大跨度预应力CFRP筋索FRCC受弯构件受力性能研究

发布时间：2018-01-01 09:32

本文关键词：大跨度预应力CFRP筋索FRCC受弯构件受力性能研究　出处：《东南大学》2016年硕士论文　论文类型：学位论文

【摘要】：碳纤维增强复合材料筋CFRP (Carbon Fiber Reinforced Polymer)筋和纤维增强水泥基复合材料FRCC (Fiber Reinforced Cement Composite)是土木工程领域的两种新型高强建筑材料。与普通钢筋混凝土结构相比,CFRP筋具有轻质高强、耐腐蚀、抗疲劳等良好的物理性能,使其能够代替传统的预应力钢筋作为体外预应力筋的材料,这已成为研究热点之一。但由于FRP材料和普通的混凝土材料的脆性破坏性能,采用FRP配筋的混凝土结构的延性一般较差,而引入适量钢纤维的FRCC材料由于其强度高、极限压应变大等特点,能够较好的克服体外预应力CFRP筋混凝土结构这一所固有的缺陷。而且由于该种材料较高的抗拉性能,在提高结构的抗裂度方面能够发挥较大作用。采用这两种新型材料组合而成的体外预应力混凝土结构,对于克服钢筋的锈蚀实现混凝土结构的耐久性以及减轻结构自重具有重要的工程价值,为结构往大跨度方向发展提供了可能。本文主要采用了不同直径的国产光圆CFRP筋和纤维增强水泥基复合材料,针对跨高比为20的体外预应力CFRP筋索FRCC受弯构件的抗弯性能进行了相应的试验研究,包括材料性能研究和构件力学性能研究。主要研究内容包括：(1)采用本课题组自主研发的夹片式锚具进行了直径8mm和直径11mm的两种国产光圆CFRP筋的锚具静载锚固性能试验研究,主要包括CFRP筋的抗拉强度、弹性模量和延伸率的测量,获得CFRP筋的应力-应变关系曲线。试验表明,本文中的CFRP筋锚具组装件基本能发挥出CFRP筋的极限抗拉强度,没有出现滑移现象,具有一定的工程实用价值。(2)通过棱柱体和8字模试验研究了纤维增强水泥基复合材料FRCC的材料性能,主要参数包括抗拉强度、抗压强度、弹性模量、极限压应变和极限拉应变等,并获得了相应的抗拉和抗压性能的应力—应变全曲线,基于试验结果建立了相应的FRCC单轴受压和受拉的本构关系。(3)完成了1根体外预应力CFRP筋普通混凝土梁和5根体外预应力CFRP筋FRCC梁的抗弯性能试验研究。研究的参数主要有：混凝土类型、CFRP筋直径和张拉控制力。根据相应的试验结果和试验现象分析了构件的破坏模式,详细讨论了构件的受力过程、挠度变化、预应力筋的应力增量等。同时针对不同的参数将相应的构件的试验结果进行了对比,分析了其试验结果产生差异的原因。试验结果表明：相同配筋率和预应力度条件下的FRCC梁的极限承载力均要比普通混凝土梁的承载力要高50%左右,且具有更加良好的极限变形能力和延性水平,其延性水平提高35%左右。另外,在正常使用阶段,试验梁的裂缝分布形态及其发展路径表明：FRCC梁与普通混凝土梁相比,其裂缝分布呈现出“细而密”的特点,这主要与FRCC的材料特性有关,其含有的钢纤维能够抑制裂缝的扩展,同时提供混凝土开裂时的桥接应力,使得材料塑性发展更为充分,裂缝发展分布比较均匀。(4)在试验研究的基础上对体外预应力CFRP筋混凝土构件的受力机理进行了理论计算分析。首先从既有的体外预应力筋的应力增量的计算方法揭示了其受力机理,包括粘结折减系数法、基于塑性铰理论的计算方法、基于截面配筋综合指标的方法等。然后根据Pannel模型并结合本试验的实测数据推导了FRCC构件截面(不包括体外预应力筋)塑性铰长度与截面受压区高度之间的计算公式Lp=15.1c。采用基于挠度变形的应力增量的计算方法的修正简化计算公式对试验构件进行了相应的计算,并与试验结果进行了相应的对比,吻合良好。(5)关于体外预应力CFRP筋FRCC构件的截面开裂弯矩的计算,参考RPC材料的关于其截面塑性发展系数的研究成果,对试验构件进行了相应的计算,与试验的结果相比,表明塑性发展系数取为1.65时具有较好的符合程度。而对于正常使用阶段的体外预应力CFRP筋FRCC构件进行了刚度分析和最大裂缝宽度的计算。刚度分析时考虑了截面受拉区的拉应力的贡献。进行最大裂缝宽度的计算时,分别根据基于塑性铰长度的原理和基于有粘结预应力构件原理引入体外筋面积的折减系数来计算构件的最大裂缝宽度。然后通过考虑FRCC材料中受拉区钢纤维对截面裂缝开展的有利影响,引入钢纤维所产生的受拉区影响系数和峰值压应变的影响系数,提出了体外预应力CFRP筋FRCC梁的最大裂缝宽度的修正计算公式,对试验构件进行了计算,与试验结果符合较好。(6)体外预应力CFRP筋]FRCC梁良好的极限变形能力是其相比于体外预应力普通混凝土梁的一个较为明显的优势。由于CFRP筋是一种线性材料,没有明显的屈服点,采用传统的极限位移与屈服位移比值的做法来分析延性并不完全合适。因此本文根据Naaman和Jeong提出的采用能量的观点定义延性指标来揭示其本质,并通过加权平均思想来确定卸载曲线刚度理论值,然后将基于能量观点求得的延性指标的理论值与试验值进行对比,确定其体外预应力CFRP筋FRCC构件的延性水平。(7)本文还采用了有限元软件Opensees进行了建模分析,通过将试验梁的模拟值与试验值进行对比以验证模型的合理性。然后对影响构件力学性能的不同参数做具体分析,主要包括对构件的极限承载力、挠度、体外预应力筋的应力增量等力学指标做具体分析,以分析不同参数下构件受力性能的变化趋势。综合试验结果与理论计算分析表明：体外预应力CFRP筋FRCC受弯构件与体外预应力普通混凝土构件相比,在相同配筋率和预应力度下,FRCC构件具有较高的极限承载力、优异的裂缝分布形态和较高的延性水平。良好的极限变形能力和较高承载能力为结构向大跨高耸方向发展提供了可能,而正常使用阶段优异的裂缝分布发展对结构的耐久性、长周期性能具有较为有利的控制作用。
[Abstract]:Carbon fiber reinforced composite reinforced CFRP (Carbon Fiber Reinforced Polymer) and steel fiber reinforced cement based composites FRCC (Fiber Reinforced Cement Composite) in the field of civil engineering two high-strength building materials. Compared with ordinary reinforced concrete structure, CFRP reinforcement is lightweight, corrosion resistance, fatigue resistance and good physical properties. It can replace the traditional prestressed external tendons as material, it has become a research hotspot. But due to the destruction of the properties of FRP materials and ordinary concrete brittleness, concrete structure with FRP reinforcement ductility is generally poor, and the introduction of appropriate amount of steel fiber FRCC material due to its high strength, ultimate pressure strain and other characteristics, can overcome the inherent defects of the external prestressed CFRP reinforced concrete structure better. And because of the high tensile material Can, can play a larger role in improving crack resistance structure. External prestressed concrete structure using the two kinds of new material combinations, to overcome the corrosion of steel for durability