Research Of Temperature Crack Control Technology For Railway Bridge Concrete Pier Constructed In Winter Of Plateau Region

With the rapid growth of our nation’s economy and technology,our nation’s railwayconstruction is in the historical period of rapid development.With the development ofhigh-speed railway,bridge engineering in railway construction has an increasingly prominentposition,mass concrete structure has been increasing gradually in bridge construction projects.Combine effect between hydration heat inside the concrete and surrounding temperature is animportant cause of mass concrete cracking.At the same time,the special climatic of thenorthwest plateau made the temperature crack problem of mass concrete moreprominent.Therefore,there has an urgent need to study and explore appropriate solutions toimprove the quality of construction to ensure the safety and durability of the structure.This paper is based on a railway bridge pier which constructed in winter of Xining,analyze the temperature field and temperature stress of this mass concrete structure, and studythe correspondingly thermal crack control measures.The main work of this paper can besummarized as the following four areas:(1)Elaborate the calculation principles of temperature field in mass concrete,includingheat transfer equations, boundary conditions, hydration heat of cement and other formulas;andintroduce the correspondingly finite element method,provide a theoretical basis for simulationanalysis of mass concrete bridge pier.(2)Based on heat transfer theory and finite element method,study the distribution andvariation of temperature field and thermal stress in concrete pier by simulation thetemperature field and thermal stress in a railway bridge pier which constructed in winter ofnorthwest plateau.Meanwhile, analyze the temperature control situation of this concrete pierby simulation and empirical formulae.(3)According to the actual temperature of this concrete pier collected at constructionsite,draw temperature-time curves of the concrete pier constructed in winter of northwestplateau.Obtain reasonable hydration heat parameters by comparing theoretical results withactual temperature measurement results,provide a reference for simulation temperature fieldof similar mass concrete pier.Meanwhile,proving the feasibility of simulation analysis formass concrete temperature field and temperature stress by MIDAS/FEA software.(4)Studying temperature field and temperature stress effected by different conservationmeasures,including concrete casting temperature,the temperature inside insulation shed andthe equivalent heat transfer coefficient of heat preservation material after removal of thetemplate etc..And discussing the comprehensive crack control measures of mass concretefrom three fileds,including structural design,concrete materials selection and construction methods.Obtain reasonable and effective conservation measures for railway bridge piersconstructed in winter of northwest plateau.