Study On Operational Performance Evaluation Of 40+64+40m Prestressed Concrete Continuous Box Girder On Normal Speed Railway

After the revision of "Code for Verification of Railway Bridges" edition 04,the transverse stiffness of bridge span structure and other indicators have been modified,and the limit values of transverse acceleration and transverse displacement of rubber bearings in the midspan of simply supported beams have been given.However,with the development of national strength,the improvement of railway operation speed,the change of axle load of locomotive and rolling stock,the appearance of new bridge types,new structures and new technologies,some evaluation indexes are no longer suitable,among which the operational performance indexes of prestressed concrete continuous beams are still uncertain.Unlike the previous research methods based on a large number of measured data in Bridge Inspection Regulations,for such continuous beams without much test data,computer technology analysis of coupled vibration of vehicle-bridge system is a new way to determine the performance index of bridge operation.This way can simulate the different situations of vehicles and bridges and determine their limit state.Over the years,bridge engineering examples have proved that the existing vehicle-bridge analysis technology can well simulate the actual working state of bridges and vehicles.In order to meet the traffic safety and ride comfort,this paper deduces the vertical stiffness control index of the bridge based on the vehicle response limit state.Considering that creep is the inherent characteristic of prestressed concrete materials and exists in the life cycle of bridges,considering the most disadvantageous situation,it is considered that the residual creep,arch and support settlement after track laying of prestressed concrete continuous beams exist at the same time,and affect the irregularity of rail surface.On the premise of determining the initial deformation of the bridge deck and the settlement of the support,the elastic modulus of the bridge is changed.The stiffness of the bridge when the vehicle response reaches the limit value is determined by the dynamic response analysis of the vehicle-bridge.After considering a certain safety factor,the recommended value of the limit value of the bridge stiffness is put forward.The Midas/Civil bridge model of 40+64+40m three-span prestressed concrete continuous beam is established and the comprehensive test of the bridge is carried out.The vertical deflection in the midspan of the bridge under the real vehicle condition is obtained.Based on this,the vertical deflection-span ratio under the design live load is deduced and the rationality of the proposed limit value of bridge stiffness is verified.