马鞍山长江公路大桥混凝土结构施工期裂缝控制研究

发布时间：2018-01-06 23:10

本文关键词：马鞍山长江公路大桥混凝土结构施工期裂缝控制研究　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：现代社会随着混凝土技术的普遍应用,混凝土开裂问题越来越受到工程界的重视,尤其是施工期裂缝,已成为混凝土的结构一个重要研究方向。本文依托“马鞍山长江公路大桥混凝土施工期裂缝收缩研究”西部课题为背景。针对混凝土结构工程早期裂缝的发展机理,通过理论分析、试验研究及数值模拟,论证了目前混凝土施工期裂缝主要由混凝土早期收缩及温度引起。本文内容包括：混凝土早期收缩试验、水泥水化热试验及桥塔水化热模拟,总结了混凝土早期收缩和水化热对施工期裂缝的影响规律,并提出相应的改善或抑制措施。具体工作和研究成果如下：1)对混凝土施工期裂缝进行理论分析,说明施工期裂缝的产生主要由早期收缩和温度引起,分别介绍了早期收缩和温度对混凝土施工期裂缝的影响。另外还查阅分析对比了6种混凝土早期收缩预测模型。2)采用自制的混凝土早期收缩试验装置,对4个混凝土收缩试块的早期收缩性能进行测试分析,试块的收缩应变测量从拆模时开始测量,一直持续到30天龄期。针对混凝土收缩大小、粉煤灰对混凝土收缩的影响及钢筋对混凝土收缩的抑制,开展试验研究及理论分析,并将试验值与理论值做了对比,从而深入地认识混凝土早期收缩机理。3)关于水化热对混凝土早期收缩影响的研究,本文对此进行了较为系统的研究。为此对普通水泥和添加粉煤灰的水泥做了水化热试验,并绘制对比了两种水泥试样的水化热生热率曲线,另外根据实测水化热曲线,拟合了能够反映水化放热速率上升与下降规律的对数正态分布公式,拟合的对数正态分布公式比目前既有的一些经验公式更能反映水化热的真实放热过程。4)利用ANSYS有限元软件模拟根据桥塔施工方法,找出结构中最不利位置。将桥塔划分为41个混凝土施工节段,利用ANSYS数值模拟了桥塔施工过程中每节段前三天的温度及应力场分布,并找出了桥塔节段施工过程中最容易出现裂缝的位置。5)整理了马鞍山长江公路大桥桥塔的施工方法,着重考察温湿度、钢筋、保护层厚度、模板、拆模时间及养护方法。根据整理的内容,总结一些导致施工期裂缝的原因,提出一些控制施工期裂缝的措施和建议。
[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.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U445.57

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