【作者】 徐立；

【导师】 程旭东； 王春；

【作者基本信息】 中国石油大学(华东) ， 建筑与土木工程（专业学位）， 2017， 硕士

【摘要】 钢筋混凝土结构的耐久性研究是国内外研究的重点和难点课题,氯离子侵蚀一般是海洋环境中造成钢筋混凝土结构耐久性破坏的前提条件。对于实际混凝土工程的腐蚀,往往是荷载和环境综合作用的结果。因此受力钢筋混凝土构件氯离子诱导的锈胀开裂研究,对于混凝土结构的耐久性设计和优化具有重大意义。本文采用理论分析与数值模拟相结合的方法,以海洋环境下钢筋混凝土构件为研究对象,基于COMSOL和ABAQUS有限元软件,分别对有应力和无应力下混凝土构件的腐蚀特性进行了研究,同时结合阴极保护对电化学机制进行了分析和对比。具体内容是:1、建立无荷载作用下钢筋混凝土梁数值模型,基于腐蚀电化学相关机制,分别研究了钢筋所处位置和保护层厚度对腐蚀特性的影响,并对异类钢筋之间的电化学反应进行对比,同时探讨了不同钢筋间距下的混凝土开裂模式。2、建立荷载环境耦合作用下钢筋混凝土梁数值模型,考虑荷载损伤作用对温度传递、水分运输和氯离子传输模型的修正,研究了影响梁纯弯段损伤系数的相关因素,对氯离子扩散行为、去钝化行为分别进行了分析,并对不同损伤等级下的腐蚀电流变化、锈蚀产物累积和锈胀裂缝的产生过程进行了研究。3、建立混凝土横向和纵向截面的阴极保护数值模型,基于电化学保护机制,研究了宏电池腐蚀情况下电流密度和电势的分布,通过与相关设计标准的比较来对结构和理论模型进行优化,从而起到预防和控制混凝土开裂的作用。结果表明:无荷载情况下,角部钢筋侵蚀效率显著高于中部钢筋;保护层厚度的变化极大影响腐蚀电流的累积;带肋钢筋优先发生电化学腐蚀且腐蚀速率更大,肋间距和最大肋宽度都会影响腐蚀电流;钢筋间距为2.3倍钢筋直径时开裂程度和损失最小。有荷载情况下,损伤修正系数与荷载强度和混凝土强度都有关;裂缝宽度与最大锈胀位移的关系为w=0.3937-0.3796cos(9.292S_max)-0.07293sin(9.292S_max);高等级损伤产生的裂缝影响区不可忽略。在电化学保护中,保护电流更趋向流入阴极区,当外加电流能抑制宏电池腐蚀时保护电流才会流入阳极区;宏电池腐蚀显著提高阴极保护的非均匀性,保护电流能够有效地抑制电化学不相容性导致的宏电池腐蚀。更多还原

【Abstract】 The durability study of reinforced concrete structure is an important and difficult task,and chloride ion penetration usually is the precondition of durability damage about reinforced concrete structure in marine environment.As for the corrosion of real concrete engineering,it is the result of load and environment effect.Thus the cracking study due to chloride-induced corrosion expansion for stressed reinforced concrete members is meant for durability design and optimization of concrete structures.This thesis used the method of combining theoretical analysis and numerical modeling and took marine reinforced concrete members as the research object.At the same time,the corrosion character of stressed concrete component and unstressed concrete component was studied,and combining cathodic protection the electrochemical mechanism was analyzed and compared based on COMSOL and ABAQUS finite element software.Details are as follows:1.Establishing the unstressed reinforced concrete beam numerical model based on related electrochemical corrosion mechanism,studying the effect of reinforcement position and cover thickness on concrete corrosion character and contrasting the electrochemical reaction between different kinds of steel.Also,the cracking figures under different rebar spacing were discussed.2.Establishing the reinforced concrete beam numerical model under the coupling of load and environment,considering the correction of load damage for temperature transit,water transport and chloride ion transport model and studying the related factors affecting damage coefficient of beam pure bending section.At the same time,the chloride ion diffusion and depassivation behavior were analyzed.Also,the corrosion current changing,corrosion product accumulation and corrosive crack generation process under different damage levels were studied.3.Establishing the numerical model of cathodic protection for concrete cross section and longitudinal section and studying current and potential distribution under macrocell corrosion.Thus we could optimize the structure and theoretical model by comparing the modeling result with the related design standard.Finally,it can work on preventing and controlling concrete cracking.The result showed that:In the case of no loading,the erosion efficiency of corner steel is evidently higher than that of middle steel;The change of cover thickness heavily influences the accumulation of corrosion current;The electrochemical corrosion of ribbed bar is faster and its corrosion rate is bigger than those of plain round bar,and rib spacing and max rib width can affect the corrosion current;Cracking degree and damage is minimum when steel spacing is 2.3 times the steel diameter.In the case of loading,damage correction coefficient is related to load intensity and concrete strength;The relation between crack width and max corrosive displacement is described as w=0.3937-0.3796cos(9.292S_max)-0.07293sin(9.292S_max);The crack influenced area caused by high level damage can’t be neglected.In the electrochemical protection,the protective current tends to flow into cathode space and if the impressed current can suppress macrocell corrosion the protective current can flow into anode space;Macrocell corrosion evidently improves the heterogeneity of cathodic protection and protective current can effectively control the macrocell corrosion for electrochemical incompatibility.更多还原