本文選題：混凝土結(jié)構(gòu)　切入點：氯離子　出處：《廣西大學》2017年碩士論文

【摘要】：在氯化物環(huán)境中,氯離子通過擴散作用侵入混凝土內(nèi)部造成的鋼筋銹蝕和混凝土保護層開裂剝落等耐久性退化現(xiàn)象,是導致鋼筋混凝土結(jié)構(gòu)難以滿足預(yù)定設(shè)計使用年限的重要原因之一。因此,準確分析混凝土中氯離子的擴散過程,并建立相應(yīng)的解析模型,是氯化物環(huán)境下混凝土結(jié)構(gòu)耐久性分析與設(shè)計的重要前提。分析表明,氯離子擴散系數(shù)和混凝土表面氯離子濃度的時變性對氯離子的擴散過程具有重要影響。同時,混凝土結(jié)構(gòu)的幾何外形也會影響混凝土中氯離子的擴散過程和積聚規(guī)律。然而,現(xiàn)有的氯離子擴散解析模型無法綜合考慮氯離子擴散系數(shù)和混凝土表面氯離子濃度的時變性以及混凝土結(jié)構(gòu)幾何外形等因素的影響,導致難以合理描述混凝土中氯離子的擴散過程,計算精度和適用性有限。鑒于此,本文綜合考慮氯離子擴散系數(shù)和混凝土表面氯離子濃度的時變性及混凝土結(jié)構(gòu)幾何外形對氯離子擴散過程的影響,分別建立了矩形和圓形截面混凝土中氯離子雙時變擴散的解析模型,在此基礎(chǔ)上提出了混凝土結(jié)構(gòu)的耐久性定量設(shè)計方法。主要研究內(nèi)容包括:(1)綜合考慮氯離子擴散系數(shù)和混凝土表面氯離子濃度的時變性,基于三維正交直角坐標系下的Fick第二定律擴散方程,結(jié)合變量代換法和杜哈梅爾定理,建立了矩形截面混凝土中氯離子雙時變擴散的解析模型,從而克服了現(xiàn)有解析模型無法綜合考慮氯離子擴散系數(shù)和混凝土表面氯離子濃度的時變性以及氯離子擴散維數(shù)等因素影響所存在的缺陷。通過與數(shù)值分析結(jié)果和現(xiàn)場實測數(shù)據(jù)的對比分析,驗證了該解析模型的有效性和適用性。分析結(jié)果表明:氯離子擴散系數(shù)和混凝土表面氯離子濃度的時變性對混凝土中氯離子濃度的分布規(guī)律具有顯著影響;所建立的雙時變解析模型不限定混凝土表面氯離子濃度的時變函數(shù)形式,具有適用性強、計算精度高等優(yōu)點。(2)基于三維柱坐標系下的Fick第二定律擴散模型,綜合考慮氯離子擴散系數(shù)和混凝土表面氯離子濃度的時變性,結(jié)合變量代換、杜哈梅爾定理和變量分離法,建立了圓形截面混凝土中氯離子的二維和三維雙時變擴散解析模型,并通過與數(shù)值分析結(jié)果進行對比,驗證了該解析模型的有效性。分析結(jié)果表明,該解析模型不限定混凝土表面氯離子濃度的時變函數(shù)形式,計算精度較高,適用性較強,為圓形截面混凝土中氯離子的二維和三維擴散過程分析提供了有效途徑。(3)基于所建立的混凝土中氯離子雙時變擴散的解析模型,結(jié)合氯離子擴散場補償長度理論和混凝土結(jié)構(gòu)的耐久性控制區(qū)模型,確定了混凝土結(jié)構(gòu)耐久性設(shè)計參數(shù)與設(shè)計使用年限、鋼筋脫鈍的臨界氯離子濃度、混凝土表面氯離子濃度、混凝土保護層厚度等參數(shù)之間的量化關(guān)系,提出了海洋氯化物環(huán)境下混凝土結(jié)構(gòu)的耐久性定量設(shè)計方法。通過與傳統(tǒng)的耐久性設(shè)計方法對比,驗證了該方法的有效性和適用性,從而解決了傳統(tǒng)耐久性設(shè)計方法缺乏定量的耐久性設(shè)計模型,無法定量計算確定耐久性設(shè)計參數(shù)所存在的缺陷。
[Abstract]:In chloride environment, chloride ion diffusion through the invading of concrete caused by reinforcement corrosion and concrete protective layer cracking and durability degradation phenomenon, is the result of reinforced concrete structure is one of the important reasons is difficult to meet the predetermined design life. Therefore, accurate analysis of the chloride ion diffusion in concrete, and to establish the corresponding analytical model that is an important prerequisite for the design and analysis of durability of concrete structures in chloride environment. Analysis shows that the diffusion process plays an important role in degeneration of chloride ion diffusion coefficient and the concrete surface chloride ion concentration of chloride ion. At the same time, the geometry of the concrete structure will affect the diffusion process and the accumulation of chloride ions in concrete yet. Not, considering the chloride diffusion coefficient and the surface chloride ion concentration of concrete chloride ion diffusion model of the existing time Effect of modified concrete structure and geometry and other factors, make it difficult to describe the diffusion process of chloride ion in concrete, the calculation accuracy and applicability is limited. In view of this, considering the effect of chloride ion diffusion coefficient and the concrete surface chloride ion concentration and time dependence of geometric shape on concrete chloride ion diffusion process, analysis model of concrete rectangular and circular cross section of chlorine ion in dual time-varying diffusion are established, based on the proposed quantitative durability design method of concrete structure. The main research contents include: (1) considering the chloride ion diffusion coefficient and the concrete surface chloride concentration change with time and the Fick's second law of 3D orthogonal cartesian coordinates. The diffusion equation based on the combination of variable substitution and the Duhamel theorem, the rectangular section of chloride ions in concrete double variable diffusion solution to establish In order to overcome the existing analysis model, analytical model not considering the defects of degeneration and chloride ion diffusion dimension of chloride ion diffusion coefficient and the surface chloride concentration of concrete. By analyzing and comparing the results with measured data and numerical analysis, verify the validity and applicability of the model analysis. The results showed that there are significant effect on the distribution of time variation and chloride diffusion coefficient of concrete surface chloride ion concentration of chloride ion concentration in concrete; the double variable analytical model is not limited to the concrete surface chloride concentration of the time-varying function form, has strong applicability and accuracy. (2) diffusion model based on Fick's second dimensional cylindrical coordinates, considering the chloride ion diffusion coefficient and the concrete surface chloride concentration change with time and with variable substitution, Duhamel theorem and variable separation method, a two-dimensional chloride ion in concrete circular section and three-dimensional double time-varying diffusion analytical model is established, and the results were compared with numerical analysis, to verify the validity of the analytical model. The analysis results show that the analytical model does not limit the concrete surface chloride ion concentration variation function, high accuracy, strong applicability, provides an effective way for the two dimensional analysis of chloride ion in concrete circular section and three-dimensional diffusion process. (3) developed analytical model of chloride ions in concrete double diffusion based on the combination of chloride ion diffusion field length compensation theory and the durability of concrete structure control model sure, the concrete structure durability design parameters and design life, critical chloride concentration of rebar depassivation, surface chloride ion concentration of concrete, thickness of concrete protective layer The quantitative relationship between the parameters of the proposed marine chloride environment the durability of concrete structure in quantitative design method. By comparing with the traditional method of durability design, verify the validity and applicability of the method, so as to solve the traditional method for durability design lack of durability design model of quantitative and quantitative calculation to determine the defects the durability design parameters exist.

【學位授予單位】：廣西大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU528

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