of concrete structure and reduce the weight of structure has important engineering value, provides the possibility for large span structure to the direction of development. This paper mainly uses the the domestic light round CFRP bar and different diameter of fiber reinforced cement base composite materials, the flexural performance of span to depth ratio of external prestressing CFRP tendons 20 cable FRCC flexural members with the corresponding experimental research, including research material properties and mechanical properties. The main research contents include: (1) by using the sandwich type the research group of anchorage independent research and development of two kinds of domestic light round CFRP bar diameter 8mm and 11mm diameter anchorage experimental study on anchorage performance of static load, including CFRP bars The tensile strength, elastic modulus and elongation measurement, obtain the curve of CFRP bars stress-strain relationship. The results show that the CFRP anchor in this assembly can reach the ultimate tensile strength of CFRP bars, no slip phenomenon, has a certain practical value. (2) through the prism and 8 experimental study on the matrix properties of FRCC fiber reinforced cement based composite materials, the main parameters include tensile strength, compressive strength, elastic modulus, ultimate strain and ultimate tensile strain, and obtained the corresponding tensile and compressive properties of the stress-strain curves of the test results, the establishment of the corresponding FRCC uniaxial compression and the constitutive relation of tension (3). Based on the experimental research on the flexural performance of 1 externally prestressed with CFRP tendons concrete beams and 5 prestressed CFRP reinforced FRCC beam has been completed. The experimental parameters include: type of concrete, reinforced with CFRP The diameter and tension control force. According to the test results and the corresponding experimental phenomena analysis of failure modes of structure, stress process, components are discussed in detail the deflection, the stress increment of prestressed tendons. At the same time according to different parameters will test the corresponding component results were compared, analysis of the test results the reason for the difference. The experimental results show that the same ratio of reinforcement and prestressed FRCC beam intensity limit under the condition of bearing capacity are 50% higher than the bearing capacity of reinforced concrete beams, and has better ultimate deformation capacity and ductility level, the ductility level increased by about 35%. In addition, in normal use that stage, the test beam crack distribution and its development path: compared with ordinary concrete beam FRCC beam, the crack distribution shows the characteristics of "small and dense", which is mainly related to the material properties of FRCC, including the Some expansion of steel fiber can restrain the crack bridging, while providing concrete cracking when the stress of the material plastic development more fully, crack distribution. (4) on the basis of experimental research on prestressed CFRP reinforced concrete member force mechanism for the theoretical analysis. Firstly, from the existing calculation method of stress increment of external prestressed tendons reveals the stress mechanism, including the bond discount coefficient method, calculation method of plastic hinge theory based on reinforcement of the comprehensive index method based on Pannel model. Then according to the actual data and the test is derived for the FRCC section (not including in vitro tendons) between