Seismic Performance Of Round End Pier In Passenger Railway

Because of the synthesis advantages in high speed,safety,punctuality, convenience,comfortability,passenger railway has been widely developed all over the world,and a new peak to built passenger railway is being formed.Current executed Seismic Design Code for Railway in fortification criteria,earthquake action calculated method,earthquake design method and seismic constructional measures of bridge seismic has been updated on the basis of old code,but the new code is made for common railway bridge and can not be directly used in passenger railway bridge design, which is determined by the factors characterizing the design of passenger railway bridge of big mass,big rigidity,ductile design and high durability.Although passenger railway design had been researched for many years,as well as we had gained lots of successful experience,systemic theory and test research on the key problems of passenger railway seismic fortification criteria,performance aims,design method,analysis method and seismic performance is still deficient.As to the current shortages in the seismic design for passenger railway in china,some important problems are systematically studied in present paper,including response factor at top of low pier,elastic-plastic analysis of pier, simply ductile seismic design method of pier,pier seismic fortification criterion.The principal contents are as follows:(1)Fist of all,the background and significance of the present subject are introduced. Comprehensive discuss proceed from development of domestic and overseas high railway and structure types to current problem of passenger railway in china.Main questions in the seismic design of passenger railway are put forward,and problems to be solved urgently are researched.(2)The foundation of passenger railway can't be regarded as rigidity foundation because of the pile group,so the interaction between structure and foundation for influences of earthquake reaction must be taken into account.An analytical solid model of pile-soil-pier is established for short bridge piers of ratio of shear span.A simplified analytical model of pile-soil-pier of beam unit is established for middle bridge because beam units can satisfy calculated accuracy and decrease work time by comparing solid unit model with beam unit model.Real restraint function is simulated by subgrade spring in model.Influent factors,such as soil additional mass,damp coefficient and base factor, are considered in models. (3)Judge criterion that is suitable for static seismic design of passenger railway is presented.The research subjects in this paper are low shear-span round-ended pier, which height is below four meters and spans are twenty meters,twenty-four meters,and thirty-two meters,respectively.The results by elastic-plastic time history analysis are counted and analyzed,which the influence of different base coefficient and every forty earthquake waves of four types of site as excitation have been taken into consideration. When frequency is from 4.7Hz to 9.8Hz,structural response factor at top of pier range from 1.0 to 1.2 and change very small,structure may be taken as rigidity and direct analyze as static method.A computed simplified model of rigidity pier of passenger railway is established,and the method is more accuracy by the example proof.(4)The research subjects in this paper are round-ended pier whose height is four meters to twenty meters.Main factors of base condition,earthquake wave and span for influencing elastic-plastic earthquake response characteristic are analyze,influence laws of bridge response characteristic,yield and damage from are obtained.As foundation yield prior to bridge pier,yield intensity of bridge pier is reduced by selected hollow section under meet operational requirements.When D_i/D is greater than equal 0.3 and less than equal 0.7,yield intensity of bridge pier is reduced,plastic hinge appear in pier bottom and pile group do not yield,which solved inconsistent design problem between piers and foundation.When bridge pier yield prior to foundation,the ductile design principle and construct measures are presented.(5)Simply ductile seismic model that solved the earthquake response parameters of the structure in simply way was established,and calculated results between in the simply way and in history time analysis way were compared.The model is enough calculated accuracy under 15 meters high in engineering seismic.(6)Seismic hazard level,performance objectives,seismic analysis,and design method of passenger railway bridges are given.Four main steps are:conceptual design, force/strength based design under occasional earthquake,displacement-based design under rare earthquake and detailing constructional measures design.A design example is given also.