西部盐渍土地区混凝土桥墩柱抗震性能腐蚀劣化机理的研究

western saline soil area includes Inner Mongolia, Ningxia, Qinghai, Xinjiang, Gansu, and so on. Many types of corrosive ions exist in the western saline soil area, their concentrations are higher, and their corrosive deterioration for service performance of reinforced concrete structure is stronger. At the same time, frequent earthquake seriously threatens reinforced concrete structure in the western saline soil area. A large number of bridge construction is started during the implementation of the western great exploitation strategy, and bridge structures are faced with corrosive action of saline soil environment. Especially the bridge pier is corroded strongly because it is directly contacted with saline soil.So reinforced concrete bridge pier is selected as research object in this project. The experimental solution will be prepared according to the chemical constituents of saline soil and bridge pier will be corroded in the dry/wet cycle method. The research contents include corrosive deterioration of steel bar and concrete cover, seismic performance of bridge pier in the various cycle stage, earthquake damage analysis of bridge pier and time-dependent seismic reliability of bridge pier in this research program. Seismic damage theory and reliability theory are applied. Influence of corrosive environment on seismic performance of bridge pier is evaluated. The available results will provide research background and theoretical basis for the construction and earthquake disaster prevention of bridge structures.

西部盐渍土地区包括内蒙古、宁夏、青海、新疆、甘肃等地区，主要特点是土壤中含有多种类高浓度腐蚀性离子，对混凝土结构使用性能具有很强的腐蚀劣化作用。同时，西部大部分地区属于地震频发地区，地震对混凝土结构具有毁灭性的破坏作用。随着西部大开发战略的实施，西部地区桥梁工程大量兴建，混凝土桥梁结构抗震性能面临着盐渍土环境的腐蚀劣化作用，尤其是与盐渍土壤接触的混凝土桥墩柱，受到的腐蚀作用最显著。因此，本项目拟以混凝土桥墩柱为研究对象，根据西部盐渍土壤中的化学成分，配制试验溶液，采用干湿循环腐蚀方式，研究不同干湿循环阶段混凝土桥墩柱的抗震性能，分析混凝土保护层和钢筋的腐蚀劣化规律；同时，采用结构地震损伤理论和可靠度理论，进行西部盐渍土地区混凝土桥墩柱地震损伤分析和抗震性能时变可靠度分析，评价西部地区盐渍土环境对混凝土桥墩柱抗震性能的影响。为西部盐渍土地区桥梁工程建设和抗震防灾提供必要的研究背景和理论基础。

本项目以西部盐渍土地区桥墩柱腐蚀劣化为背景，制作了13个混凝土桥墩柱试件，以及相应的混凝土立方体试件。根据西部盐渍土壤中的化学成分，配制试验溶液，采用干湿循环腐蚀方式对试件进行了腐蚀试验，研究了不同干湿循环阶段混凝土桥墩柱的抗震性能，分析了混凝土保护层和钢筋的腐蚀劣化规律；同时，采用结构地震损伤理论和可靠度理论，进行了西部盐渍土地区混凝土桥墩柱地震损伤分析和抗震性能时变可靠度分析，评价西部地区盐渍土环境对混凝土桥墩柱抗震性能的影响；建立了混凝土桥墩柱屈服位移时变性模型。结果表明，低周反复荷载作用下桥墩柱根部塑性铰区弯曲破坏。随着钢筋名义锈蚀率的增大，试件屈服位移，滞回耗能、刚度逐渐减小，试件的抗震性能逐渐降低。相同钢筋名义锈蚀率下，小轴压比试件抗震性能优于大轴压比试件。氯离子浓度沿混凝土保护层厚度逐渐降低，随干湿循环时间增加逐渐增大。混凝土立方体抗压强度、劈裂强度随干湿循环周期增加，呈先增加后降低趋势。以Park-Ang损伤模型为基础建立了地震损伤模型，和桥墩柱地震损伤安全评价的标准。同时考虑混凝土损伤和钢筋损伤及材料强度劣化，建立了抗剪承载力时变桁架-拱模型，其计算值与实验值较为符合。考虑氯盐环境对桥墩柱的影响，建立了桥墩柱屈服位移的时变性模型，计算值与试验值之比介于0.96～1.06范围内，吻合较好。本项目相关研究成果可为西部盐渍土地区桥梁工程建设和抗震防灾提供必要的研究背景和理论基础。