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类型 应用研究 预答辩日期 2017-12-04
开始(开题)日期 2013-06-06 论文结束日期 2017-09-29
地点 东南大学九龙湖校区土木交通实验楼N204室 论文选题来源 973、863项目     论文字数 12 (万字)
题目 体外预应力CFRP筋混凝土连续梁疲劳性能研究
主题词 体外预应力连续梁,CFRP筋,疲劳,疲劳内力重分布,寿命预测
摘要 体外预应力混凝土已被广泛应用于桥梁工程、加固工程以及大跨度屋盖等结构工程。随着结构设计使用年限的延长和应用于不利环境(酸、碱、氯盐、潮湿环境等)的情况越来越多,传统钢质的体外预应力筋在交变荷载下的疲劳问题,在腐蚀环境下的锈蚀问题,以及疲劳、锈蚀耦合作用下的锈蚀疲劳问题,一定程度上会对体外预应力结构的安全性和耐久性造成不利影响。碳纤维增强复合材料(Carbon Fiber Reinforced Polymer,简称CFRP)筋因具有轻质高强、耐疲劳、耐腐蚀等优越性能,被认为是能部分替代钢质体外预应力筋的一种理想材料。本文采用试验研究与理论分析相结合的方法,对体外预应力CFRP筋混凝土连续梁的疲劳性能展开了研究,主要研究内容及成果如下: (1)进行了5根截面尺寸及配筋形式完全相同的体外预应力CFRP筋混凝土两跨连续梁的静载及疲劳试验,疲劳试验变量为疲劳荷载水平S(S=Pmax/Pu)。疲劳试验结果表明,试验梁的疲劳破坏均始于梁内普通受拉钢筋的疲劳断裂。试验梁的疲劳寿命随疲劳荷载水平的增加而减小,且疲劳寿命与疲劳荷载水平在双对数坐标系中近似呈线性关系。随着荷载循环次数的增加,试验梁BC跨中挠度、体外CFRP筋应力、钢筋应力及主裂缝宽度不断发展,并呈“快速增长-稳定缓慢增长-急剧增长”的三阶段发展规律。与首次加载时连续梁的弯矩分布相比,BC跨控制截面的弯矩(正弯矩)呈“快速减小-稳定缓慢减小-急剧减小”、中支座截面的弯矩(负弯矩)呈“快速增长-缓慢稳定增长-急剧增长”的三阶段发展规律,连续梁出现了疲劳荷载下由于沿梁纵向各截面刚度不均匀退化而引起的“疲劳内力重分布”现象。疲劳破坏后,BC跨控制截面的疲劳弯矩重分布系数βf超过20%,中支座截面的疲劳弯矩重分布系数βf超过80%。 (2)对体外预应力CFRP筋(钢绞线)混凝土连续梁进行了静力全过程非线性分析,采用MATLAB编程对静载下连续梁的跨中挠度、体外筋应力、普通受拉钢筋应变、控制截面弯矩等参数进行了分析计算。计算结果与试验结果相一致,精度良好。 (3)建立了混凝土、钢筋及CFRP筋的疲劳损伤模型,基于分段线性原理,提出了可以同时考虑疲劳荷载作用下体外预应力CFRP筋混凝土连续梁截面内应力重分布以及沿梁纵向截面间疲劳内力重分布的疲劳损伤全过程非线性分析方法。采用MATLAB编程对疲劳荷载下连续梁的疲劳寿命、跨中挠度、体外CFRP筋应力、普通受拉钢筋应力、控制截面弯矩等重要参数进行了分析计算。与试验实测结果的比较表明,该方法可以较好地描述疲劳荷载作用下体外预应力CFRP筋混凝土连续梁的全过程结构响应,分析模型较为可靠。 (4)基于疲劳全过程非线性分析程序,采用割线刚度法分析了疲劳荷载下体外预应力CFRP筋混凝土连续梁中支座截面次弯矩的变化规律。研究表明,随着荷载循环次数的增加,本文连续梁中支座截面预应力次弯矩呈“快速增长、缓慢增长、迅速增长”的三阶段发展规律。与首次加载时的连续梁中支座截面的预应力次弯矩Ms相比,连续梁在疲劳破坏后的次弯矩Ms增幅可达28%以上。钢筋疲劳断裂后连续梁中支座截面的预应力次弯矩 值以及疲劳荷载引起的次弯矩 增量(与首次加载相比)会随着施加的疲劳荷载水平S的增加而减小,而疲劳荷载下连续梁预应力次弯矩 的增长速率则会随着疲劳荷载水平S的增加而增大。同时指出,疲劳荷载下体外CFRP筋应力的变化对预应力连续梁次弯矩的影响相对较小,而纵向截面间相对刚度的变化对预应力次弯矩的影响占主导作用。 (5)采用编制的疲劳全过程非线性分析程序定量地分析了体外CFRP筋的有效预应力及配筋率、跨中截面与中支座截面受拉钢筋配筋率之比、混凝土强度等级、体外预应力筋类型等参数对体外预应力混凝土连续梁疲劳寿命的影响。通过体外预应力CFRP筋混凝土连续梁与体外预应力钢绞线混凝土连续梁疲劳寿命及破坏形态的比较表明,采用CFRP筋代替钢绞线作为体外预应力筋,不失为提高体外预应力混凝土结构的耐久性和安全性的一种有效方法。 (6)为了便于工程应用,提出了可以不通过疲劳全过程非线性分析即可简便地进行体外预应力CFRP筋混凝土连续梁疲劳寿命分析的“两阶段”疲劳寿命理论预测法。该方法将连续梁疲劳寿命分解为钢筋裂纹形成阶段寿命和钢筋裂纹扩展阶段寿命,并分别采用局部应力-应变法和线弹性断裂力学法进行分析计算。通过与疲劳寿命实测值的比较可见,“两阶段”疲劳寿命理论预测法的预测精度良好。
英文题目 STUDY ON THE FATIGUE BEHAVIOR OF REINFORCED CONCRETE CONTINUOUS BEAMS PRESTRESSED WITH EXTERNAL CFRP TENDONS
英文主题词 externally prestressed continuous beam, CFRP tendon, fatigue, fatigue internal force redistribution, life prediction
英文摘要 Externally prestressed concrete has been widely used in the structural engineering, such as bridge engineering, strengthening engineering, large span roof, etc. With the extension of design life and frequently adverse environment(such as acid, alkali, chloride, moisture) apply on the structures, the fatigue problem under alternating load, the corrosion problem in corrosive environment, and corrosion-fatigue problem of the traditional steel prestressed tendons has seriously affected the safety of the externally prestressed concrete structure, which has become a key constraint in the application of externally prestressed technology. The carbon fiber reinforced polymer (CFRP) tendons are considered to be ideal materials to replace the external steel prestressed tendons, due to many advantages of them such as high specific strength (strength-to-weight ratio), excellent fatigue resistance and non-corrosive characteristics. The