基于海洋环境的预应力混凝土箱梁耐久性设计与长寿命措施分析

发布时间：2018-06-02 08:46

  本文选题：海洋环境 + 高性能混凝土　； 参考：《南京航空航天大学》2014年硕士论文

【摘要】：海洋环境中因氯离子扩散造成混凝土结构的破坏己经成为全球土木工程界普遍关注的耐久性灾害。对于后张法预应力混凝土箱梁(简称预应力混凝土箱梁),由于长期受到海洋盐雾等侵蚀作用,大量氯离子侵入混凝土中,致使箱梁中的钢筋严重锈蚀,从而混凝土箱梁难以达到100年的设计寿命要求。本文分别对混凝土箱梁悬臂板、斜腹板以及底板钢筋达到5%和10%起锈概率时的服役寿命进行了预测,并提出了能够延缓钢筋起锈时间的一系列措施,从而提高箱梁耐久性、保证结构能满足100年的服役要求。本文主要得出以下结论:(1)为了研究不同掺量矿物掺合料混凝土的耐久性能,试验采用4组不同配合比的高性能混凝土。矿物掺合料等量替代水泥,F0、F20分别表示粉煤灰掺量为0和20%的C60普通混凝土和C60高性能混凝土,S30表示表示矿渣掺量为30%的C80高性能混凝土,S60分别表示矿渣掺量为60%的C50高性能混凝土;(2)海洋大气环境下,预应力混凝土箱梁的耐久性主要取决于悬臂板与斜腹板以及箱梁底板钢筋的起锈时间。预应力筋在长达100年的服役过程中,因波纹管的保护作用与其保护层厚度较大,不可能发生因氯离子扩散渗透导致的钢筋锈蚀作用;(3)海洋大气环境下预应力混凝土箱梁,若不采取防腐措施,则悬臂板与斜腹板在5年之内就会发生锈蚀,箱梁底板主筋的锈蚀时间相对较长。对于F0、F20、S30及S60高性能混凝土,防锈效果依次增强,其中F0与F20效果差别不明显,S30与S60底板的服役寿命均可达到50年;(4)海洋大气环境下预应力混凝土箱梁,若在悬臂板与斜腹板涂刷浸渍深度不小于8mm的硅烷,并在箱梁底板涂刷浸渍深度约0.5~2mm的硅烷,则箱梁可以达到100年、甚至120年的设计寿命要求,其中,采用S60高性能混凝土效果最好;(5)为满足海洋大气环境下长寿命预应力混凝土箱梁的耐久性要求,需选用高性能混凝土,并施加一定的附加防护措施,如:适当增加保护层厚度,选用不锈钢钢筋,在箱梁表面涂刷硅烷,在配制混凝土过程中掺入阻锈剂等;(6)若预应力混凝土箱梁底板的第一排主筋采用不锈钢钢筋,混凝土材料选用F20、S30或S60高性能混凝土并掺加一定量的阻锈剂,在悬臂板与腹板表面涂刷渗透深度不小于8mm的硅烷,则海洋大气环境下预应力混凝土箱梁的寿命有可能达到500年。
[Abstract]:The damage of concrete structures caused by chloride ion diffusion in marine environment has become a global civil engineering field of universal concern for durability disasters. For the post Zhang Fa prestressed concrete box girder, due to long term erosion of sea salt mist, a large amount of chloride ions intrude into concrete, resulting in serious corrosion of steel bars in box girder. Therefore, the concrete box girder is difficult to meet the design life requirement of 100 years. In this paper, the service life of cantilever slab, inclined web plate and bottom steel bar of concrete box girder is predicted when the probability of rusting is 5% and 10% respectively, and a series of measures are put forward to delay the rusting time of steel bar, so as to improve the durability of box girder. Ensure that the structure meets 100 years of service requirements. In order to study the durability of concrete with different contents of mineral admixtures, four groups of high performance concrete with different mix ratio are used in the experiment. Mineral admixture is used to replace cement F0 / F20 for ordinary concrete with fly ash content of 0 and 20% and C60 high performance concrete for C60 high performance concrete with 30% slag respectively. S60 indicates slag content is 60%, respectively. In the marine atmosphere, The durability of prestressed concrete box girder mainly depends on the rusting time of cantilever slab, inclined web plate and steel bar on box girder floor. In the course of 100 years of service of prestressed tendons, because the protective effect of bellows and the thickness of protective layer are great, it is impossible to take place in the prestressed concrete box girder caused by chloride ion diffusion permeation. If the anticorrosive measures are not taken, the corrosion of the cantilever plate and the inclined web will occur within 5 years, and the corrosion time of the main reinforcement on the bottom plate of the box girder is relatively long. For F0 / F20 / S30 and S60 high performance concrete, the antirust effect is enhanced in turn, and the service life of S30 and S60 bottom slabs can reach 50 years or 4) under marine atmosphere, and the difference between F0 and F20 is not obvious. If silane with a depth of not less than 8mm is applied on the cantilever and inclined web, and silane with a depth of about 0.5~2mm on the bottom of the box girder, the box girder can meet the design life requirement of 100 years or even 120 years. In order to meet the durability requirements of long-life prestressed concrete box girder in marine atmosphere, high performance concrete should be selected and some additional protective measures should be applied, such as increasing the thickness of protective layer appropriately. Stainless steel bars are selected, silane is applied on the surface of box girders, rust inhibitor is added in the process of making concrete, etc.) if the first row of main bars of prestressed concrete box girders is made of stainless steel bars, If F20 S30 or S60 high performance concrete is used as concrete material and a certain amount of rust inhibitor is added, silane whose penetration depth is not less than 8mm on the surface of cantilever slab and web plate, the life of prestressed concrete box girder can reach 500 years in marine atmosphere.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U448.35
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本文编号：1968150