不同配筋率下CFRP加固再生混凝土梁抗弯性能研究

发布时间：2018-05-29 03:04

本文选题：再生混凝土 + 碳纤维布　；参考：《西华大学》2016年硕士论文

【摘要】：目前我国混凝土的用量不断增长,在崇尚保护环境和科学发展的今天,过量开采天然骨料用于制备混凝土,将对环境造成不可弥补的破坏,因此对再生混凝土的研究应用有着重要意义。由于再生混凝土的来源和制备工艺比较特殊,因此使其具有孔隙率、吸水率等较大,而强度、弹性模量等较低,抗渗性、抗冻性、收缩、徐变等较差的特点,制约了再生混凝土的发展。本文将6根不同再生骨料取代率、不同受力主筋直径的混凝土梁分成两组,每组试验梁受力主筋直径相同,并包含1根普通混凝土梁、1根再生混凝土梁、1根CFRP布加固后的再生混凝土梁,研究其抗弯性能。并进一步采用软件进行数值模拟分析。其中主要研究工作和成果如下:1、对CFRP布材料性能和加固方法进行研究,讨论了混凝土、钢筋、CFRP布本构方程,并进行CFRP布加固再生混凝土正截面破坏试验,考察CFRP布对再生混凝土梁的承载力、挠度、裂缝开展等内容的影响程度。经过碳纤维布加固后的试验梁,其抗弯承载力得到提高,并且延缓裂缝的出现。裂缝发展速度较缓慢,在极限荷载的25%~85%左右剪弯段斜裂缝发展迅速。2、CFRP布可以有效抑制混凝土梁表面的裂缝出现与开展,加固后的再生混凝土梁开裂后挠度以较慢的速度增长。随着主筋直径的增大,CFRP布与钢筋共同承担梁底部拉应力的效果更好,CFRP布的利用率有所提高,梁体刚度损失减小。梁开裂后,弯矩产生的拉应力大部分由CFRP布来抵抗,受主筋直径的影响较小。3、利用有限元分析理论,针对试验数据建立有限元数值分析模型,讨论模拟再生混凝土梁所用的有限元单元类型和破坏准则,得到与试验结果较吻合的数值模型。对数值模拟结果与试验结果比对,验证数值分析结果的准确性,分别研究钢筋、碳纤维布应力应变云图,得到CFRP布加固再生混凝土梁各材料的整体受力状态。(1)在极限荷载的60%左右,钢筋的应变达到极限应变,此时钢筋屈服,此后拉应力将全部由CFRP布承担。(2)碳纤维布加固后的试验梁,受拉钢筋的应变滞后于碳纤维布应变,随着配筋率的增加,滞后程度减弱。碳纤维布在较大配筋率下更能发挥其抗拉性能,减小梁体刚度损失。(3)混凝土开裂时刻的第一主应力最大值发生在加载点对齐位置附近,混凝土梁破坏时刻的第一主应力最大值发生在梁剪弯段中间位置。因此混凝土开裂过程表现为跨中裂痕首先发展,当加载到极限荷载的1/4时,弯剪段裂痕迅速发展,最终因CFRP布断裂而发生弯曲破坏。4、对有限元模型的纵向受力钢筋的参数进行更改,得出不同配筋率的极限承载力。根据CFRP加固混凝土结构受弯承载力计算公式对CFRP加固再生混凝土受压区高度按公式进行修正。
[Abstract]:At present, the amount of concrete is increasing in our country. In today's advocation of environmental protection and scientific development, excessive exploitation of natural aggregate for concrete preparation will cause irreparable damage to the environment. Therefore, it is of great significance to the research and application of recycled concrete. The source and preparation process of recycled concrete are very special, so the production of recycled concrete is very special. It has the characteristics of low porosity, water absorption, low strength, modulus of elasticity, impermeability, frost resistance, shrinkage, creep and other poor characteristics, which restrict the development of recycled concrete. In this paper, 6 concrete beams with different recycled aggregate replacement rates and different strength main tendons are divided into two groups. Each test beam is subjected to the same diameter of the main reinforcement. With 1 ordinary concrete beams, 1 recycled concrete beams and 1 regenerated concrete beams strengthened with CFRP cloth, the flexural performance of the reinforced concrete beams is studied. The software is used to carry out numerical simulation analysis. The main research work and results are as follows: 1, the properties and reinforcement methods of CFRP materials are studied, and the constitutive equation of concrete, steel and CFRP is discussed. The influence degree of CFRP cloth on the bearing capacity, deflection and crack development of recycled concrete beams was investigated by CFRP reinforced concrete reinforced recycled concrete cross section failure test. The bending bearing capacity of the reinforced concrete beams strengthened by CFRP was improved, and the crack development was delayed. The crack development speed was slow, 25% of the limit load. The slanting cracks in the left and right shear and bending sections develop rapidly in.2, and CFRP cloth can effectively restrain the appearance and development of cracks on the surface of concrete beams. After the reinforcement of the reinforced concrete beams, the deflection of the reinforced concrete beams increases at a slower speed. With the increase of the diameter of the main reinforcement, the effect of the tensile stress at the bottom of the beam is better and the utilization ratio of the CFRP cloth is raised with the increase of the diameter of the main reinforcement. After the beam cracking, the tensile stress produced by the bending moment is mostly resisted by the CFRP cloth, and the influence of the diameter of the main tendons is less.3. The finite element numerical analysis model is set up by the finite element analysis theory, and the finite element model and failure criterion used in the simulated regenerated concrete beam are discussed, and the test is obtained and tested. The numerical simulation results are compared with the experimental results, and the accuracy of the numerical analysis results is verified. The stress and strain nephogram of the reinforced steel and carbon fiber cloth is studied, and the overall stress state of the materials of the regenerated concrete beams strengthened by CFRP cloth is obtained. (1) the strain of the steel bar reaches the limit strain at the limit load of about 60%. When the reinforcing bar yields, the tensile stress will be all made by the CFRP cloth. (2) the strain of the tensile steel is lagged behind the strain of carbon fiber cloth after the reinforcement of carbon fiber cloth. With the increase of the reinforcement ratio, the lag degree weakens. The stiffness loss of the beam is reduced by the larger reinforcement ratio. (3) the cracking time of the concrete is reduced. The maximum value of the first principal stress occurs near the alignment position of the loading point. The maximum value of the first principal stress of the concrete beam at the moment of failure occurs at the middle position of the beam shear bending section. Therefore, the cracking process of the concrete is first developed in the middle span crack. When the load to the limit load of 1/4, the cracks in the shear section rapidly develop and finally break with the CFRP cloth. The bending failure.4 is taken, the parameters of the longitudinal reinforced bar in the finite element model are changed, and the ultimate bearing capacity of the different reinforcement ratio is obtained. According to the formula of the flexural bearing capacity of the reinforced concrete structure reinforced by CFRP, the height of the compression zone of the regenerated concrete reinforced by CFRP is amended according to the formula.
【学位授予单位】：西华大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU37

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