| With the improvement of people’s aesthetics,cable-stayed bridge with allotypic tower and mixed cable plane has become popular in China.As a cable-supported girder structure,it combines the characteristics of ordinary girder bridge and cable-stayed bridge,and has a novel structure form and unique stress characteristics.At the same time,because of the steel itself has the characteristics of light weight and high strength,compared with the same type of concrete bridge is more likely to overturn.Therefore,it is of great significance to study the anti-overturning performance of such cable-supported girder structures.Based on a steel box girder cable-stayed bridge with allotypic tower and mixed cable plane,this paper uses MIDAS/Civil 2020 to establish a plate element model to research the anti-overturning performance of this kind of structure.The research contents and achievements are as follows:(1)By analyzing the principle and process of bridge overturning,and combining with the Chinese,British,American and Japanese codes,the overturning identification standard system composed of support reaction,torsion angle and anti-overturning safety factor is obtained.It is found that the plate shell model is more suitable for the study of anti-overturning performance.(2)According to British Specification(BS 5400)the transverse distribution frequency of wheel tracks,working conditions are set.The influence of different lateral action positions of loads on the anti-overturning performance is studied.The most unfavorable working condition is determined from four aspects,including girder deformation,support reaction,anti-overturning checking calculation and tower top offset.The results show that the extreme single lateral load is more likely to cause the bridge overturning.On this basis,the effects of overload,wind load and over or under tensioning of cable force on the anti-overturning performance are studied.The results show that bearing void is the beginning of bridge overturning,but it does not necessarily lead to overturning.A value of 2.5 for the anti-overturning safety factor is more reasonable for the judgment of cable-stayed bridge overturning.Overload can cause a sharp rise in the risk of bridge overturning;the influence of wind load is small,but compared with the different sides action with single lateral load,the same side action is more likely to cause overturning;the possibility of bridge overturning is positively correlated with the degree of cable force under uniformity when the cable force is over tensioned or under tensioned.(3)Combined with the novel structural form of the bridge,parametric analysis is carried out from structural system,support spacing,thickness of top and bottom plates and webs,thickness of diaphragms and cable plane spacing of central double cable plane,so as to research the influence of the above parameters on the anti-overturning performance,and provides some reference for the designers of similar bridge in the future.The results show that,as far as the structural system is concerned,it is reasonable to choose the semi floating system for the main arch and the rigid frame system for the main tower;increasing the support spacing can significantly improve the anti overturning performance;the thickness of each member of the main beam has little influence,so the corresponding member size should be selected reasonably according to the economic principle;the influence of the cable plane spacing is very small,almost negligible. |
