带角部增强的CFRP约束混凝土方柱抗压性能试验研究

发布时间：2018-07-15 13:18

【摘要】：CFRP约束混凝土结构是近年来备受关注的一种新型组合结构,以其轻质高强的特性、简单便捷的施工方式和经久耐用的优点受到越来越广泛的应用。目前,对于CFRP约束圆柱的研究和应用已较为成熟,但对于CFRP约束方柱而言,由于在柱角部存在应力集中的问题,导致CFRP产生的侧向约束应力不均匀,大大影响了约束效应,这一直是研究与应用的难点。很多研究表明,此类问题不是单纯的增加CFRP约束层数就能解决的。针对此问题,本文通过增加特定的局部约束来削减CFRP约束矩形柱角部应力集中带来的影响,从而通过少数约束材料的增加极大的提高整个约束柱的承载能力。具体做法是在普通CFRP约束混凝土方柱基础上,在角部以特定的方式额外黏贴局部CFRP增强层,角部增强层通过环氧树脂相互粘结形成整体共同受力。通过这一方法可以有效提高约束柱的约束效应,具有良好的应用前景。本文涉及到的研究参数有4个,分别为:局部增强层层数、局部增强层黏贴方式、局部增强层厚度和局部增强层搭接长度。以期通过对这些变量的研究找到最佳的约束形式。具体工作和研究成果如下:1)本文共设计了8组方柱试件,每组3个,尺寸均为300?300?600mm,角部带有30mm的预制倒角,混凝土强度等级均为C30。每组试件分别采用不同的约束形式,并对其进行静力轴压试验,试验测量了每组约束柱的轴向抗压强度、轴向应变和环向应变。通过研究发现,局部增强层确能明显提高约束柱的承载力,在破坏模式、CFRP环向应变分布和延性方面也均有所改善。2)局部增强层层数对约束柱的约束效应有明显影响。随着局部增强层层数的增加约束柱的抗压强度不断增大,破坏点由角部移到面部,CFRP环向应变分布发生明显变化,柱子延性也随之提高。3)局部增强层黏贴方式对约束柱的约束效应也比较明显,总体来说,内嵌“W+1+W”形式的约束效应优于外贴“1+W”形式。而局部增强层厚度和搭接长度对约束柱的约束效应不是影响很明显。增强层厚度增加一倍,抗压强度仅提高3%;当搭接长度超过40mm后,约束效应基本不变。通过分析比较,本文得出了最有效的约束形式,即夹心饼干“W+1+W+1+W+……”形式,以这种形式进行局部增强,既经济又高效。4)本文用有限元模型对实验数据进行了模拟,验证了模型的可靠性,并对其他参量进行了模拟预测。在此基础上,结合前文试验结论,得出了抗压强度设计公式,此公式与本文试验结果及有限元模拟结果吻合良好且偏安全。
[Abstract]:CFRP confined concrete structure is a new type of composite structure which has been paid more and more attention in recent years. It is more and more widely used for its light-weight and high-strength characteristics, simple and convenient construction method and durable advantages. At present, the research and application of CFRP confined cylinders have been mature, but for CFRP confined square columns, due to the problem of stress concentration at the corner of the column, the lateral confinement stress produced by CFRP is not uniform, which greatly affects the confinement effect. This has always been a difficult point in research and application. Many studies show that this kind of problem can not be solved simply by increasing the number of CFRP constraint layers. To solve this problem, the influence of stress concentration at the corner of rectangular column constrained by CFRP is reduced by adding specific local constraints, and the bearing capacity of the whole confined column is greatly improved by the increase of a few confined materials. On the basis of common CFRP confined concrete square columns, the local CFRP reinforcement layer is added to the corner in a specific way, and the corner reinforcement layer binds to each other through epoxy resin to form a common force. This method can effectively improve the constraint effect of the confined column, and has a good application prospect. There are four research parameters involved in this paper: the number of local enhancement layers, the adhesion mode of local enhancement layer, the thickness of local enhancement layer and the overlap length of local reinforcement layer. In order to find the best form of constraint through the study of these variables. The concrete work and research results are as follows: (1) in this paper, 8 groups of square column specimens are designed, each group has 3 specimens, each group is 300 ~ 300 ~ 600mm in size, corner is prefabricated chamfer with 30mm, and concrete strength grade is C30. The axial compressive strength, axial strain and circumferential strain of each group of confined columns were measured by static axial compression test. It is found that the bearing capacity of confined columns can be obviously increased by local strengthened layers, and the circumferential strain distribution and ductility of CFRP are also improved in failure mode. 2) the number of local strengthened layers has a significant effect on the confinement effect of confined columns. With the increase of the number of local reinforcement layers, the compressive strength of the confined column increases continuously, and the failure point moves from angle to face, and the circumferential strain distribution of CFRP changes obviously. The ductility of the column is also increased by .3) the binding effect of the local reinforcement layer on the confined column is also obvious. In general, the constraint effect of the embedded "W 1 W" form is better than that of the external "1 W" form. However, the thickness of local reinforcement layer and the length of lap joint have no obvious influence on the confinement effect of confined columns. The thickness of the reinforced layer is doubled, and the compressive strength is only increased by 3. When the lap length exceeds 40mm, the constraint effect is almost unchanged. Through analysis and comparison, the most effective constraint form is obtained, that is, the sandwich biscuit "W1 W1W." In this paper, the finite element model is used to simulate the experimental data, the reliability of the model is verified, and the other parameters are simulated and forecasted. On this basis, combined with the previous experimental results, the design formula of compressive strength is obtained. The formula is in good agreement with the experimental results and the results of finite element simulation in this paper.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU375.3

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