| In recent years,the overturning accidents of single-pier bridges have occurred frequently in China,which has caused great loss of people's lives and property and bad social impact.It has attracted the attention of bridge engineering and academia,and has carried out a lot of analysis and Research on the process and mechanism of overturning damage of bridges.In 2018,the Ministry of Transportation promulgated and implemented the new industry standard "Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts"(JTG 3362-2018),in which the lateral anti-overturning stability coefficients of integral simply supported beam and continuous beam bridges are clearly stipulated.At present,most of the research results and the calculation theories and methods of the above specifications are mainly based on the assumption that rigid body rotation occurs in the superstructure.However,the calculation results show that in actual bridge overturning accidents,the anti-overturning stability coefficients of some bridges meet the requirements of the specifications,but under the eccentric load of heavy-duty vehicles,Overturning and destruction accidents still occur.Although vehicle overloading is the direct cause of accidents,this phenomenon should be paid attention to.The mechanism of overturning of bridges still needs to be further studied and discussed.For this reason,this paper combines the overturning accident cases of the south exit ramp bridge of Heyuan City of Guangdong-Jiangxi Expressway,and does the following work:Based on the current specifications,a grillage model is established by using Midas civil software.The bearing reaction,bearing rotation angle,anti-overturning stability factor and critical radius of overturning of the above-mentioned bridges are calculated.The calculation results show that the bearing rotation angle of the bridge is less than 0.03 rad,and the anti-overturning stability factor is applied to the highway-I Lane load,the load of dense vehicle group and the overturning critical radius.The actual overload conditions are 3.2,1.8 and 1.5 respectively,which meet the requirements of the code.The critical radius of overturning is 516.1 m,which is larger than the actual radius of the bridge 220 M.The geometric structure of the bridge meets the requirements of lateral stability.The ABAQUS software is used to establish a solid model to simulate and analyze the reaction of the support,the displacement of the support,the deformation of the beam and the overturning process of the bridge under heavy vehicle loads,and the results are compared with those based on the current code.The numerical simulation results show that during the overturning process of box girder,there are some phenomena,such as uneven deformation of box girder,extrusion of middle pier support,contact between middle pier and upper box girder,compression failure of outer support at beam end and void of inner support,which are in good agreement with the actual overturning accident of bridge.At the same time,in the process of bridge failure,the geometric non-linearity effect is very significant,which is manifested in the redistribution of vertical reaction force,the deformation and rotation angle of box girder and the non-linear change of pier top horizontal thrust in the process of overturning.It shows that the influence of geometric non-linearity effect can not be ignored in the analysis of such accidents.The above research shows that there are still some limitations in the analysis and evaluation of the lateral anti-overturning stability of Bridges Based on the calculation methods of current codes,and the requirement of anti-overturning stability coefficient is not enough to ensure the lateral stability of bridges.The influence of non-linear effect needs to be paid enough attention.It is expected that the research contents and methods in this paper can provide reference for the analysis of anti-overturning stability of new and existing bridges. |
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