本文關鍵詞：馬鞍山長江公路大橋混凝土結構施工期裂縫控制研究　出處：《東南大學》2015年碩士論文　論文類型：學位論文

  更多相關文章： 混凝土早期裂縫 裂縫控制 早期收縮 水化熱 收縮試驗 橋塔 施工裂縫

【摘要】：現(xiàn)代社會隨著混凝土技術的普遍應用,混凝土開裂問題越來越受到工程界的重視,尤其是施工期裂縫,已成為混凝土的結構一個重要研究方向。本文依托“馬鞍山長江公路大橋混凝土施工期裂縫收縮研究”西部課題為背景。針對混凝土結構工程早期裂縫的發(fā)展機理,通過理論分析、試驗研究及數(shù)值模擬,論證了目前混凝土施工期裂縫主要由混凝土早期收縮及溫度引起。本文內容包括：混凝土早期收縮試驗、水泥水化熱試驗及橋塔水化熱模擬,總結了混凝土早期收縮和水化熱對施工期裂縫的影響規(guī)律,并提出相應的改善或抑制措施。具體工作和研究成果如下：1)對混凝土施工期裂縫進行理論分析,說明施工期裂縫的產生主要由早期收縮和溫度引起,分別介紹了早期收縮和溫度對混凝土施工期裂縫的影響。另外還查閱分析對比了6種混凝土早期收縮預測模型。2)采用自制的混凝土早期收縮試驗裝置,對4個混凝土收縮試塊的早期收縮性能進行測試分析,試塊的收縮應變測量從拆模時開始測量,一直持續(xù)到30天齡期。針對混凝土收縮大小、粉煤灰對混凝土收縮的影響及鋼筋對混凝土收縮的抑制,開展試驗研究及理論分析,并將試驗值與理論值做了對比,從而深入地認識混凝土早期收縮機理。3)關于水化熱對混凝土早期收縮影響的研究,本文對此進行了較為系統(tǒng)的研究。為此對普通水泥和添加粉煤灰的水泥做了水化熱試驗,并繪制對比了兩種水泥試樣的水化熱生熱率曲線,另外根據(jù)實測水化熱曲線,擬合了能夠反映水化放熱速率上升與下降規(guī)律的對數(shù)正態(tài)分布公式,擬合的對數(shù)正態(tài)分布公式比目前既有的一些經驗公式更能反映水化熱的真實放熱過程。4)利用ANSYS有限元軟件模擬根據(jù)橋塔施工方法,找出結構中最不利位置。將橋塔劃分為41個混凝土施工節(jié)段,利用ANSYS數(shù)值模擬了橋塔施工過程中每節(jié)段前三天的溫度及應力場分布,并找出了橋塔節(jié)段施工過程中最容易出現(xiàn)裂縫的位置。5)整理了馬鞍山長江公路大橋橋塔的施工方法,著重考察溫濕度、鋼筋、保護層厚度、模板、拆模時間及養(yǎng)護方法。根據(jù)整理的內容,總結一些導致施工期裂縫的原因,提出一些控制施工期裂縫的措施和建議。
[Abstract]:With the widespread application of concrete technology in modern society, the problem of concrete cracking has been paid more and more attention by the engineering circles, especially the cracks during construction. It has become an important research direction of concrete structure. This paper relies on "study on shrinkage of concrete cracks in construction period of Ma'anshan Yangtze River Highway Bridge" In view of the development mechanism of early cracks in concrete structure engineering, the western project is the background. Through theoretical analysis, experimental research and numerical simulation, it is demonstrated that cracks in concrete construction period are mainly caused by early shrinkage and temperature of concrete. The content of this paper includes: early shrinkage test of concrete. Cement hydration heat test and bridge tower hydration heat simulation, summed up the early shrinkage of concrete and hydration heat on the cracks during construction. The concrete work and research results are as follows: 1) the concrete cracks during construction are analyzed theoretically, which shows that the cracks are mainly caused by early shrinkage and temperature. The effects of early shrinkage and temperature on cracks during construction are introduced respectively. In addition, six kinds of concrete early shrinkage prediction models. 2) Self-made concrete early shrinkage test device are used. The early shrinkage performance of four concrete shrinkage test blocks was tested and analyzed. The shrinkage strain measurement of the concrete blocks began from the time of mold removal and lasted until 30 days of age, aiming at the shrinkage size of concrete. The influence of fly ash on the shrinkage of concrete and the inhibition of rebar on shrinkage of concrete are studied and analyzed theoretically, and the experimental value is compared with the theoretical value. Therefore, the mechanism of early shrinkage of concrete. 3) the effect of hydration heat on early shrinkage of concrete is studied. In this paper, the hydration heat test of ordinary cement and cement with fly ash was carried out, and the curves of hydration heat transfer rate of two kinds of cement samples were drawn and compared. In addition, according to the measured hydration heat curve, the logarithmic normal distribution formula which can reflect the law of rising and decreasing of hydration heat release rate is fitted. The fitted logarithmic normal distribution formula can reflect the real exothermic process of hydration heat better than some existing empirical formulas. 4) the ANSYS finite element software is used to simulate the bridge tower construction method. In order to find out the most unfavorable position of the structure, the tower is divided into 41 concrete construction sections, and the temperature and stress field distribution in the first three days of each section is simulated by ANSYS numerical simulation. The construction method of the bridge tower of Ma'anshan Yangtze River Highway Bridge is sorted out, with emphasis on temperature and humidity, steel bar, thickness of protective layer and formwork. According to the contents of consolidation, the causes of cracks during construction are summarized, and some measures and suggestions for controlling cracks during construction are put forward.
【學位授予單位】：東南大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：U445.57

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