【作者】 周昊；

【导师】 黄培彦；

【作者基本信息】 华南理工大学 ， 固体力学， 2012， 博士

【摘要】 纤维增强复合材料（FRP）加固钢筋混凝土（RC）结构的耐久性是土木建筑领域的前沿课题。本文以亚热带在役RC桥梁为应用背景，采用本课题组发明的新型FRP片材——碳纤维薄板（CFL），构建CFL加固RC构件，并以此为研究对象，考虑我国南方和沿海等地区的湿热大气环境、以及公路运营桥梁的实际车辆荷载，探讨了在湿热环境与车辆荷载的共同作用下采用CFL加固RC构件的耐久性实验方法问题，研制和集成了能够实现上述构件耐久性实验方法的实验系统，并对该实验方法的有效性和可行性进行了实验验证。本文的主要研究内容及结论如下：1、针对结构耐久性实验的瓶颈问题——环境与载荷的共同作用问题，提出了“湿热环境与实际车辆荷载共同作用下桥梁结构耐久性的加速实验方法”。该方法具有以下特点：a）解决了现有同类构件耐久性实验无法实现湿热环境与动载荷的共同作用问题；b）能实现温度、湿度与载荷的同步循环或不同步循环作用。其中，环境温度的变化范围为5℃~50℃；环境湿度的变化范围为65%~98%RH；c）能真实地再现亚热带运营桥梁的工作条件（温度、湿度和载荷条件）；d）车辆载荷谱是分别对国道或高速公路的车流量经过数据采集、统计分析、数值模拟以及实验谱编制而成；e）环境与载荷的加速方式能再现它们对构件的作用效应。2、为了能实现湿热环境与实际车辆荷载共同作用下桥梁结构的耐久性实验，本研究研发和集成了相应的实验系统。该系统分为两部分：a）桥梁工作环境模拟实验系统；b）能够模拟车辆随机载荷的加载及测试系统。其中，环境模拟实验系统的功能及技术特点为：能实现本研究及后续研究所需要的湿热循环、温度-海水环境、冻融环境、干湿循环等实验环境的模拟；所有技术指标不低于现有同类产品；能满足较大尺寸的桥梁结构模型试件实验之需要；能与加载及测试系统相配套。加载及测试系统由原有的MTS810实验系统经改装而成。车辆随机载荷谱系采用自编的软件模拟后再输入到实验系统的控制器内。经过近1年时间的调试运行和市计量局的标定检验、以及2种湿热环境与实际车辆荷载共同作用下FRP加固RC梁的耐久性实验，证实了该系统的可行性、稳定性和可靠性。3、利用上述实验系统，实施了湿热环境下FRP加固RC梁的四种耐久性实验：a）恒定环境与常幅疲劳载荷的非共同作用实验，即将试件作环境处理后再施加常幅疲劳载荷（现行规定方法）；b）恒定环境与常幅疲劳载荷共同作用下的实验；c）实际环境与常幅疲劳载荷共同作用下的实验；d）实际环境与车辆随机载荷共同作用下的实验。在相同的应力水平下，第a）与第b）种实验结果、第b）与第c）或第d）种实验结果的对比分析、以及构件耐久性破坏机理分析结果表明，实验方法对构件耐久性有显著的影响，而且共同作用下构件的耐久性较差。这表明按照现行规范规定的非共同作用的实验方法所推定的构件耐久性比实际工作条件下桥梁结构件的好，这将导致其耐久性设计偏于危险。同时，这也说明了桥梁结构耐久性实验采用环境与车辆载荷共同作用的实验方法的重要性，并证明了本文提出的耐久性实验方法是有效和可行的。4、对四种湿热环境下CFL加固RC梁的破坏模式、刚度衰减规律、挠度曲线和S~N曲线的分析结果表明：a）随着温度和湿度的升高，加固梁的界面破坏层也会变化，从低温低湿时的混凝土层逐渐向胶层与混凝土表层的交界处转移，高温高湿时在胶层发生破坏。与此相对应，加固梁的破坏模式也逐步变为单一模式，即碳纤维薄板的剥离破坏；b）在环境与疲劳荷载共同作用下加固梁的刚度衰减速率比相同湿热条件下非共同作用下的要快，而且，在实际湿热环境与常幅疲劳荷载共同作用下，加固梁的刚度曲线与输入的温度湿度曲线相关，并与输入曲线呈相同的变化趋势；c）对于本文所示的各种环境下的加固梁，建立了其挠度f与相对疲劳寿命ln n/lnNj的关系曲线方程；对于湿热循环与疲劳荷载共同作用下的加固梁，则建立了动态割线刚度的疲劳寿命方程。这为湿热环境条件下CFL加固RC梁的疲劳寿命分析奠定了良好基础；d）不同实验条件下得到的S~N曲线，再次表明了耐久性实验方法对试验梁环境疲劳寿命/耐久性的影响是显著的，而本文提出的耐久性实验方法是必需的、有效的和可行的。更多还原

