Parameter Study Of High-speed Railway Bridge Design Based On Interaction Among Train,Pathway And Bridge

China has made remarkable achievements in the construction of high-speed railway(HSR),of which the operating mileage occupies above half of the total mileage in the world.The ‘Four vertical Four horizontal' HSR network has already been developed,while the ‘Eight vertical Eight horizontal' HSR network is under construction.Up to 2025,the operating mileage of railway network will reach 175,000 km,in which the operating mileage of HSR will raise to 38,000 km.Regarding to the type of infrastructure,bridges take a large proportion in China's HSR.On one hand,over 90% of the high-speed bridges belong to the simply supported girder bridge of frequently-used span,on the other hand,because of complicated terrain and geological conditions as well as changeable environment,a number of long-span bridge are constructed to cross existing structures such as road,railway,big rivers and valley.Recent years have witnessed the significant progress of both the span bridge and long-span complex bridge frequently-used in China's HSR,with numerous engineering experience and scientific payoffs being accumulated.Yet,the present research is still not systematic enough.Moreover,plenty of bridges with larger spans are needed for the on-going construction of HSR,thus some new technical problems have to be solved urgently.Based on preceding statement,it is of importance to sort out and analyze the existing research about the construction of HRS bridges,and conduct systematical study on the design parameter and range of application.Then,the specific research will be conducted to deal with the technical challenges occurring in the design and operation stages,in order to promote the development of China's HSR.Based on the train-track-bridge coupled dynamics theory,the thesis focuses on the study on key design parameters of frequently-used span and large-span bridge in HSR,of which the main works and achievements are as follows:(1)Analysis standard for train-track-bridge coupled dynamics in HSRIn general,the HSR bridges demonstrates high dynamic performance according to the survey on the track status,the test on the dynamic performance of bridges as well as the analysis on the key design parameters of bridges.Yet,there still exists various defects in the HSR bridges,e.g.,remnant creeping and deformation of frequently-used span bridge,degraded track status on the large-span complex bridge suffered from temperature and creeping.As a consequence,the static deformation is usually significant,which affects the ride comfort of the bridge.For this purpose,this thesis aims to account for various kinds of environmental factors as well as status during long-term service,and then sort out the loading conditions and environmental effects based on the probability of occurrence,action time as well as the influence on the track geometry.Thereafter,the hierarchical control standard for analyzing the vehicle-bridge coupled dynamics in HSR will be put forward.(2)Optimization on the model of track-bridge coupled dynamicsIn the model of vehicle-track-bridge coupled system,the thesis improved and optimized track-bridge model,in which the rail,railpad as well as fastening were treated as the rail sub-system,the rail was simplified Euler beam supported by discrete springs and dampers,the effect of under-rail structure on the rail was specified as forced displacement and forced speed,while effect of rail subsystem on the under-rail structure was simplified as external load.In such a way,the calculating accuracy is rarely affected by the length of the rail,so that the partial vibration of the rail can be simulated in a better way.Meanwhile,the modeling of the bridge structural can be simplified,and effects such as degraded rail joints,welds and earthquake can be represented properly.(3)Settlement control standard of frequently-used span simple supported girder bridge in HSRAccounting for the aspects of vehicle dynamic performance,static performance of track structure,track stability,loading features of indeterminate bridge structure,this thesis put forward the grading evaluation suggestion of frequently-use span bridge difference for HSR by considering the incidence of settlement and creeping coupling effect on response of vehicle,track and bridge.(4)Static deformation control standard of HSR long-span bridgeBased on the engineering background of a main span 445 m deck type reinforced concrete arch bridge,the survey and analysis indicated that the static deformation of long-span complex bridge suffered from environmental factors is more significant than the dynamic deformation caused by the passage of the train.Thus,the static deformation should be limited in order to guarantee the operation safety and comfort during long-term service.Meanwhile,exaggerated maintenance load must be avoided.The results suggested to adopt the chord measuring method rather than deflection span ratio as the control standard of bridge deformation.In addition,the static deformation limit suggestion of 4mm/40 m bridge floor was put forward based on the studied engineering practice.(5)Key parameter of 40 m simply supported girder design for 400km/h HSRThe analysis on the vehicle-track-bridge coupled dynamics for 40 m simply supported girder bridge under 400km/h demonstrated good dynamic performance of bridge structure.In order to guarantee the operation safety and comfort during vehicles passing-by,it would better to improve the irregularity level on the bridge and reduce the remnant creeping after laying the railway,the creep of the 40 m simply supported girder bridge should be below 4mm.