| With the process of urbanization in China,viaducts have been built all over the country to relieve traffic pressure.However,in recent years,the overall instability accidents of domestic viaducts have occurred frequently,which has brought serious negative impacts to the whole society.Although these accident bridges are mostly caused by serious overload and concentrated partial load of vehicles,some scholars should not use overloaded vehicles as load access standards for checking calculations,but should improve the stability of the bridge at the design stage.At present,some scholars have idealized the superstructure as a rigid body when checking the anti-overturning of the bridge,thus overestimating the bearing capacity of the bridge.Therefore,based on the current bridge design code,this paper divides the process of bridge instability into two different states,and treats the superstructure of the bridge as a deformation body for anti-overturning checking.The research results of this paper are as follows:(1)Taking the overall bridge instability accidents occurred in the past 10 years as examples,we summarize the common features and damage patterns of these accident bridges,analyze the process of overall instability of bridges,It is concluded that the essence of overturning is that the superstructure of the bridge rotates first and then slides.,which provides a theoretical basis for the study of the anti-overturning stability of bridges.(2)In this paper,the relevant specifications of bridge stability in China are systematically reviewed.A three-span viaduct in Sanmenxia is established by Midas finite element software,and the anti-overturning calculation is carried out by Civil Designer.The advantages and disadvantages of ’ overturning axis method ’ and ’ failure bearing method ’ in calculating the anti-overturning coefficient of bridges are analyzed.On this basis,an improved algorithm of load combination is put forward,in which the parameters such as temperature,centrifugal force and static wind load should be considered when checking the overturning resistance of curved girder bridges,so that the calculation results are more in line with the actual requirements.Finally,based on the improved algorithm,the effects of bridge curvature radius,support arrangement,support spacing and side-to-middle span ratio on the overturning stability of the bridge are calculated and analyzed.(3)Vehicle overload is a key factor affecting the service life of the bridge.The research shows that the overall instability accidents of the bridge will still occur when the antioverturning calculation is carried out with 1.4 times the lane load.Therefore,this paper takes the fleet of 550 k N standard vehicles as the vehicle load,analyzes the single vehicle limit load of the viaduct under different curvature radii when single vehicle,double vehicles,three vehicles and four vehicles cross the bridge,and finally puts forward the relevant countermeasures to prevent vehicle overload.(4)In order to prevent the overall instability and failure of the bridge,on the one hand,’hard ’ measures should be taken,which can be strengthened by adding pier columns,adding capping beams,and increasing the cross-sectional area of the pier.On the other hand,’ soft ’measures can also be taken to strictly monitor vehicle overload behavior by applying new technologies and new schemes of bridge monitoring.(5)Taking the actual project as an example,the finite element model is established for anti-overturning checking.Combined with its own construction conditions,the method of adding steel cap beam and bearing to the middle pier is selected to improve the stability of the bridge,and the anti-overturning checking of the bridge after reinforcement is carried out.Finally,it is concluded that the method and theory can also be reinforced for different similar ramp bridges and elevated road facilities. |
