Structural System And Performance Analysis Of Cable-stayed Bridges With Different Ratio Of Side-span To Mid-span

When the ratio of side span to middle span is relatively small,the cable-stayed bridge is extremely asymmetric,but in some conditional projects,the structure is a form of structure that can be adapted to the needs.Therefore,it is of great theoretical and practical significance to study its different structural systems and mechanical properties.In this paper,cable-stayed bridges with three structural systems of self-anchored cable-stayed bridge(i.e.conventional cable-stayed bridge),partially earth-anchored cable-stayed bridge with separation of girder and anchorage and partially earth-anchored cable-stayed bridge with consolidation of girder and anchorage are studied.The suitable range of the ratio of side-span to middle-span is studied,and the influence of the ratio of side-span to middle-span change and girder type change on structural mechanical properties is analyzed.The main work and conclusions of the paper are summarized as follows:(1)By analyzing the static equilibrium relationship between the girder and tower in cablestayed bridges with various structural forms of bridge formation stage and construction stage is analyzed,the most unfavorable stress stage and position are determined.(2)From the point of view of the stress safety of the girder and tower in the formation stage and construction stage,a rapid mechanical analysis method which can be calculated by hand is introduced,which is used to estimate the suitable range of the ratio of side-span to middle-span of various structural cable-stayed bridges.(3)The suitable range of the ratio of side-span to middle-span of various structural cablestayed bridges is obtained through analyzing the structural mechanical properties in the formation stage and construction stage,and the influence of the ratio of side-span to middlespan change and girder type change on the static characteristics of the structure is determined.The result shows that self-anchored cable-stayed bridge meets the stress requirements in the range of 0.275～0.5,and the influence of the ratio of side-span to middle-span on static characteristics of structures is complicated;the partially earth-anchored cable-stayed bridge with separation or consolidation of girder and anchorage meets the stress requirements in the range of 0.15～0.4,and when the ratio of side-span to middle-span is about 0.275,part of the structure’s critical static response is minimal;the steel box girder scheme is usually suitable for the cable-stayed bridges with three structural systems.(4)The variation of longitudinal displacement and internal force caused by temperature effect of the partially earth-anchored cable-stayed bridge is analyzed from the analysis.It is found that the longitudinal displacement and internal force of the two systems decrease approximately with the decrease of the ratio of side-span to middle-span under the overall warming.(5)The mechanical properties of the self-anchored cable-stayed bridge in the construction stage after changing the free cantilever erection method are obtained through analysis.The result shows that the main beam bending moment and the maximum displacement at the top of the tower in the construction stage are improved through the method of assembling all beam sections of side span on the support and then symmetrically tensioning cables with the middle span(Scheme 1)and the method of the side span over the middle span of a segment cantilever assembling from the loading section(Scheme 2).But the displacement of the tower facing the side-span increased.And the compressive stress at the bottom of the tower of scheme 1decreases,the stability of the bridge in the construction stage is significantly enhanced.