the plastic hinge length and depth of compression zone calculation formula of the deflection deformation should be corrected by Lp=15.1c. calculation method of stress increment formula of test structure based on The corresponding calculation, and experimental results are in good agreement with the corresponding contrast. (5) calculation of cracking moment about external prestressing CFRP tendons FRCC components, on the cross-section plastic development coefficient based on research results of RPC materials, the test components were calculated and compared with the test the results show that, consistent with the degree with the plastic development coefficient is 1.65. And the FRCC component of external prestressing CFRP tendons were calculated using normal phase stiffness analysis and maximum crack width. The stiffness analysis considering the sectional tension zone of tensile stress with the maximum crack width was calculated. When respectively according to the principle of plastic hinge length based on a maximum crack width to calculate prestressed component principle introduced in vitro reinforcement area reduction factor. Then by considering the material by FRCC The beneficial effect of steel fiber on the tensile zone of crack section, introduction of the steel fiber produced by the tension effect coefficient of compressive strain coefficient and peak value, put forward the modified calculation formula of maximum crack width of FRCC beams with external CFRP tendons, the test specimens were calculated. Good agreement with the testing results (6) limit]FRCC external CFRP tendons good beam deformation is one of the more obvious advantages compared with the ordinary prestressed concrete beams. The CFRP bar is a kind of linear material, no obvious yield point, using the traditional limit displacement and yield displacement ratio approach to ductility analysis is not entirely appropriate in this paper. According to Naaman and Jeong proposed the definition of ductility index of the point of view of energy to reveal its essence, and through the idea of weighted average to determine the unloading stiffness curve theory value, and then based on energy The view of ductility index the theoretical values were compared with the experimental values, determine its ductility level of external prestressing CFRP tendons FRCC component. (7) this paper uses the finite element software Opensees modeling analysis, were compared to verify the rationality of the model and test the simulation value through the test beam. Then the different parameter values the influence of mechanical properties in detail, including the bearing capacity limit of deflection of the beam, the stress increment of the mechanical index makes a concrete analysis of external prestressed tendons, to analyze the changing trend of the force performance of the component under different parameters. By the comprehensive test results and theoretical analysis show that: FRCC external CFRP tendons bending with prestressed reinforced concrete members should be compared in the same intensity ratio of reinforcement and pre, ultimate bearing capacity of FRCC component is high, morphology and high crack distribution excellent Good ductility level, good limit deformation capacity and high carrying capacity provide the possibility for the structure to develop in a long span and high direction, while the excellent crack distribution in normal operation stage has a favorable control effect on the durability and long term performance of the structure.

【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU398.9

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