【作者】 李笑然；

【导师】 王元丰；

【作者基本信息】 北京交通大学 ， 结构工程， 2013， 博士

【摘要】 FRP加固混凝土已成为广泛应用的工程结构加固技术。但FRP约束混凝土作为新型组合材料,其阻尼性能的研究还处在起步阶段,在进行FRP约束混凝土结构抗震分析时,一般取其阻尼比与混凝土结构相同进行计算,这将使其动力分析结果的可靠性受到很大影响。由于机理尚不非常清楚,试验与理论研究复杂,对于FRP约束混凝土结构的阻尼目前国内外还没有专门研究、尚处空白。本文针对FRP约束钢筋混凝土及损伤钢筋混凝土材料的非线性阻尼特性进行研究。首先采用试验方法测定FRP约束钢筋混凝土柱的阻尼比以及在水平反复荷载作用下的滞回耗能性能。然后,研究考虑初始损伤以及强弱约束条件下的FRP约束钢筋混凝土柱的滞回性能和阻尼耗能特性,建立其非线性材料阻尼计算公式。基于所建的非线性阻尼模型,建立非线性阻尼系统的动力响应分析方法,对FRP约束无损伤及有损伤钢筋混凝土柱的地震响应进行分析。该项研究有助于非线性阻尼理论和FRP约束混凝土结构抗震分析理论的发展及应用。主要研究工作如下：(1)试验研究了FRP约束无损伤及不同初始损伤的钢筋混凝土柱在水平反复荷载作用下的破坏过程、滞回性能、刚度退化和耗能性能；通过模态识别方法,测试并分析了FRP约束无损伤及不同初始损伤的钢筋混凝土柱的基频、阻尼比随不同参数的变化规律。(2)利用OpenSees系统(Open System for Earthquake Engineering Simulation),采用FRP强弱约束混凝土本构模型、考虑初始损伤及损伤发展的约束混凝土本构模型及Karsan-Jirsa加卸载准则,对FRP约束无损伤及有损伤钢筋混凝土柱滞回性能进行了模拟,并将计算结果与试验结果进行了对比。(3)在Lazan对材料阻尼及应力关系研究的基础上,分别计算了FRP约束无损伤及不同初始损伤的钢筋混凝土压弯柱的单位体积损耗能量,在分析各种因素对耗能影响的基础上,通过SPSS统计分析软件回归建立了FRP约束无损伤及有损伤钢筋混凝土压弯柱的非线性阻尼理论计算公式。(4)在复阻尼动力系统内,采用有限元法,通过建立的非线性阻尼模型,迭代计算了FRP约束无损伤及有损伤的钢筋混凝土柱阻尼值及相应的动力响应,并与取常阻尼系数计算的动力响应进行了对比,定量分析了不同参数对材料阻尼及动力响应的影响规律。(5)将非线性阻尼模型引入到结构动力方程中,计算了FRP约束无损伤及有损伤钢筋混凝土柱在单、双向简谐及地震荷载作用下的动力响应,结果表明：非线性阻尼下的振动反应与常阻尼比下的振动反应有着较大的差异。从设计角度来讲,常阻尼比计算模型的分析结果将偏于不安全。同时分析了混凝土强度、纵筋率、初始损伤和FRP率对FRP约束钢筋混凝土柱阻尼和自振频率的影响。更多还原

【Abstract】 Externally wrapping fiber-reinforced polymer (FRP) composites has gotten increasingly wide applications in strengthening and retrofitting of existing concrete structures. However, as a new kind of composite material, the study for material damping of FRP-confined concrete is still in the initial stage. In the seismic analysis of FRP-confined reinforced concrete (RC)structures, the constant damping ratio of general RC structures, instead of a proper damping value, is usually adopted at present due to the complexity in mechanism and the difficulty in experiment, which, greatly affects the reliability of the dynamic analysis results. The proper damping model of FRP-confined RC structures has not yet been set up.This paper aims to explore into the non-linear damping characteristics of FRP-confined RC and damaged RC materials. Firstly, a series of tests are conducted to observe the damping and hysteretic energy dissipation of FRP-confined RC columns. Subsequently, hysteretic performance and hysteretic energy dissipation characteristics of FRP-confined RC columns are investigated considering initial damage and different confinement levels to establish the non-linear damping formulas. Finally, based on the proposed damping models, an improved method for dynamic analysis considering non-linear damping is developed to analyze the seismic response of FRP-confined RC and damaged RC columns. This study is helpful to the development and application of non-linear damping theory and anti-seismic analysis theory of FRP-confined RC structures. Main researching works of this dissertation are as following:(1) Test process is designed to study the hysteretic performance of FRP-confined RC and damaged RC columns, and carrying capacity decline and stiffness degenerate of FRP-confined concrete under cyclic loading. By using the modal identification method, the effects of different parameters on the natural frequencies and damping ratio of FRP-confined RC columns are tested and analyzed.(2) FRP-confined concrete constitution models considering initial damage and different confinement levels and Karsan-Jirsa unloading-reloading law are utilized to compute the hysteretic performance of FRP-confined RC and damaged RC columns subjected to compression and bending by the OpenSees program. The results of program are in good agreement with the experimental results.(3) Based on the study for the relation between material damping and stress of Lazan, the energy dissipation of FRP-confined RC and damaged RC columns are computed. Further, the effect of a few parameters on energy dissipation is analyzed, and the non-linear damping formulas of FRP-confined RC and damaged RC columns subjected to compression and bending are set up by non-linear regression with a commercial software SPSS.(4) Based on the proposed damping models, Finite Element Method is adopted to obtain the real material damping values and corresponding dynamic responses of FRP-confined RC and damaged RC columns iteratively in dynamic system with hysteretic damping, and the results are compared with the dynamic responses by constant material damping. Influencing law of parameters on the material damping and dynamic responses is analyzed quantitatively.(5) By introducing the the non-linear damping models into the structural dynamic equation, the responses of FRP-confined RC and damaged RC columns under the uniaxial and biaxial harmonic and earthquake loadings are calculated, the analytical results indicate that there are remarkable differences between the dynamic response based on non-linear damping and constant damping. In view of design, the seismic response level based on constant damping recommended by current code for seismic design of FRP-confined RC component may be significant underestimate. The effects of the concrete strength, longitudinal reinforcement ratio, initial damage level and FRP volume ratio on the damping and natural frequencies time history of FRP-confined RC columns are analyzed.更多还原