Theoretical Research On Camber Setting And Installation Error Of Long-span Steel Trussed Arch Bridges

With the developing of rapid transit railway construction, higher requirements of safetyand comfort of the bridges are needed for Passenger Dedicated Lines. That is to say, thebridges should have enough vertical stiffness, some lateral stiffness and smooth curve.Besides forming errors, camber setting and installation accuracy are also two key elements tothe shape of long-span steel trussed arch bridges. To make the shape and stress distribution ofthe completed bridges agree well with the corresponding design value, the paper researchedthe camber computation, the camber setting, the installation error compute and the installationerror control techniques according to the design procedures and construction technology ofthe long-span steel trussed arch bridge. The main research work covers the following aspects:(1) Equivalent process method in some special areas about finite element model ofcomputational camber.To solve the problem of the common beam elements, which can not directly consider thespecial structure of integral joint and diaphragm reinforced effect of chord member of steeltrussed arch bridge, a solide element model and several beam element models were erectedfor the common component parts. Then, frange plate of integral joint, high strength boltaddition with buttcover plate connection, diaphragm reinforced effect of chord member anddiagonal members and integral joint connection were computed with these models. Throughcomparing the calculation results, equivalent process method was obtained for solving thesespecial areas of steel trussed arch bridge. The result of the acceptance loading test ofDongjiang Bridge presents that the equivalent process method can get higher precision. So, amore reasonable camber will be obtained by the proposed method.(2) Study on fabrication camber setting of long-span steel truss bridgeBased on the finite element method, taken the relative camber between two adjacentnodes as displacement load, some computational formulas of member bar extension orcontraction were deduced for the frequently-used N type steel truss girder. The proposedmethod can be compiled conveniently and made a comparison table between the relativecamber and the length of member bars. So, the proposed method could avoid compute andadjust repeatedly, and a close to the theoretical camber curve could be designed easily by theproposed method. On that basis, a computational formula of the allowable value of relativecamber according to the fixed position boundary of driftpin, and some processing methods ofbolt hole were proposed for severe deviation closure members.(3) Installation error compute of member bars The fixed position of the chord member, vertical member and diagonal member werediscussed according to the construction technology. Then, the installation error was studiedunder cantilever construction of long-span stell trussed bridges. Through introducing fixedposition error concept, the computational equations were deduced by quincuncial fixedposition.On that basis, the installation error of chord member connection of Rongjiang Bridgewas obtained by the proposed equations. The calculated results present that: the line error offixed position has small influence on the cantilever end, and most of deviation of thecantilever end comes from angle error of fixed position; when two across corners bolt holesplay fixed position of the chord member role, the deviation is smallest.(4) The influence of cumulative installation error on finished bridgeBased on dimension chain theory and calculation method of fixed position error, theinstallation error line of cantilever construction and the extremum installation error of closurewere deduced. Then, the paper analysed the influence on the shape and stress of the stelltrussed bridge by the installation error. The installation error of construction of RongjiangBridge was researched by extremum method, which presents that: the cumulative installationerror has great influence on high precision closured, the shape and the stress of the bridge.(5) Research on installation error control technologyBased on dimension chain theory, the relationship between the diameter of bolt hole and thediameter of driftpin was deduced according the allowable installtion error value. The positiveinstallation error internodes by the negative installation error internodes distribution canminimize the influence on the shape and the stress of the bridge. According to constructiontechnology, the paper proposed some installation error control measures for the member barconnection, and researched a systematic adjust technology about closure error.