Establishment of strengthening technique for concrete structures with externally bonded Carbon Fiber Sheets

外粘碳纤维布加固混凝土结构技术的建立

基本信息

批准号：
08555107
负责人：
WU Zhishen
金额：
$ 4.22万
依托单位：
Ibaraki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08555107/
关键词：
Concrete Structures FRP Sheet-Strengthening Method Design of Debonding Shear Strengthening Fracture Mechanics Analysis Finite Element Analysis Effectiveness of Crack Control Durability Assessment 耐震補強工法炭素繊維シート剥離破壊破壊力学的構造解析法複合補強

项目摘要

As the research result,1) The failure mechanism and reason of damaged reinforced concrete structures by Hyogoken-Nanbu earthquake is investigated by focusing on brittleness transition due to the high strain rates and size affect. Firstly, a finite element formulation is developed by installing both rate-dependent smeared crack model and viscoplastic models. Secondly, in order to remove some drawbacks of smeared crack models, a mixed finite element method for composite discontinuous analysis is proposed. The simulation results with these FEM models show the possibility of a transition in the mode of failure from flexural to a more brittle, share type of failure. And failure of structures that exhibit a share-dominated behavior can be expressed well by the proposed finite element models.2) Applicabilities of existing reinforced concrete design method, and a simple strain compatibility methods to FRP-strengthened structures are investigated. The following collapse mechanism are identified … More and analyzed : steel yield-FRP rapture, Steel yield-concrete crushing, compressive failure, share failure and different debonding failures.3) Facing on the facts that 1) the bond betweet the composite sheet and the concrete may fracture in a sudden manner as the result of the catastrophic propagation of a crack along the FRP-concrete interface ; 2) less or no frictional behavior along the FRP-concrete interface can be observed, which may be different from the bond-slip behavior between concrete and reinforcing bars, bonding model, including bond stress-slip relationship is proposed. And the critical strain energy release rate (interfacial fracture energies) for the interface for mode I,mode II and mixid mode (peeling-off) is also discussed. The values are measured using double-shear specimens pulled in tension.A analytical model, so called fracture energy approach, is developed based on the concept of fracture mechanics. Moreover, a series of experimental investigations of RC tensile members strengthened by carbon fiber sheets is performed. The variables included two types of CFRP materials with high strength and high modulus, different strengths of concrete, different reinforcing ratios of rebars, and different layrs of FRP sheets. A lot of essential findings, such as the minimum cracking spacing and crack distribution characteristics, superiority of sheet stress of crack width, and debonding length etc.are conducted firstly by this experimental program. The experimental results is also used to calibrate the several material parameters.5) As a general numerical model, the finite element model proposed in 1) is developed to evaluated the load-carrying capacity and deformation behavior of FRP sheet-strengthened concrete of RC structures with different failure modes, such as flexural failure, shear failure and debonding failures. The ultimate behavior for different structural members such as beams, columns and tunnels etc, can be expressed well by the model. Finally, a design strategy integrating the properties of CFRP sheets and composite structural behavior is recommended to effectively and efficiently utilize the CFRP sheets.6) The durability of FRP sheet-concrete interface in FRP-strengthening method is investigated by a series of experimental program with different environment actions, surface behavior, types of epoxy and concrete qualities.7) A design concept for debonding failure as one of design indices is suggested.The theoretical system constructed through this research is considered to be rational and will be developed in future research effort. The achieved new findings is considered to be useful for establishment of a rational design code. Less

作为研究结果，1）由于高应变速率和大小影响，研究了北鸟地震损坏的钢筋混凝土结构的破坏机制和原因。首先，通过安装依赖速率的涂片裂纹模型和粘塑性模型来开发有限元公式。其次，为了删除涂抹裂纹模型的一些缺点，提出了一种混合有限元方法，用于不连续分析。这些FEM模型的仿真结果显示了从柔性到更脆的，共享的失败类型的失败模式下过渡的可能性。通过提出的有限元模型可以很好地表达暴露于股票主导行为的结构的失败。2）现有的钢筋混凝土设计方法的适用性，并研究了一种简单的应变兼容方法，用于frp加长结构。确定了以下倒塌机制……更多和分析：钢铁产量 - frp曲折，钢屈服 - 纠结破坏，压缩故障，股份失败和不同的剥离失败。3）面对以下事实，即1）复合纸和混凝土之间的键可能会突然以灾难性的速度沿frp-concroph的结果而突然地分裂。 2）可以观察到沿FRP - 混凝土界面的较少或没有摩擦行为，这可能与混凝土和加固条之间的键滑行为不同，粘合模型（包括粘合模型，包括粘合应力滑移关系）。还讨论了模式I，模式II和MIXID模式（剥落）的界面的临界应变能释放速率（界面断裂能）。使用张力中拉动的双剪切标本测量值。一个分析模型，所谓的断裂能量方法是根据断裂机制的概念开发的。此外，还进行了一系列对通过碳纤维板增强的RC拉伸成员的实验研究。这些变量包括具有高强度和高模量的两种类型的CFRP材料，混凝土的不同强度，不同的钢筋增强比和不同的FRP板。首先，该实验程序首先进行了许多基本发现，例如最小开裂间距和裂纹分布特征，裂纹宽度的优越性以及脱衣长度等。实验结果还用于校准多个材料参数。5）作为一个通用数值模型，开发了1）中提出的有限元模型来评估RC结构的负载能力和使用不同故障模式的RC结构的载荷能力和变形行为，例如弯曲失败，剪切故障，剪切故障，剪切故障，剪切失败和删除失败。模型可以很好地表达出不同结构构件（例如梁，柱和隧道等）的最终行为。最后，建议将整合CFRP表格和复合结构行为的特性的设计策略有效，有效地利用CFRP表。6）6）通过一系列实验性计划，表面行为，表面行为，质量构成了设计的概念。通过这项研究构建的系统被认为是理性的，并且将在未来的研究工作中发展。实现的新发现被认为对建立合理的设计代码很有用。较少的