Research Of Temperature Stress And Anti-cracking Measures For Railway Bridge Pier In Arid Regions

With the development of economy in northwest of China,the demand for high-speed railway has been improving constantly.The number of railway bridges for high-speed has been growing dramatically,meanwhile the most of bridge piers and foundations for high-speed railway bridges are all belong to mass concrete.Since the beginning of mass concrete,its temperature field and temperature stress is not always easy to control,mass concrete structure produces many cracks easily.It belongs to the kind of environmental conditions that temperature varies widely from day and night in the region of Xining.In this environment condition,the bridge builders constructe the massive piers.The distribution of temperature field and stress field of bridge pier are more complex,and more difficult to control,bridge piers are easier to produce large number of temperature cracks,those cracks have great influence on the normal use and durability of bridge,even imperil the safety of the bridge.for the high-speed railway bridges have higher requirements for bearing capacity of bridge piers nowadays.It is particularly urgent to summarizethe distribution regularity of temperature field and stress field in the arid region of northwest China.In this paper,we determine to a railway grand bridge of arid areas as the engineering background,study the change rule of temperature field and stress field of piers that is created by pouring concrete in different seasons,combinate with the special environment of arid areas,it is concluded that laws and measures of crack prevention about massive piers of arid areas,those laws and measures can prevent and control temperature cracks that produce during construction and operation.The main points of this article is/are as follows:(1)Through summarizes the regularity of temperature field of piers named as 31#,17#,13# and 28#pier that is created by pouring concrete in different seasons,it is obtained that change rules of temperature field about mass concrete of arid areas.Though change rules of temperature field about mass concrete,the builders guide the engineering construction.A finite element model for the massive piers is established,calculated data of piers that is created by pouring concrete in different seasons is obtained.Though calculated data compares with the measured values,it is concluded that the key issues of ansys modeling,such as m value on cement hydration.(2)The center temperature and surface temperature data of the pier that is created is obtained by pouring concrete in different seasons by the construction calculation formula.Though temperature calculating data compare with the measured temperature data,the applicability of the construction thermal calculation formula is verified in arid region of northwest;If it is not applicable,the formula is corrected by change some controllable parameters.(3)Technology that prevents cracks generation of massive pier are researched.Some condition may cause cracks generation in concrete,such as improper conservation measures what pier shaft has before and after dismantle mold,appropriateness of time dismantle mold and severe ambient air temperature.Fairly good conservation measures is useful to prevent greatly cracks generation,because equivalent heat release coefficient of piers shaft that constructe the massive piers in winter is smaller.As ambient air temperature is well,the bridge buliders may have high probability to ignore the conservation measures for piers shaft that constructe in spring and summer,but this condition can influence stress of concrete,however cracks generation in concrete is due to excessive stresses caused by improper conservation measures.Aiming at the possible problem,the phenomenon was alerted by the practical engineering case,then further research to the problem that concrete is maintained by improper maintenance,finally obtain good methods and measures to prevent cracks generation in concrete.