【Abstract】 Durability of reinforced concrete (RC) structures strengthened with fiber reinforcedpolymer (FRP) is the forefront topic in field of civil engineering. In this paper, existing RCbridges in subtropical environments were taken as the application background. Using CarbonFiber Laminates (CFL) developed by this project team, RC beams strengthened with CFLwere constructed and were taken as the research objects. Considering the hot and humidenvironment in South China and coastal areas and actual vehicle loads on highway bridges inoperation, durability experimental method of RC beams strengthened with CFL underhygrothermal environment and vehicle load coupling was discussed. Experimental systemwhich achieved the above durability experiment method was integrated and developed. Theeffectiveness and feasibility of the experiment method were later verified by differentexperiments.1. Against the environment and load coupling problem which is the bottlenecks ofstructure durability experiments, durability acceleration experiment method of bridgestructure under hygrothermal and actual vehicle load coupling was proposed, which has thefollowing innovations: a) the hygrothermal environment and dynamic load coupling problemsin durability experiment were solved; b) synchronous cycles or non-synchronized cycles oftemperature, humidity and load were achieved, where, environment temperature range was5℃~50℃and environment humidity range was65%~98%RH; c) working conditions(temperature, humidity and load conditions) of bridges in operation in subtropicalenvironments were faithfully reproduced; d) vehicle load spectrum was established fromnational highway or freeway traffic flow through data acquisition, statistical analysis,numerical simulation and experimental spectra calculation; e) the accelerated way ofenvironment and load coupling reproduced the effects on the components.2. In order to establish durability experiment of bridge structure under hygrothermalenvironment and actual vehicle load coupling, corresponding experimental system wasintegrated and developed, which composed of two parts: a) bridge working environmentsimulation experiment system; b) random vehicle loads simulation experiment system. Thefeatures of environment simulation experiment system were: experimental environmentsimulations of thermal and humidity cycle, temperature-marine environment, freeze-thawenvironment, wet and dry cycle were achieved; All technical indicators were not less than theexisting similar products; the needs of the larger size of the bridge structure model testexperiment were meet; environment system was matched with the load and test systems. Load and test system were upgraded from MTS810. Random vehicle loads were simulated bysoftware and then inputted to the controller of the experimental system. After debugging andrunning for nearly a year, this system passed the calibration test from the Municipal Bureau ofWeights and Measures. Two kinds of durability test of FRP strengthened RC beam underthermal and humid environment and the actual vehicle load coupling were carried out.Feasibility, stability and reliability of the system were confirmed.3. Using the above experimental system, four kinds of durability experiments of RCbeams strengthened with FRP were carried out; a) constant environment and constantamplitude fatigue loading non-coupling experiment, in which specimens were environmenttreated first and then imposed with constant amplitude fatigue load; b) constant environmentand constant amplitude fatigue loading coupling experiment; c) actual environment andconstant amplitude fatigue loading coupling experiment; d) actual environment and randomvehicle loading coupling experiment. In the same stress level, experiment results of a) and b),b) and c), b) and d) were compared and failure mechanism of components was analyzed.Results showed that the experiment method had a significant impact on the durability ofcomponents. Durability of components in coupling condition was worse and the worst inrandom vehicle load and environment coupling condition. This indicated that the durability ofbridge structure components determined by non-coupling experiment method in specificationswas less conservative than in actual conditions, which lead durability design to be somewhatdangerous. At the same time, it also showed the importance of using the experimental methodof random vehicle load and environment coupling in a bridge structure durability experimentsand proved the effectiveness and feasibility of durability experiment method proposed in thispaper.4. Analysis results of fatigue failure modes, stiffness degradation, deflection curves andS~N curves of RC beams strengthened with FRP in hygrothermal environment indicated that:a) Destruction layer in interface was moving from concrete layer to adhesive layer, with theincrease affect of temperature and humidity, destruction was eventually occurred in theadhesive layer. Fatigue failure mode types were reduced by influence of hygrothermalenvironment. As the hygrothermal environment continued affecting, fatigue failure modebecame singularity, which FRP debonding failure became the only failure mode. b) Stiffnessdegradation of strengthened beams in coupling condition was faster than that in non-couplingcondition. This showed hygrothermal environment had a great impact on the stiffnessdegradation of strengthened beams. In actual environment and constant amplitude fatigue loadcoupling, stiffness degradation of strengthened beams had the corresponding trend curve with temperature and humidity changes. c) Deflection f versus relative fatigue lifelnn/lnNjmodels of specimens were built in stable hygrothermal environment. Influence factors ofhygrothermal environments were proposed and determined by experiments. Dynamic secantstiffness versus fatigue life equations in cyclic hygrothermal environment and fatigue loadcoupling were built. This laid a good foundation for fatigue life study in hygrothermalenvironment. d) Results of comparisons of S~N curves in different experiment conditions alsoshowed experiment method had a significant impact on mechanical properties of thestrengthened beams and experiment method proposed in this paper is necessary, effective andfeasible.更多还原