PVA-ECC钢筋网外包RC梁抗剪试验研究

发布时间：2018-12-12 03:51

【摘要】：随着我国现代建筑施工技术水平的不断提高,混凝土结构加固技术得到了较快的发展,积累了较丰富的实践经验。人们在关心建筑结构经过加固改造后达到安全可靠的前提下,也越来越重视建筑结构后期的使用性、耐久性和经济性。PVA-ECC钢筋网加固混凝土结构的优越性通过本次试验研究得到了充分的体现,希望这种加固方法能更多的应用到实际工程中去。PVA-ECC是一种水泥基复合材料,掺入的PVA是一种高强高弹的纤维,PVA-ECC开裂时的裂缝表现出明显的“细而多”现象,破坏时的变形也较大,此外,PVA-ECC还具有良好的耐久性及抵抗温湿交替作用的能力。目前这种加固方法存在的主要问题就在于它的施工成本较高,PVA纤维本身的价格较贵,随着社会经济的发展,相信这种加固方法会得到更广泛的应用。PVA-ECC钢筋网外包钢筋混凝土结构法的实质是:首先,在原结构表面进行凿毛处理和植入一定数量的剪切销钉等界面处理,以增强PVA-ECC钢筋网加固层与原构件的界面粘结强度,使之能与原构件共同受力、协调变形;然后,在处理好的结构界面上按设计的钢筋类别、直径和间距要求绑扎钢筋网骨架;最后,直接涂抹或者通过支设简单的模板浇筑一薄层PVA-ECC,经规定的时间养护后达到其设计强度值即可。该加固法中,PVA-ECC不仅具有较高的抗压和抗拉强度以抵抗荷载作用,还能作为原结构的保护层;而钢筋网骨架本身作为主要受力构件的同时,还能对原结构形成有效的套箍作用,能有效抑制原结构斜裂缝的开展。该加固法操作简单、可靠,且适用于绝大多数的结构构件加固。本次试验共设计和制作了带悬臂的钢筋混凝土梁4根,其中原对比梁2根和采用PVA-ECC钢筋网抗剪加固梁2根,加固梁采用四面围绕加固。根据剪跨比不同将试件分为两组,通过试验测得两组试件在支座及两个集中力作用点处的挠度,原梁箍筋应变、加固箍筋应变、原梁混凝土应变和加固梁复合砂浆层应变,结合斜裂缝开展、破坏形态对试验结果进行分析研究,得到了加固梁抗剪承载能力随剪跨比不同而变化的规律以及影响其抗剪承载能力的其他因素,结果表明:加固梁的截面刚度和抗剪承载力较对比梁均有一定的提高,且剪跨比越大,提高的幅度也越大;试验梁加固箍筋的配置情况和加固复合砂浆层的强度等级是影响其抗剪承载能力的主要因素。为了方便工程施工和设计人员直接应用,根据桁架-拱模型原理,给出加固梁理论的抗剪承载能力计算公式,对比发现,公式计算值与试验特征荷载值吻合良好。最后,通过非线性有限元分析软件ANSYS对4根试验梁进行模拟计算,模拟计算结果与试验结果及现象吻合良好,进一步验证该加固方法的有效性。
[Abstract]:With the development of modern construction technology in our country, the reinforcement technology of concrete structure has developed rapidly and accumulated rich practical experience. People pay more and more attention to the later use of the building structure on the premise that the building structure is safe and reliable after the reinforcement and transformation. Durability and economy. The superiority of reinforced concrete structure strengthened with PVA-ECC steel mesh has been fully demonstrated by this experimental study. It is hoped that this reinforcement method can be more applied to practical engineering. PVA-ECC is a kind of cement matrix composite material, and the doped PVA is a kind of fiber with high strength and high elasticity. The cracks of PVA-ECC show a "fine and many" phenomenon. In addition, PVA-ECC also has good durability and resistance to the alternating action of temperature and humidity. At present, the main problem of this reinforcement method is that its construction cost is high, the price of PVA fiber itself is more expensive, and with the development of social economy, It is believed that this reinforcement method will be applied more widely. The essence of PVA-ECC reinforcement mesh outlay reinforced concrete structure method is as follows: firstly, the surface of the original structure is treated with hair-cutting and a certain number of shear pins. In order to strengthen the interfacial bond strength between the PVA-ECC reinforcement layer and the original member, it can work together with the original member and coordinate the deformation. Then, according to the designed steel bar category, diameter and spacing, the steel mesh skeleton is bound on the processed structural interface. Finally, the design strength of PVA-ECC, can be reached by directly smearing or pouring a thin layer of PVA-ECC, with a simple template for a specified time of curing. In this method, PVA-ECC not only has high compressive and tensile strength to resist the load, but also can be used as the protective layer of the original structure. As the main force member, the steel mesh skeleton can also form an effective clamping effect on the original structure and restrain the development of the oblique crack of the original structure effectively. The reinforcement method is simple, reliable and suitable for most structural members. Four reinforced concrete beams with cantilever were designed and manufactured in this experiment. Among them, 2 original contrast beams and 2 reinforced concrete beams strengthened by PVA-ECC steel mesh were strengthened around four sides. According to the different shear span ratio, the specimens are divided into two groups. The deflection of the two groups of specimens at the support and two concentrated force points, the stirrups strain of the original beam, the strain of the reinforcement stirrups, the strain of the concrete of the original beam and the strain of the composite mortar layer of the strengthened beam are measured. Based on the analysis of the experimental results with the development of oblique cracks and failure patterns, the variation of shear bearing capacity of strengthened beams with different shear span ratio and other factors affecting the shear bearing capacity of strengthened beams are obtained. The results show that the cross-section stiffness and shear bearing capacity of the strengthened beams are higher than those of the contrast beams, and the larger the shear span ratio is, the greater the range is. The configuration of stirrups strengthened by test beams and the strength grade of reinforced composite mortar layer are the main factors affecting its shear bearing capacity. In order to facilitate the direct application of engineering construction and design personnel, according to the principle of truss-arch model, the calculation formula of shear bearing capacity of strengthened beam theory is given. By comparison, it is found that the calculated value of the formula is in good agreement with the experimental characteristic load value. Finally, four test beams are simulated and calculated by nonlinear finite element analysis software ANSYS. The simulation results are in good agreement with the experimental results and phenomena, which further verify the effectiveness of the reinforcement method.
【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】：TU375.1

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