Research On Structural System And Key Design Method Of Wide Span Curved Beam Low-Pylon Cable-Stayed Bridge

CURVILINEAR GIRDER CABLE-STAYED BRIDGE WITH LOW Pylon makes full use of the technical advantages of curvilinear beam bridge and cable-stayed bridge,and has the characteristics of beautiful structure.Although many curved Beam cable-stayed bridges with low pylon have been built in China,the span of the bridges is not large and the summary of technical achievements is not complete.Based on the structure of a 216 m main span and 44 m wide curved beam low pylon cable-stayed bridge,the paper analyzes the structural system,the mechanical performance of the components and the safety of the system,the key design technologies of this kind of bridge structure are summarized.The main research contents and conclusions are as follows:Firstly,the structural system of long-span and wide curved Beam cable-stayed Bridge with low pylon is studied.The main points of design are summarized for the Structural System Behavior of bridge during construction and operation,and the influence of different restraint systems on the structural safety is studied with parametric method.The results show that,under the influence of the curved shape of the main beam,the structure has significant bending-torsion coupling effect,which makes the deformation and force of the inner and outer beams different In addition,the coupling effect of bending and torsion can be produced by the beam arrangement and the spatial cable force,but this effect cancels out with the coupling effect of bending and Torsion,which can improve the force of the curved main beam,the results show that the space cable can improve the bending-torsion coupling effect ofthe curved beam and make it develop to a larger span,and the whole temperature of the operating structure and the vehicle load can produce a significant bending-torsion coupling effect,however,under the most disadvantageous load combination,the bearing will not be disengaged,so the bridge type is more difficult to disengage under the condition of reasonable tie-up,the most remarkable one is the overall temperature difference and the effect of the automobile load,but the consolidation system of the tower pier has a clear stress,can realize the good distribution of the internal force of the structure,can make full use of the cross-section performance,and has a better safety reserve,it is more suitable for curved low-pylon cable-stayed bridge.Secondly,the member performance of long-span and wide curved Beam cable-stayed Bridge with low pylon is studied.The maximum positive moment and the maximum negative moment of the main beam are selected respectively for the analysis of the spatial behavior,while the most unfavorable conditions are selected for the analysis of the spatial mechanical behavior of the frame columns.In order to reduce the effect of Shear lag effect,Short Flange and reasonable web space are set in the bridge.It is found that the shear lag coefficient of dead load is between 1.018 and1.169 by studying the shear lag coefficient of main girder,compared with the wide flange box girder structure,the short flange box girder of the bridge has less influence on the shear lag effect and the section utilization ratio is high,which proves the rationality of the scheme and proves that the box girder with this section can be used in the design of curved low-pylon cable-stayed bridge,good mechanical performance and economic benefit were obtained.In addition,the spatial analysis of the column shows that the column frame is affected by the Horizontal Force Component,and the column is deflected to the inner arc sideFinally,the system safety of long-span and wide curved Beam cable-stayed Bridge with low pylon is studied.The structural system safety is studied from three aspects: Elastic stability,elastic-plastic ultimate bearing capacity and structural safety under earthquake.The study shows that the safety factor of the first kind of instability is very high,all over 30,which indicates the stability and failure characteristics of the column as a compression member.Based on the analysis of ultimate bearing capacity of structural system with material and geometric nonlinearity,it is found that under different loading conditions,the pier top section,the middle column of SOTTA and the lower edge of the inner column are all after the main beam structure has yielded,it can be seen that four plastic hinges are produced at the same time,which shows thatthe stiffness distribution of the main beam structure is fairly uniform,and the buckling characteristic values are all in the range of 2.0 ~ 2.3,which is larger than the 2.0 value required by the code.In addition,in the structural safety analysis under earthquake,the natural vibration period of the bridge is close to that of other bridges of the same type,which is 5.75 s,and the vibration mode is longitudinal vibration of the beam body,the structural performance under p-1 and p-2 probability earthquake is checked,and the results show that the structure satisfies the seismic performance.Based on the research results of structural system,component performance and system safety,it can provide reference for the design theory and structure optimization of the similar curved Beam cable-stayed Bridge with low pylon.