Research On The Influence Of Different Parameters On The Impact Coefficient Of High-speed Railway Simply Supported Bridge

The simply supported bridge is widely used in high speed railway bridges.The speed of the high-speed railway makes the problem of the interaction between the train and the bridge more and more serious.The impact coefficient is used as an important norm to measure the dynamic performance of the bridge.The calculation of the impact coefficient of the simply supported bridge in the standard for design of high-speed railway bridge is a single function of the span.But the number of factors influencing the impact coefficient are numerous.This paper summarizes the domestic and foreign research on the impact coefficient and the calculation method in the standard.Modeling the multi-rigid vehicle model.After making the hypothesis of neglecting of the relative displacement between the track and the bridge,and neglecting the elastic deformation of the track plate,the bridge structure model is established,and the modal analysis is carried out by using the modal synthesis method.The kinetic equation of vehicle-bridge coupled vibration is established,and the PARK method for solving this dynamic equation is adopted.Taking the simply supported beam bridge of 32 m high speed railway as the research object.A finite element model of four different cross-section 32 m simply supported beam is established in ANSYS and then introduce the model through the ANSYS-UM interface into the multi-body dynamics analysis software UM.And the vehicle model established in UM either.Combined with the vehicle model established in UM to analyze the dynamic response of axle and bridge.The influence of four factors such as driving speed,track irregularity,train marshalling and single-lane driving on the impact coefficient of simply supported beam bridge are studied respectively.In the standard of highway bridge design,the impact coefficient is a function of the fundamental frequency,and some scholars have found that the cross-sectional form for the impact of the impact of the coefficient is more obvious,to calculate the impact coefficient basing a single span or base frequency is not accurate enough.So for the railway bridge,How does the cross section form affect the impact factor.The ANSYS and UM co-simulation techniques are used to study the influence of the cross-section on the impact coefficient design in the same conditions,and sensitivity of impact coefficient to cross section in different vehicle speeds.It is concluded that the impact coefficient does not increase with the increase of the speed of the vehicle,but the peak will appear at the resonant speed.The influence of the track irregularity on the impact coefficient of the bridge is limited.The influence of the single train on the impact coefficient is different from the marshalling trains,and the influence on impact coefficient is not much different from different marshalling trains.Only the peak at some resonance speed is different.When train moving on the single-lane,the impact coefficient of the no-load side is larger than that of the traveling side,the impact coefficient of the bottom surface of bridge is larger than that of the top surface,the size of value of the impact coefficient of the bridge is independent of the dynamic displacement.The cross-sectional type is one of the factors that affect the impact coefficient of the bridge.The difference of the impact coefficient caused by the different cross-section is more than 2 times.The sensitivity of the same train to different sections is not the same under the different pace and cross-section type.This paper defines a sensitivity interval to describe this difference,Beside the design speed and some unique speed,the impact coefficient of the simply supported beam bridge is not sensitive to the cross section.The impact coefficient of the simply supported beam is sensitive to the cross section in most velocity intervals,and very sensitive to crosssection type under the resonance velocity.The research of this paper has engineering significance for the design of high-speed railway simply supported bridge,which also has certain theoretical significance for vehicle-bridge coupling analysis.