present work experimentally and analytically investigated the flexural behavior of reinforced concrete continuous beams prestressed with external CFRP tendons under fatigue loadings. The main contents and results are as follows: (1) Five reinforced concrete continuous beams prestressed with external CFRP tendons were tested under static and fatigue loadings. Each specimen had identical cross-section and reinforcement. Test parameter was the cyclic load level (the ratio between maximum cyclic load and ultimate capacity). The results showed that the fatigue failure of the tested beams began with the fatigue fracture of the internal steel reinforcing bars. With the increase of the cyclic load level, the fatigue lives of the tested beams were reduced rapidly. With the increase of the cycle number, the deflection of BC span was continuously developed, same as the stress of external CFRP tendons and steel reinforcing bars, also the width of the main cracks. Meanwhile all the aforementioned features presented the three-stage development rule which is “rapid growth - slow and steady growth - sharp growth”. Compared with the moment distribution of the continuous beam at the first cyclic, the moment (positive moment) of controlled cross-section in BC span presented the three-stage development rule of “rapid decrease - steady slow decrease - sharp decrease”, while the moment (negative moment) of middle support presented the three-stage development rule of “rapid growth - slow and steady growth - sharp growth”. Continuous beam presented the phenomenon of fatigue internal force redistribution, which was caused by the uneven stiffness degradation of different sections under fatigue loadings. When the fatigue failure occurred, the fatigue moment redistribution coefficient (βf) of the controlled cross-section in BC span was more than 20%, while βf of the middle support was more than 80%. (2) Based on finite element method, an analysis method was developed and implemented into a computer program which can predict the non-linear flexural response of reinforced concrete continuous beams prestressed with external CFRP tendons during the whole process under static loadings. Good agreement was obtained between the measured and the predicted monotonic results. (3) Based on piecewise linear principle and finite element method, a nonlinear analysis method of reinforced concrete continuous beams prestressed with external CFRP tendons during the whole process under fatigue loadings was developed and implemented into a computer program, which can simultaneously consider the coupling of the components and the fatigue internal force redistribution. The comparison between the experimental results and the simulated ones showed that this method can successfully predict the response of reinforced concrete continuous beams prestressed with external CFRP tendons under fatigue loadings. (4) The evolution rule of secondary moment was analyzed in middle support cross-section of reinforced concrete continuous beams prestressed with external CFRP tendons under fatigue and static loadings based on secant stiffness method. The results showed that the secondary moment in middle support cross-section of continuous