds of cable suspension bridges are calculated and compared. It indicatesthat CFRP cables suspension bridges have more advantages compared with steel cablessuspension bridges.The2000m-span,3000m-span suspension bridges with CFRP cables and steel cables and5000m-span suspension bridge with CFRP cables are designed deploringly. The staticperformances of the two kinds of main cables suspension bridges under the action of deadload, vehicle load and temperature are analyzed and compared using of the finite-elementmethod. Some important conclusions are obtained, which can provide scientific proofs fordesign.3、Dynamic performance analysis of super-span suspension bridge with CFRP cableBased on the analytic estimation formulas of fundamental frequency of suspension bridges,the natural vibration characteristics of CFRP cable suspension bridge is studied qualitatively,the results show that frequency ratio of torsional and bending of CFRP cable suspensionbridge is greater than the corresponding values of steel cable suspension bridge, which is goodfor improving the wind stability.Based on the models established for aforementioned static analysis, dynamic characteristicsof super-span CFRP cable suspension bridge and steel cable suspension bridge are analyzedand compared using of the finite element method. The general rules of dynamiccharacteristics of the super-span CFRP cable suspension bridge is summarized; Through theanalysis of influence of several main design parameters on the dynamic characteristics of theCFRP cable suspension bridge, the measures for improving the aerodynamic stability ofCFRP cable suspension bridge are put forward, which provides a theoretical basis forstructure optimization design.4、The study on aerostatic stability of suspension bridges with CFRP Cables According to the research techniques and the control equations of fluid mechanics, thenumerical simulation method of the aerodynamic characteristics of the stiffening girdersection is established. The static three component force coefficients are extracted respectivelyusing the FEA and the FLUENT software; Both are in good agreement, which indicates thatthe calculation results are credible. The aerodynamic characteristics of several kinds of maingirder section with different aerodynamic measures of edge tuyere are researched for the firsttime using CFD method. A reasonable cross section type is suggested in this paper, whichprovides a scientific basis for optimization design of the stiffening girder section.The stability and deformation characteristics of the two kinds of cable suspension bridgeunder calm wind load are analyzed and compared for the first time using bridge structurethree dimensional nonlinear aerostatic analysis methods. Analysis results show aerostaticinstability critical wind speeds of the CFRP cable suspension bridge is a little smaller thanthat of steel cable, which is consistent with calculation results from the empirical formula.The effects of rise-span ratio, constraint condition of stiffening girder and cable system，etcon the aerostatic stability of CFRP cable suspension bridge are analyzed for the first time,accordingly measures of improving wind resistance stability CFRP cable suspension bridgeare put forward.5、Mechanics Analysis of the adhesive Anchorage with CFRPThe analytic calculation method of the ultimate capacity of straight pipe anchorage isproposed. A kind of straight pipe inner cone anchorage is designed. Finite element analysismethod of CFRP adhesive anchor is established and the Loading process of it is analyzed bythis method.The effect of elastic modulus, thickness of the adhesive colloid, anchorage length andinner cone angle on the mechanics performance of anchorage are analyzed for the first time,which will provide a scientific basis for optimization of CFRP anchor.