【作者】 李建辉；

【导师】 邓宗才；

【作者基本信息】 北京工业大学 ， 结构工程， 2010， 博士

【摘要】 腐蚀问题是目前混凝土结构领域面临的世界性难题之一,而FRP(Fiber Reinforced Polymer)复合材料由于具有耐腐蚀、轻质、高强、施工方便等突出优点,在腐蚀结构抗震加固领域具有广阔的应用前景,但单一FRP变形能力不足制约了其发展,混杂技术是解决以上问题的有效途径。因此,选取具有良好延性的混杂FRP(Hybrid FRP, HFRP)对腐蚀混凝土柱进行抗震加固具有重要的工程实际和理论意义。本文从试验、理论和设计方法三方面较系统地研究了HFRP及其加固腐蚀混凝土柱的抗震性能,主要研究内容包括:(1)为了制备优异综合性能的HFRP复合材料,首次提出了碳纤维(Carbon FRP, CFRP)/芳纶纤维(Aramid FRP, AFRP)/玻璃纤维(Glass FRP, GFRP)三种纤维混杂思路。完成了11个不同纤维种类、碳纤维相对体积含量、铺层方式的HFRP复合材料试件的单轴拉伸试验,并通过11根混凝土梁抗弯试验进一步验证HFRP加固混凝土结构的效果。在材料研究的基础上,建立了简单、实用的HFRP复合材料强度模型。研究表明:CFRP/AFRP/GFRP混杂FRP复合材料具有良好的混杂效应和加固效果,混杂效应系数可达0.647。(2)由于建立HFRP约束混凝土应力-应变曲线模型是进行结构抗震加固设计及其加固效果评价的前提,本文在试验和已有成果的基础上,建立了新的HFRP约束混凝土应力-应变曲线模型,该模型使用轴向、横向和体积应变来衡量约束混凝土的内部损伤,以体现HFRP变约束力对被约束混凝土微观损伤的影响,从而使模型简化且具有明确的物理含义;同时,该模型采用了更能真实体现约束效应的割线模量,并且引入依赖于混凝土本身特性的割线模量软化系数进行计算。(3)正确评估FRP加固腐蚀钢筋-混凝土粘结性能是评价FRP加固腐蚀结构效果的首要问题,本文通过96个试件的拉拔试验,研究了不同钢筋种类、不同保护层厚度、不同腐蚀率、不同FRP约束下腐蚀钢筋-混凝土粘结性能,并建立了简单的腐蚀钢筋粘结-滑移模型。结果表明:当钢筋腐蚀率小于5%时,影响试件峰值粘结强度的主要影响因素是钢筋种类、混凝土保护层厚度;FRP约束对试件峰值粘结强度影响较小,但对减缓粘结应力下降速度,维持粘结应力较为有效。(4)完成了10根CFRP/AFRP/GFRP层间混杂FRP布加固腐蚀混凝土柱在低周反复荷载下的抗震性能试验,分析了各柱强度、刚度、变形、累积耗能以及损伤的发展规律,探讨了钢筋腐蚀、轴压比、配箍率等因素对柱整体抗震特性的影响,揭示了HFRP加固腐蚀混凝土柱在反复荷载作用下的失效机制。结果表明:CFRP/AFRP/GFRP层间混杂FRP布可以显著改善腐蚀柱的抗震性能,累积耗能最大可提高12.5倍。(5)根据CFRP/AFRP/GFRP层间混杂FRP布加固腐蚀混凝土柱抗震性能试验结果,在完好钢筋混凝土构件截面分析和Clough滞回规则的基础上,建立了HFRP加固腐蚀混凝土柱恢复力模型,该模型率先引入钢筋粘结-滑移模型来考虑腐蚀对钢筋-混凝土粘结界面的影响。并且提出了HFRP加固腐蚀混凝土柱基于位移性能的抗震设计方法,该方法简单、适用,且精度较好。这将为HFRP加固腐蚀混凝土柱抗震性能评估和设计提供指导作用。本文的主要创新点如下:(1)建立了新的HFRP约束混凝土应力-应变曲线模型。该模型使用轴向、横向和体积应变来衡量约束混凝土的内部损伤,以体现HFRP变约束力对约束混凝土内部损伤的影响,从而使模型简化且具有明确的物理含义。同时,采用了更能真实体现变约束效应的割线模量。(2)完成了10根HFRP加固腐蚀混凝土柱在低周反复荷载下的抗震性能试验研究。首次提出了碳/芳纶/玻璃三种纤维混杂思路,该混杂布具有较高延性。分析了各腐蚀混凝土柱在低周反复荷载作用下的强度、刚度、变形、累积耗能以及损伤的发展规律。同时,试验研究了FRP加固腐蚀钢筋-混凝土粘结性能,为理论分析提供了试验数据。(3)提出了HFRP加固腐蚀混凝土柱恢复力模型及抗震设计方法。在完好钢筋混凝土构件截面分析和Clough滞回规则的基础上,建立了HFRP加固腐蚀混凝土柱恢复力模型,该模型率先引入钢筋粘结-滑移模型来考虑腐蚀对钢筋-混凝土粘结界面的影响。并且提出了HFRP加固腐蚀混凝土柱基于位移性能的抗震设计方法。总之,本文所研究的CFRP/AFRP/GFRP混杂FRP布抗震加固新方法能显著改善腐蚀混凝土柱的抗震性能,其施工工艺简便,在腐蚀结构抗震加固领域具有广泛的应用前景。更多还原

