预应力碳纤维片材加固混凝土梁胶层粘结厚度的影响试验研究

发布时间：2018-01-17 16:09

  本文关键词：预应力碳纤维片材加固混凝土梁胶层粘结厚度的影响试验研究　出处：《长沙理工大学》2014年硕士论文　论文类型：学位论文

  更多相关文章： 预应力 碳纤维片材 加固 混凝土梁 胶层厚度 界面粘结应力

【摘要】：我国地域辽阔,国家对基础建设投入不断加大,服役桥梁数量的不断增加,同时我国交通量不断攀升、自然环境、结构本身老化等因素导致在役桥梁承载能力难以满足实际要求,对在役桥梁进行加固已成为重要研究课题。采用新材料与新工艺对结构进行加固是研究的主流,运用预应力FRP加固既有结构,不仅充分发挥FRP材料轻质、高强、抗腐蚀等材料特性,而且能较好的提高被加固结构的承载能力、改善被加固结构的工作性能、对被加固结构自重影响较小等优点。而针对预应力CFRP板材加固混凝土梁在不同初始应力条件下胶层粘结厚度对被加固结构截面应力、CFRP板材放张后界面应变分布与CFRP板材界面应力分布的影响的研究较少；在此背景下,本文通过采用9片预应力CFRP板材加固混凝土梁,初始应力为CFRP板材抗拉极限承载力的10%、20%与30%,胶层粘结厚度分别为2mm、4mm与6mm条件下,对以上问题进行试验研究,研究表明：1.胶层粘结厚度对预应力CFRP板材加固混凝土梁混凝土截面应力影响较小,可采用混凝土梁偏心受压的计算方法对放张后混凝土梁跨中截面应力分布情况进行计算。2. CFRP板材界面应变分布沿板端逐渐增大,当达到一定粘结长度时板材的应变趋于稳定且与初始应变接近,通过对CFRP板材界面应变数值拟合得到每片梁CFRP板材界面应变的分布情况；提出临界初始应力的定义,初始应力达到某一定值时板材界面应变影响长度急剧增加,该定值为临界初始应力；不同胶层粘结厚度临界初始应力不同。3.环形碳纤维布锚固梁端在锚固处形成界面阻力使锚固处CFRP板材界面应力小于临近锚固处的界面应力；环形端锚对临近锚固处的CFRP板材界面应力造成界面应力滞后现象。4.相同胶层粘结厚度CFRP板材界面粘结应力-放张力间具有相同数值关系,通过对试验数据进行数值回归得到不同胶层粘结厚度的CFRP板材界面粘结应力-放张力计算式；该计算式分为非线性上升段与非线线下降段,不同胶层粘结厚度具有不同的最大CFRP板材界面粘结应力；试验表明胶层粘结厚度为4mm最为合适,采用外贴CFRP板材加固混凝土结构具有一定参考价值。
[Abstract]:Our country has a vast territory, the national investment in infrastructure is increasing, the number of service bridges is increasing, at the same time, the traffic volume of our country is rising constantly, and the natural environment. Due to the aging of the structure itself, the bearing capacity of existing bridges is difficult to meet the actual requirements. Strengthening existing bridges has become an important research topic. It is the mainstream of research to use new materials and new technology to strengthen the structure. Using prestressed FRP to strengthen the existing structure, not only give full play to the lightweight, high strength, corrosion resistance and other material characteristics of FRP, but also can improve the bearing capacity of the strengthened structure. Improve the working performance of reinforced structures. It has little influence on the self-weight of reinforced structure, but the bond thickness of adhesive layer on the section stress of strengthened structure under different initial stress conditions is aimed at the prestressed CFRP plate strengthened concrete beam under different initial stress conditions. The influence of strain distribution at the interface of CFRP sheet and the stress distribution at the interface of CFRP sheet is less studied. In this context, 9 pieces of prestressed CFRP plates are used to strengthen concrete beams. The initial stress is 10% and 30% of the ultimate tensile capacity of CFRP plates. When the adhesive thickness of the adhesive layer is 2 mm and 6 mm respectively, the above problems are studied experimentally. The results show that the thickness of adhesive layer has little effect on the section stress of concrete beam strengthened with prestressed CFRP plate. The calculation method of eccentric compression of concrete beam can be used to calculate the stress distribution of the cross section of concrete beam after stretching. 2. The strain distribution at the interface of CFRP plate increases gradually along the end of the slab. When the bond length is reached, the strain of the plate tends to be stable and close to the initial strain. The distribution of the strain at the interface of the CFRP plate is obtained by the numerical fitting of the interfacial strain of each beam. The definition of critical initial stress is put forward. When the initial stress reaches a certain value, the influence length of the interfacial strain on the plate increases sharply, which is the critical initial stress. The critical initial stress of different adhesive thickness is different. 3. The interfacial stress of CFRP plate in Anchorage is smaller than that near Anchorage due to the interfacial resistance formed at the end of annular CFRP Anchorage. The interfacial stress hysteresis phenomenon caused by the annular end anchor on the CFRP plate near the Anchorage. 4. There is the same numerical relationship between the interfacial bond stress and the release tension of the CFRP plate with the same adhesive thickness. The calculation formula of interfacial bond stress-release tension of CFRP plate with different adhesive thickness was obtained by numerical regression of test data. The formula can be divided into nonlinear ascending section and non-linear descending section. Different adhesive thickness of adhesive layer has different maximum bond stress at the interface of CFRP sheet. The test results show that the adhesive thickness of the adhesive layer is 4 mm, and it is of certain reference value to reinforce the concrete structure with the outer CFRP plate.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U445.72
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本文编号：1436961