摘要
基于改进的碳化深度预测模型,利用最新的CO2浓度数据,发展了时变可靠度模型计算混凝土结构在碳化腐蚀下的开裂概率。建立概率模型可以考虑CO2浓度、扩散过程、劣化机理、钢筋的位置、保护层深度、腐蚀电流的随机性和不确定性。计算了不同耐久性设计状态下和不同的锈胀开裂宽度准则下在碳化腐蚀作用下的开裂风险。建立了全寿命成本概率模型,比较了在碳化腐蚀下的不同耐久性措施和不同锈胀开裂宽度准则的全寿命经济性能,提出了在碳化腐蚀作用下未来混凝土结构保护层设计厚度。研究发现对于保护层厚度为40 mm和水灰比为0.45的混凝土结构,腐蚀开裂概率仅为0.003,碳化腐蚀损伤可以忽略。然而,对于保护层厚度为20 mm和水灰比为0.55的混凝土结构,结构服役50 a后,有0.18的概率开裂。在100 a后,概率提高到0.37,其全寿命成本为中等耐久性混凝土结构的3.1倍。当现有结构保护层厚度为小于或等于55 mm时在未来排放策略下保护层厚度需要提高3~15 mm以疏缓RC桥梁的碳化腐蚀损伤。
Based on the improved carbonation depth prediction model,by using the latest time-dependent CO2 concentration data,a time-dependent structural reliability model for computing the cracking probability of concrete structure subject to carbonation-induced corrosion was developed,considering CO2 concentration and emission,deterioration mechanism,position of steel reinforcement,concrete cover thickness,and randomness and uncertainty of corrosive current.The cracking risks under various durability design specifications and different corrosion-induced crack widths criterions subject to carbonation-induced corrosion were calculated,and the related economic performance was compared by the developed life-cycle cost probabilistic model.An increase in future design cover thickness for concrete carbonation-induced corrosion was presented.It is found that（1） for cover thickness=40 mm and water-cement ratio=0.45,the probability of cracking of concrete structure is 0.003,and the effect of carbonation-induced corrosion can be neglected;（2） for cover thickness=20 mm and water-cement ratio=0.55,the probability of cracking is 0.18 after 50 years,and the probability of cracking increases to 0.37 over the next 100 years,its life-cycle cost is 3.1 times than that of medium durability concrete structure;（3） if the existing design cover thickness is lower than or equal to 55mm,an increase in design cover thickness of 3~15mm is needed to mitigate corrosion damage due to concrete carbonation under future emission scenarios.
出处
《公路交通科技》
CAS
CSCD
北大核心
2011年第2期37-44,51,共9页
Journal of Highway and Transportation Research and Development
基金
国家自然科学基金资助项目(5087804351008037)
湖南省科技计划应用基础项目(2010FJ3172)
长沙理工大学桥隧重点学科创新基金资助项目(2010qs-04)
关键词
桥梁工程
RC桥梁
碳化腐蚀
耐久性
开裂风险
时变可靠度
全寿命成本
bridge engineering
RC bridge
carbonation-induced corrosion
durability
cracking risk
time-dependent reliability
life-cycle cost
