海工环境PHC管桩设计寿命计算

Calculations of Designed Lifetime of PHC Pipe Piles in Marine Environment

氯离子引起的钢筋锈蚀是影响钢筋混凝土结构耐久性的主要原因之一。基于Fick第二定律,推导了PHC(Prestress high concrete)管桩氯离子扩散的解析解,并对PHC管桩设计寿命进行了预测,且考虑了离心分层和温度作用对PHC管桩设计寿命的影响。结果表明:离心分层和温度对PHC管桩中氯离子扩散影响较大,而初始氯离子含量对其影响较小。综合考虑离心分层和温度影响,确定了海工环境中PHC管桩的设计要求,即对于要求服役寿命大于50a的工程,壁厚应大于100mm,且砂浆层不宜大于10mm,而对于服役寿命要求大于100a的工程,应选用壁厚150mm的PHC管桩,且砂浆层宜小于30mm。

Chloride-induced reinforcement corrosion is one of the main factors affecting the durability of concrete.This paper obtained the analytical solution of chloride ions diffusion of prestress high concrete(PHC) pipe piles in cylindrical coordinates under different diffusion coefficient conditions based on the Fick second law.In normal environment(i.e.,temperature difference between 0-15℃),the difference between inside and outside diffusion coefficients is generally 2times.Considering the special process of PHC pipe piles,we used the electric flux to calculate the diffusion coefficients.The calculated results show that centrifugal stratified and temperature both have a major influence on the chloride ions diffusion,and initial chloride content has less influence.The calculated results are effective with respect to the reinforced block effect.The half a wall thickness was used as a diffusion depth to calculate the design life of PHC pipe piles.It is suggested that the wall chickness should be greater than 100mm and the mortar layer should not be greater than 10mm if the service life of PHC pipe piles is>50years in marine envrionment.The wall chickness of 150mm should be used and the mortar layer should be less than 30mm if the service life is >100years.