【作者】 徐新生；

【导师】 王铁成；

【作者基本信息】 天津大学 ， 结构工程， 2007， 博士

【摘要】 钢筋锈蚀是结构丧失承载力,影响预期使用寿命的主要因素,也是影响钢筋混凝土结构耐久性的一个重要问题。碳素、芳纶、玻璃等高性能连续纤维具有耐腐蚀、重量轻、强度高、抗电磁辐射、抗疲劳等一系列优良特性,采用拉挤工艺制成的FRP筋(Fiber Reinforced Plastics)可以替代或部分替代钢筋用于混凝土结构工程中,具有很高的开发价值。但是,FRP筋是弹性体,到达抗拉极限强度时突然断裂,用于普通混凝土梁时,没有屈服点和塑性阶段,会发生脆性破坏。因此,研究FRP筋力学性能及其混凝土梁抗弯性能,分析FRP筋混凝土梁在荷载作用下的弯曲性能和破坏机理,对结构设计具有重要的意义。本文研究了FRP筋的成型方法、锚固方法,研制开发了新的FRP筋;进行了FRP筋基本力学性能和FRP筋混凝土梁抗弯性能试验分析,对FRP筋混凝土受弯构件的受力变形全过程进行了有限元分析,结果表明:1.与钢筋相比,FRP筋抗拉强度高(本文CFRP筋抗拉强度为1779MPa,GFRP筋为993MPa),弹性模量低,延伸率小;单一纤维FRP筋拉伸破坏为断裂破坏,应力-应变关系破坏前基本呈直线关系,无明显的塑性阶段;提出了应力-应变本构模型及设计指标。2.两种抗拉强度、延伸率和极限应变均不相同的纤维混杂形成的HFRP筋,只要低延伸率纤维的体积数低于其临界体积数,二者混杂后的应力-应变关系就会出现类似于钢材的“屈服平台”;给出了HFRP筋临界体积数、抗拉强度、弹性模量设计公式。3.研究了FRP筋混凝土梁变形特征和破坏机理,截面应变基本符合平截面变化;初始裂缝宽度大,开展位置高,裂缝发展较快,分布均匀;挠度变化大,荷载-挠度曲线近似双直线变化;FRP筋的抗拉刚度(弹性模量×截面积)和梁的截面高度对挠度影响较大,混凝土强度和荷载类型的影响较小。4. FRP筋混凝土梁破坏分为两种破坏模式,基于平截面假定,提出了两种破坏模式下FRP筋混凝土梁正截面承载力计算公式;以双直线的弯矩-曲率关系模型为基础提出了挠度计算公式,与试验结果吻合较好。提出的FRP筋混凝土梁的设计方法可作为FRP筋混凝土梁的设计参考。更多还原

【Abstract】 The erosion of steel bars, which can result in the failure of bearing capacity of the RC structures, has also been considered to be a chief factor to affect the life span and the durability as well. Therefore, high-performance fibers including carbon and glass, with light weight, high strength, resistance to erosion, fatigue or electro-magnetic radiation, which can be made into FRP bars with special technique, can replace steel bars in concrete structures. However, as a type of elastic material, its sudden rupture without any yielding point or plastic property in the ultimate stage of tension will cause the unexpected failure of flexural members. It is of great importance to study mechanical property of FRP bars as well as the flexural property and failure mechanism of FRP-reinforced concrete beams.In this paper, the manufacturing and anchorage of the FRP bars are studied, and a new type of FRP bar is reserched and developed. Experiments are conducted to study the mechanical property of FRP bars and the flexural property of FRP-reinforced concrete beams. We also make FEM analysis of the whole process of the deformation of the beams. It is indicated that:1. In contrast to steel bars, FRP bars have higher tensile strength(the tensile strength of CFRP is 1779Mpa and GFRP is 993Mpa) along with lower elastic modulus and lower extension rate. The failure of single FRP bar is a kind of rupture failure with a basic linear stress-strain relationship, lacking evident plastic stage. The experimental method, stress-strain model and parameters for design have been proposed.2. For hybrid FRP(HFRP) bars, with two groups of fibers of different tensile strength, extension rate and ultimate strain, as long as the low elongation fibers doesn’t exceed the boundary content, the stress-strain relationship of the HFRP bars will have a yielding stage similar to steel bars. The formula has been offered to design the boundary content, tensile strength and elastic modulus of HFRP bar.3. The deformation characteristics and failure mechanism have been studied. Strain along the cross section is proportional to the height, which we call a“plane section”. With wide original cracks and fast development, the cracks have an even distribution. The deflection varies greatly, while the load-deflection curve looks like double lines. Tensile rigidity(elastic modulus multiple area of cross section) of FRP and height of the beams seem to affect the deflection in a greater extent than concrete strength and type of loads.4. Based on the“plane section”theory, the flexural bearing capacity formulas for the two types of failure modes have been produced. The deflection formula on the basis of double-line model of M-￠curve is applied to obtain desirable agreement between calculated results and experimental data. The proposed design method can serve as a reference for those designers who are going to deal with FRP-reinforced concrete beams.更多还原