【Abstract】 Reinforcement corrosion is one of the major worldwide deterioration problems for RC structures, and Fiber reinforced polymers (FRPs) are becoming popular for seismic strengthening of corroded RC structures, due to their corrosion resistance, high strength-to-weight ratios, ease of installation and so on, but the deformation capacity of single FRP composites is insufficient, which restrict severely FRP composites to further using widely in field. However, hybrid technique is an effective method for solving this problem. Therefore, the research on seismic strengthening of corroded RC columns with hybrid FRP (HFRP) composites with excellent comprehensive properties has important engineering and theoretical value. This paper researches systematically on hybrid FRP composites and seismic performance for strengthening corroded RC columns in three aspects including experiments, theory and design method, main contents are listed as follow:(1) In order to make up the HFRP composites with excellent comprehensive properties, a hybrid idea of Carbon FRP (CFRP), aramid FRP (AFRP) and Glass FRP (GFRP) is firstly proposed. this paper researches experimentally uniaxial tensile property of eleven HFRP composites specimens, hybrid parameters are fiber species, relative volume percent of carbon fiber, laminated mode, and the effects of HFRP composites on strengthening RC structures are verified in further by flexural experiments of eleven RC beams. Based on the experimental study of material properties, a simple and practical strength model for HFRP composites is established. The results show the CFRP/AFRP/GFRP hybrid FRP composites have good hybrid effect and strengthening effect for RC structures, the hybrid effect coefficient is 0.647.(2) Because the stress-strain model of concrete confined by HFRP composites is the premise of seismic strengthening design and strengthening effect evaluation for concrete structures strengthened with HFRP composites, based on the experimental data and the analysis on the research production, a stress-strain model is developed for concrete confined with HFRP composites. The feature of the model is that it includes the effects of HFRP confinement on the concrete microstructure by evaluating the internal concrete damage using the axial, lateral and volumetric strains, which introduces that the model is simple and has a physical and fundamental interpretation with the mechanical behavior of concrete. Meantime, the secant concrete modulus is used in the model and expressed as a function of the secant modulus softening coefficient.(3) Proper evaluation of the bond characteristics of corroded reinforcement in FRP-wrapped concrete is prime importance in FRP repair of corrosion-damaged RC members. Pull-out tests of 96 specimens with different reinforcement types, cover depths, corrosion degrees, with or without strengthening using FRP are carried out to study the bond behavior between corroded reinforcement and concrete. Meantime, a simple bond-slip model for corroded reinforcement is proposed. The results show that when the corrosion degree is below 5%, the main influencing factors for the peak bond strength are reinforcement type and cover depth, FRP confinement plays a less important role, but FRP confinement can effectively slow down the declining speed of bond stress.(4) The seismic experiments of ten corroded RC columns strengthened with CFRP/AFRP/GFRP laminated hybrid FRP sheets under low frequency cyclic loading are carried out, bearing capacity, stiffness, ductility, energy dissipation and damage evolution are analyzed, the effects of the reinforcement corrosion, axial compression ratio and stirrup reinforcement ratio on the seismic behavior are discussed, and the failure mechanism of corroded RC columns strengthened with HFRP composites under low frequency cyclic loading is revealed. Results show that the CFRP/AFRP/GFRP laminated hybrid FRP sheets can improve significantly the seismic performance of corroded RC columns, the accumulated energy dissipation can be increased by 12.5 times.(5) According to the experimental results of corroded RC columns strengthened with CFRP/AFRP/GFRP laminated hybrid FRP sheets, the restoring force model of RC corroded columns strengthened with HFRP composites is presented based on cross-section analysis for undamaged RC element and Clough hysteresis rule, the bond-slip model is firstly introduced to consider the effect of corrosion on bond characteristic in the model. And displacement-based seismic design method of corroded RC columns strengthened with HFRP composites is presented, this method is simple, practical and accurate, which will play a guiding role in seismic evaluation and design of corroded RC columns strengthened with HFRP composites.The main originalities of this paper lie in:(1) Stress-strain model of concrete confined by HFRP composites is developed. The model includes the effects of HFRP confinement on the concrete microstructure by evaluating the internal concrete damage using the axial, lateral and volumetric strains, which introduces that the model is simple and has a physical and fundamental interpretation with the mechanical behavior of concrete. Meantime, the secant concrete modulus is used in the model.(2) The seismic experiments of ten corroded RC columns strengthened with hybrid FRP sheets under low frequency cyclic loading are systematically carried out. The seismic performance of corroded RC columns strengthened with hybrid fiber sheets of CFRP, AFRP and GFRP is firstly researched, the hybrid fiber sheet has good ductility. Bearing capacity, stiffness, ductility, energy dissipation and damage evolution of ten corroded RC columns strengthened with hybrid FRP sheets under low frequency cyclic loading are analyzed. Meantime, the bond characteristic of corroded reinforcement in FRP-wrapped concrete is researched by pull-out tests, which provides experimental data for theoretical analysis.(3) Restoring force model and seismic design method of RC corroded columns strengthened with HFRP composites are presented. Based on cross-section analysis for undamaged RC element and Clough hysteresis rule, the restoring force model of RC corroded columns strengthened with HFRP composites is presented, the bond-slip model is firstly introduced to consider the effect of corrosion on bond characteristic in the model. And displacement-based seismic design method of corroded RC columns strengthened with HFRP composites is developed.In conclusion, the seismic strengthening technique of using CFRP/AFRP/GFRP laminated hybrid FRP sheets for corroded RC columns is developed, and the seismic performance of corroded RC columns can be improved significantly. The construction technology is simple and convenience, so that it has a wide application prospect in seismic strengthening field.更多还原