| Nelson arch bridge refers to a new type of arch bridge with inclined boom instead of traditional vertical boom.In recent years,it has been widely used in high-speed railway construction due to its advantages of large rigidity,beautiful appearance and strong spanning ability.However,it is difficult to ensure the accuracy of arch rib alignment during the construction of this type of arch bridge,which requires strict construction management.Arch rib parameters,boom layout,transverse support and other design parameters have a great impact on the stability of the arch bridge,thus affecting the ultimate bearing capacity of the arch bridge.Therefore,it is necessary to study the influence of key design parameters on the stability of the arch bridge and establish a set of optimization design methods for the Nielsen type steel tube arch bridge.In this paper,the actual project of 128 m nelson type belay arch bridge is taken as the background.With the help of MIDAS/CIVIL finite element analysis software,the boom parameters,arch rib parameters and transverse support parameters are studied in depth.The main work and achievements are as follows:(1)The development of calculation theory and finite element analysis method for buckling stability analysis of arch bridge are briefly described.The classification of instability types is introduced.The form of arch bridge instability is given.The progress of theoretical analysis on buckling stability of arch Bridges is described.The finite element method for buckling stability of arch bridge is introduced.(2)The influence of boom parameters on buckling stability of concrete-filled steel tubular arch bridge is discussed.The stability and safety coefficients of arch Bridges with vertical boom,no cross diagonal boom and reticulated diagonal boom are calculated under different load conditions.Analysis of parallel boom decorate change Angle 45° ~ 90°,and the change regularity of structural buckling stability safety factor;The buckling stability coefficients of flexible suspenders,semi-rigid suspenders and rigid suspenders are calculated respectively.It is found that compared with vertical suspender,nelson type suspender is more advantageous to increase the structural stability of arch bridge,among which the reticulated inclined suspender is more advantageous than the non-crossed inclined suspender.The design of reasonable arrangement Angle can make full use of the stability advantage of inclined boom.The stiffness of lifting suspender is very significant to improve the stability of arch bridge.(3)The influence of arch rib parameters on buckling stability of concrete-filled steel tubular arch bridge is discussed.Respectively established in arch rib Angle 0 ° ~ 15 ° bridge three-dimensional finite element model,analysis the influence of parameters on the stability of the arch rib Angle.The influence of the change of arch rib inclination Angle on the stability of arch bridge is analyzed.When the stiffness of arch rib changes,the buckling stability coefficient of arch bridge is discussed.It is found that the inclination Angle of arch rib contributes significantly to the stability of arch bridge,and the setting of the inclination Angle of arch should be determined according to the actual project.Transverse support of arch rib can significantly improve the stability of arch bridge structure.The structural stability of arch bridge can be improved by increasing the stiffness of arch rib,but the lifting effect will be weakened gradually.(4)The influence of transverse support on the stability of concrete-filled steel tubular arch bridge is discussed.The influence of the position of transverse support on the buckling stability of arch bridge is discussed.The contribution of the number of transverse supports to the buckling stability of arch bridge is analyzed.Then,the contribution of "I","K","X" and "?" to the buckling stability of arch Bridges is discussed.It is found that the first-order stability coefficient of the structure is obviously improved when the transverse brace is arranged in the span rib from 3/8 to 1/4,which can be given priority in the project.The larger the number of transverse bracing is,the better it is.The best economic benefit can be achieved by selecting the right number of bracing.The influence of "K" type,"X" type and "?" type transverse brace on the structural stability of arch bridge is not different.It is not economical to strengthen the transverse stiffness to improve the buckling stability of arch bridge.(5)The optimization method of parameter design of nilsson steel tube concrete arch bridge is discussed.The optimization theory is introduced.Based on the optimization theory,the response surface analysis of the structural optimization parameters is carried out,and the nonlinear function relationship between the stability of the arch bridge and the design parameters is fitted.The numerical results of the optimization function are compared with the numerical simulation results to verify the correctness of the optimization method. |
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