beams presented the three-stage development rule of “rapid growth - slow growth - sharp growth” with the increase of the cycle number. Compared with the secondary moment (Ms) in middle support cross-section of continuous beams at first cyclic, Ms increased by more than 28% when the fatigue failure occurred. The effect of the stress changes in external CFRP tendons on the secondary moment of continuous beams was relatively small under fatigue loadings, while the effect of the cross-section relative stiffness changes was dominant. This was opposite to the fact that, under static loadings, the effect of the stress changes in external CFRP tendons on the secondary moment was dominant. (5) Quantitative analysis of the main parameters that affect the fatigue life of externally prestressed concrete continuous beams was carried out by using of the fatigue nonlinear analysis program. The results could provide references for design of reinforced concrete continuous beams prestressed with external CFRP tendons under fatigue loadings. The comparison of the fatigue life and failure mode showed that the durability and safety of externally prestressed concrete structures will be effectively improved by using of CFRP tendons instead of steel strands as the externally prestressed tendons. (6) Two-stage fatigue life prediction method which combine of local stress-strain method and linear elastic fracture mechanics theory was developed in order to predict the fatigue life of reinforced concrete continuous beams prestressed with external CFRP tendons. In which, the local stress-strain method was used for predicting the crack initiation life of the steel reinforcing bars, while the linear elastic fracture mechanics theory was used for predicting the crack propagation life of the steel reinforcing bars. Good agreement between the experimental and predicted fatigue life was observed.
学术讨论
主办单位时间地点报告人报告主题
研究生院 2011-10-25 四牌楼校区群贤楼三楼报告厅 朱位秋 非线性随机动力学与控制的哈密顿理论体系及其应用
研究生院 2011-11-3 四牌楼校区群贤楼三楼报告厅 苏先樾 轻质点阵材料的动态力学性能与屈曲分析
结构力学教研组 2013-6-30 四牌楼校区逸夫建筑馆707 宋守坛 FRP混凝土构件研究内容与进展
结构力学教研组 2014-5-16 四牌楼校区逸夫建筑馆707 宋守坛 碳纤维复合材料筋混凝土结构和预应力筋混凝土结构及其应用
结构力学教研组 2012-6-8 四牌楼校区逸夫建筑馆707 程君 The Research Report about CFRP Plate Strengthening Test of Bange Bandu Bridge of Bangladesh
铁道第三勘察设计院集团有限公司 2011-4-15 天津市河北区岷江里10号 程君 京沪高速铁路DK1111+857.43~DK1112+722.96段路基现场试验研究报告
铁道第三勘察设计院集团有限公司 2011-11-3 天津市河北区岷江里10号 程君 京沪高速铁路CFG桩桩帽设计原则和施工方法 研究报告
结构力学教研组 2017-4-11 四牌楼校区逸夫建筑馆707 程君 体外预应力CFRP筋混凝土连续梁疲劳性能研究
     
学术会议
会议名称时间地点本人报告本人报告题目
西南交通大学 2013-10 成都 Calculation Method for Settlement of CFG Pile-Net Composite Foundation in High-Speed Railway
山东大学 2013-5 济南 Research on Stress Distribution of CFG Pile-Net Composite Foundation in High-Speed Railway
中国土木工程学会纤维增强复合材料(FRP)及工程应用专业委员会 2017-7 新加坡 Experimental Study on the Fatigue Behavior of Carbon Fiber Reinforced Polymer Tendons
     
代表作
论文名称
Calculation Method for Settlement of CFG Pile-Net Composite Foundation in High-Speed Railway
Research on Stress Distribution of CFG Pile-Net Composite Foundation in High-Speed Railway
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
梁书亭 正高 教授 博导 东南大学
冯健 正高 教授 博导 东南大学
陈锦祥 正高 教授 博导 东南大学
艾军 正高 教授 硕导 南京航空航天大学
陆伟东 正高 教授 博导 南京工业大学
      
答辩秘书信息
姓名职称工作单位备注
杜二峰 其他 工程师 东南大学