盐腐蚀钢筋混凝土构件力学性能

沿海或近海地区的混凝土结构、需撒除冰盐的公路或城市道路桥梁以及恶劣环境(如高盐碱土壤等)条件下的混凝土结构容易遭受氯离子的侵蚀,导致结构较早损坏,对结构的耐久性、安全性及可靠性带来极大危害。这一问题已引起人们的广泛关注,成为研究的一大热点。本文在国内外已有研究成果的基础上,结合国家自然科学基金(59878031)项目,通过一系列受腐蚀构件的试验,采用试验及非线性有限元法,研究了受腐蚀构件的开裂、变形、破坏机理,主要作了以下几方面的工作。首先,研究了氯离子在混凝土中的扩散机理和侵蚀机理,以及氯离子对钢筋的去钝化和腐蚀机理。探讨了混凝土中氯离子扩散系数和钢筋锈蚀的影响因素,建立了混凝土内部氯离子结晶膨胀的应力计算模型和用于评估钢筋锈蚀程度的计算公式。总结了在混凝土中进行氯离子浓度、氯离子扩散性、钢筋锈蚀等的各种检测手段和测定方法。其次,详细讨论和总结了混凝土在复杂受力状况下的应力-应变本构关系,论述了钢筋与混凝土间的粘结破坏机理,提出了研究遭受盐腐蚀的钢筋混凝土构件的非线性分析方法,为钢筋混凝土构件的非线性有限元分析提供了力学基础。再次,通过对钢筋混凝土构件的促进腐蚀试验,研究了受腐蚀钢筋混凝土梁正、斜截面以及轴心受压短柱力学性能的变化,采用非线性有限元分析法对试验结果分析论证,在此基础上运用极限平衡理论建立了腐蚀钢筋混凝土受弯构件正、斜截面和轴心受压短柱的计算模型。最后,研究了氯离子在混凝土中的分布规律,根据试验测定的混凝土中的氯离子含量,推导了试验构件相当时间的计算公式。该公式的推导为在实验室研究在役构件遭受腐蚀后其力学性能的变化情况奠定了坚实的基础。
逆变焊机
The marine structures, bridges required salt to thaw ice and the others exposed in adversecircumstances (such as salt-marsh, alkaline soil), are easy to be subjected to corrode by CL-.This leads the structures to be damaged early, and brings bigger harms for their safety,durability and reliability. The problem has been given rise to extensive attention and become afocus of research. Based on domestic and foreign result previously, combined with the projectof National Natural Science Foundation of China (No.59878031), through a series ofexperiments, this paper did some research on crack, warp and broken mechanism of corrodedmembers with the methods of test and nonlinear finite element analysis. The work havingbeen done in this paper is forward:1.This paper has been studied the CL-how to spread inside concrete, damage the protectivemembrane of steel rod, and corrode the both concrete and steel rod. Then analyzed theinfluences over spread factor of CL-and corrosion of steel rod. Established the stresscalculable model of crystallizing and expanding of CL-inside concrete, and the calculableformula being used for assessing the corrosive extent of steel rod. Sum up various examiningand measuring methods of concentration, spread of CL-and corrosion of steel rod.2.On the base of detailed discussion about relationship between stress and strain of concreteunder the complicated stress and the mechanism of cohesion broken between steel rod andconcrete, a nonlinear analytical method to study the corrosive reinforced concrete memberswas brought forward. This laid a mechanical foundation for nonlinear finite element analysisof the reinforced concrete members for next chapters.3.By way of the accelerated experiment of reinforced concrete members corroded by salt, thechanges of mechanical property for the obverse, oblique section of reinforced concrete beamsand short column pressed at axis were investigated. The experimental result was analyzed byusing nonlinear finite element, and then applying the theory of limited equilibrium, calculablemodels of corroded beam and column were put forward.4.The distribution law of CL-inside concrete was studied. Based on the measured density ofCL-inside concrete, a calculable formula of “corresponding time” for the experimentalmembers was worked out. This formula laid a solid foundation for the work in laboratory tostudy on the changes of mechanical property of existing corrosive reinforced concretemembers.