Evaluation And Analysis Of Vertical Dynamic Deformation Of High Speed Railway Bridges Based On The Detection Data Of Track Inspection Vehicle

High speed railway construction is in the stage of all-round development in China.A large number of bridges have been adopted in the design of high speed railway to control the post-construction settlement of roadbed and save land,which forms the construction characteristics of high speed railway in China.At present,the evaluation and management of track regularity of high speed railway in China is mainly based on the data of track inspection vehicles.Mass data of rail inspection vehicles are discarded due to some objective reasons on the spot,and there is little research on the information of under rail structure and its relationship contained in the data of track inspection vehicle at present.To make full use of the measured track irregularity data of rail inspection vehicles,it is of great significance to excavate the structural characteristics and state information of the bridge and track slab in the measured data for the maintenance of high speed railway lines and bridges.To analyze the structural characteristics and state information of the bridge and slab under track in the measured data,a fast evaluation method for geometric state of simply supported beam bridges based on the detection data of rail inspection vehicle was proposed.Firstly,a multi-channel moving average filter was designed to identify and locate the simply supported beam bridge in high speed railway from the perspective of time-domain waveform.Then,the irregularity waveforms of simply supported beam bridges was separated,extracted and fitted by the statistical principle,and the periodic stiffness irregularities caused by the structural deformation of simply supported beam bridge(dynamic deformation of bridges)were extracted,and the geometric state of simply supported beam bridges was rapidly evaluated by box diagram.At last,the method was used to analyze the general characteristics of track irregularity and bridge deformation characteristics of simply supported beam bridges.The main conclusions are as follows:(1)The structural deformation of bridge is periodic irregularity in track irregularity,so the bridge deformation can be obtained from the characteristic waveform of periodic stiffness irregularity of bridge.Taking the inspection data of a unballasted track railway and ballast track railway in winter as an example,the simply supported beams of unballasted track railway appear downward deflection and the simply supported beams of ballast track railway appear upward arch.(2)The deformations of bridge downward deflection or upper arch are greatly influenced by seasonal factors.(3)Periodic fluctuation of mean wavelength of 5.00 m exists in vertical stiffness irregularity of simply supported beam bridges in unballasted track railway lines,which is close to the length of CRTS I track unit plate of 5.03 m.It is shown that the characteristic waveform is caused by the vertical stiffness irregularity of track plate.Taking ballasted track railway line and unballasted track railway line as examples,the evolution law of bridge dynamic deformation and its influencing factors were studied.Based on considering the main influencing factors,a multi-regression prediction model of bridge dynamic deformation was proposed and optimized model based on k-fold cross-validation principle.The main conclusions are as follows:(1)The dynamic deformation of the bridge in the unballasted track railway line is on the rise,and the downward deflection gradually changes into the upward arch.The dynamic deformation of bridge in ballasted track railway lines is mainly upper arch,and the arch value decreases as a whole.There are also seasonal periodic changes.The arch value in winter is larger than that in summer.The evolution law is consistent with that of track irregularity spectrum.(2)The main factors affecting the dynamic deformation of bridges are creep of concrete,the ambient temperature of bridges and the dynamic load of vehicles on bridges.In addition,the operating environment,service life,track types and construction methods of different railway lines and bridges are different,which will form some factors that are difficult to quantify.The specific state of railway line should be analyzed according to the measured irregularity data.To verify the proposed method of bridge dynamic deformation extraction,the mapping relationship between track dynamic irregularity and bridge dynamic deformation is analyzed by dynamic simulation.Through calculation,it is found that the waveforms of virtual track irregularity and bridge dynamic deformation are in good agreement.The amplitude of track irregularity increases by a constant value as a whole compared with the dynamic deformation of bridges,which is due to the influence of ballast,sleeper and fastener.the mid-span deformation value extracted from the virtual track irregularity is basically equal to the mid-span dynamic deformation value of the bridge.Therefore,the method of separating and extracting the bridge dynamic deformation based on the measured track irregularity data proposed in this paper has certain reliability.