Study On Hydration Effect And Temperature Control Measures Of Anchorage Construction Of Suspension Bridge

As an important bearing structure of suspension bridge,anchorage of suspension bridge is a typical mass concrete structure.The safety and durability of anchorage are very important.In the construction process of suspension bridge anchorage,the hydration heat release of cementitious materials in concrete and improper temperature control are easy to cause cracks in the anchorage concrete.Based on the construction monitoring project of Chongqing Youxi Yangtze River Bridge,taking the gravity anchor and tunnel anchor plug concrete engineering in the substructure as the research object,this paper studies the hydration effect of the anchor in the construction stage through theoretical analysis,engineering practice and finite element simulation,and explores the relevant engineering countermeasures(1)Based on the analysis of the difference of hydration environment between gravity anchor and tunnel anchor plug,combined with their engineering characteristics,the corresponding temperature control measures are formulated.The temperature field of gravity anchor and tunnel anchor plug in the construction stage of Youxi Yangtze River Bridge is predicted by using the general finite element software MIDAS FEA,and compared with the measured value.The results show that: the construction period field and temperature field of gravity anchor are greatly affected by the environment,the sudden drop of temperature,cold wave and other factors will increase the risk of concrete cracking;due to the surrounding rock and the closed environment in the tunnel,it is not easy to dissipate heat in the construction of the anchor plug,so the cooling method of the cooling water pipe is very important in the temperature control of the anchor plug.(2)Aiming at the influence factors of hydration in Anchorage construction stage,such as molding temperature and environmental temperature,and analyzing the physical principle behind the block layered construction method of anchorage,the numerical analysis of concrete layered thickness and thermal insulation material is carried out,and the influence law of each factor on concrete temperature field is studied.Aiming at the current situation that the empirical method is often used in the design of pipe cooling system,the layout form of cooling water pipe,the design method of thermal insulation material are analyzed On this basis,a design method of pipe cooling system based on critical Reynolds number is proposed.The results show that: the control of molding temperature can effectively reduce the peak temperature of concrete;the use of materials with good thermal insulation effect and higher ambient temperature are conducive to reducing the temperature difference between inner and outer surface;the design method of pipe cooling system based on critical Reynolds number can provide a new idea for the design of cooling water pipe,which has a certain engineering significance to improve the economy and rationality of pipe cooling system.(3)Based on the thermal insulation performance of the surrounding rock of the anchor plug body,a new method to control the cracks of the anchor plug body under the condition of negative temperature difference is proposed,and the feasibility of this method is demonstrated by numerical experiments.This paper summarizes the temperature control measures suitable for the whole construction period of suspension bridge anchorage mass concrete structure;in order to overcome the difficulty of garbage cleaning in the post pouring belt and the difficulty of construction,in view of the current situation that the anchorage mainly adopts the block layered construction,it shows that the "skip bin method" based on the theory of "resistance and release" is also suitable for the construction of gravity anchorage.