本文選題：混凝土 + 箱梁�。� 參考：《蘭州交通大學(xué)》2017年碩士論文

【摘要】：混凝土耐久性問(wèn)題,因?yàn)榕c混凝土結(jié)構(gòu)的長(zhǎng)期使用和安全有著密切關(guān)系而越來(lái)越受到各界關(guān)注。碳化又是影響混凝土耐久性很重要的一個(gè)方面,最顯著的影響是改變了混凝土內(nèi)部的酸堿性,引發(fā)鋼筋銹蝕、膨脹,嚴(yán)重的還會(huì)導(dǎo)致混凝土保護(hù)層開(kāi)裂甚至剝落,給結(jié)構(gòu)物的使用和安全帶來(lái)重大隱患。(1)對(duì)碳化機(jī)理進(jìn)行了闡述,推導(dǎo)擴(kuò)散控制方程,并對(duì)比了有限元軟件中熱傳導(dǎo)問(wèn)題與碳化問(wèn)題的相似性�，F(xiàn)有的相關(guān)研究都是采取一定方法,對(duì)碳化過(guò)程進(jìn)行了簡(jiǎn)化和近似,得到各種理論模型。也有很多研究是針對(duì)影響碳化的各種因素,研究其影響程度,特別是利用計(jì)算機(jī)技術(shù)研究碳化問(wèn)題時(shí),直接將多種影響因素耦合成一個(gè)主要系數(shù),這種方法更為直觀,也有顯著的效果和成果。本文基于現(xiàn)有的這些混凝土碳化模型和相關(guān)研究結(jié)論,從混凝土碳化問(wèn)題相關(guān)的各種理論出發(fā),著重考慮了混凝土箱梁在構(gòu)造特別是力學(xué)方面的特性進(jìn)行綜合分析。(2)對(duì)混凝土箱梁模型進(jìn)行快速碳化試驗(yàn),探究箱梁的特殊構(gòu)造對(duì)碳化產(chǎn)生的影響。借助有限元軟件,編寫(xiě)APDL程序,對(duì)該箱梁模型進(jìn)行數(shù)值模擬。同時(shí),結(jié)合碳化試驗(yàn)與數(shù)值模擬的結(jié)果,對(duì)數(shù)值模型進(jìn)行校準(zhǔn),同時(shí)也驗(yàn)證了利用這種方式研究混凝土碳化問(wèn)題是可靠、有效的。統(tǒng)計(jì)結(jié)果表明,受二維碳化作用的外角部區(qū)域混凝土的碳化深度最大,是非角部混凝土的1.56倍,約為內(nèi)角部混凝土的2倍。翼緣端頭區(qū)域的碳化,在早期時(shí)為簡(jiǎn)單的一維碳化作用,隨著反應(yīng)進(jìn)行到后期,由于頂板上下邊緣的碳化深度的增加達(dá)到混凝土內(nèi)部,該處碳化反應(yīng)也明顯加快。(3)對(duì)處于自然環(huán)境的混凝土箱梁,在應(yīng)力條件下的碳化性能進(jìn)行了數(shù)值分析。自然環(huán)境中由于CO2濃度很低,混凝土碳化反應(yīng)需要很長(zhǎng)的時(shí)間,對(duì)于需要在相對(duì)較短時(shí)間內(nèi)得出研究結(jié)論而指導(dǎo)實(shí)際的這個(gè)前提而言,長(zhǎng)期暴露試驗(yàn)就有了很大的局限性,因此用數(shù)值分析的方法研究碳化問(wèn)題的優(yōu)勢(shì)顯而易見(jiàn)。通過(guò)分析,得到箱梁截面上碳化深度的分布規(guī)律,并對(duì)達(dá)到混凝土箱梁保護(hù)層厚度所需的時(shí)間進(jìn)行了預(yù)測(cè)。結(jié)果表明,應(yīng)力狀態(tài)下與非應(yīng)力狀態(tài)下的混凝土箱梁,受二維碳化作用的外角部是受碳化影響最大的區(qū)域,該處碳化反應(yīng)速率高于其他部位。
[Abstract]:The durability of concrete has attracted more and more attention because of its close relationship with the long-term use and safety of concrete structures. Carbonation is also an important aspect that affects the durability of concrete. The most significant effect is to change the acidity and alkalinity of concrete, causing corrosion and expansion of steel bars, and even cracking and even spalling of concrete cover. The carbonation mechanism is expounded, the diffusion control equation is derived, and the similarity between heat conduction problem and carbonation problem in finite element software is compared. The existing research methods have been used to simplify and approximate the carbonization process, and various theoretical models have been obtained. There are also many studies aimed at the factors that affect carbonization, and the degree of their influence, especially when using computer technology to study the carbonization problem, and directly coupling a variety of factors into a major coefficient, this method is more intuitive. Also has the remarkable effect and the result. Based on the existing concrete carbonation models and related research conclusions, this paper starts from various theories related to concrete carbonation. This paper focuses on the comprehensive analysis of concrete box girder structure, especially the mechanical properties of concrete box girder, and makes a rapid carbonation test on concrete box girder model, and probes into the influence of the special structure of concrete box girder on carbonization. With the help of finite element software and APDL program, the box girder model is simulated numerically. At the same time, combined with the results of carbonization test and numerical simulation, the numerical model is calibrated, and it is proved that it is reliable and effective to study the carbonation problem of concrete in this way. The results show that the carbonation depth of the concrete in the outer corner is the largest, 1.56 times that of the non-angle concrete, and about 2 times that of the inner corner concrete. The carbonation of the flange end region is a simple one-dimensional carbonation in the early stage. As the reaction progresses to the late stage, the carbonation depth of the upper and lower edges of the roof reaches to the concrete interior. The carbonation behavior of concrete box girder in natural environment is analyzed numerically under stress conditions. Because of the low concentration of CO2 in the natural environment, the carbonation reaction of concrete takes a long time. For the premise that we need to draw the research conclusion in a relatively short time and guide the practice, the long-term exposure test has great limitations. Therefore, the advantages of numerical analysis in carbonation are obvious. The distribution law of carbonization depth on the section of box girder is obtained, and the time required to reach the thickness of the protective layer of concrete box girder is predicted. The results show that the external corner of the concrete box girder under the stress state and the non-stress state is the area most affected by the carbonization, and the carbonation reaction rate is higher than that in the other parts.
【學(xué)位授予單位】：蘭州交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：U445.57

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