Research On Damage Mechanism Of Prestressed Concrete Box Girder Bridge To Over-high Truck Impact

In recent years,because of the traffic accident was more and more frequent,more and more structures have been hit by vehicle.Especially in the modern metropolis,the busy overpass and some other cross-line city bridges were often subjected to the impact of high vehicles,which results in vehicle and bridge damage.In order to reveal the dynamic response laws and damage mechanism of the prestressed concrete thin-walled box girder under the impact of vehicles.This paper uses both the computational dynamic theory and the LS-DYNA software to conduct the analysis work about the dynamic response and damage process of the prestressed concrete thin-walled box girder under a number of cases of vehicle impactThe main research work and achievements are as follows:(1)The LS-DYNA software has a complete function of geometric nonlinearity,material nonlinearity and contact nonlinearity.What kind of contact impact algorithm was used in the software and how to realize the contact nonlinearity in theory were explained in this paper.(2)The finite element model was established according to the test of the reinforced concrete T beam subject to the tank impact,which was made by Tsinghua University,and the simulation analysis was carried out.The analysis results were in good agreement with the experimental results,which proved that the LS-DYNA simulation of this kind of impact had a very high credibility.(3)The three-dimensional separation model of the superstructure of the fine prestressed box girder bridge was established by LS-DYNA software,and the connection of the reinforced bars and the concrete was treated by merging node method.Through the establishment of collision coupling model of vehicle and bridge superstructure,the damage process of bridge and truck and the overall displacement response of bridge were analyzed under a truck impact at a speed of 80km/h.It was indicated that when the car impacts the high mass bridge superstructure,the whole bridge damage was very little;the deformation of the car changed the impact form,which developed into a shearing impact from frontal impact.Under different speed conditions,the dynamic response of the bridge superstructure were analyzed and compared.The results showed that the larger the impact velocity was,the greater the impact force was;the larger the impact velocity was,the greater the displacement of impact zone was.And the increase of the displacement was nonlinear.(4)The dynamic responses of the thin-walled prestressed concrete box girder under the impact of the ultra high vehicle at different levels location,different height and different vehicle mass were discussed.The research showed that the shorter the distance between the impact position and the bridge support was,the higher the impact height and the bigger the weight of the vehicle,the more serious the bridge damage was.(5)The paper discusses the influence of the internal factors of the bridge structure on its dynamic response under the vehicle impact,which includes concrete strength,the ratio of the distribution bars and the stirrup ratio.Research result showed that: increasing the concrete strength,the distribution bar ratio and the stirrup ratio can effectively improve the anti-collision capability of the bridge.