竹集成材单向偏压构件力学性能分析与试验研究

发布时间：2019-01-28 20:07

【摘要】：竹集成材是由原竹经工业化加工而成,在物理性能上优越于传统木材、绿色环保方面优于混凝土、砌体等传统建筑材料的一种具有发展潜力的新型建筑材料。目前,对于竹集成材的研究仍不够成熟,多数研究主要针对材料的基本力学性能和构件轴心受压性能、抗弯性能等,对于竹集成材柱偏心受压性能的研究几乎没有。在实际结构工程中,极少有理想的轴心受压构件,即使是按轴心受压设计的构件,也会因偶然的横向荷载、支座条件不理想或施工制作的偏差等情况而出现附加弯矩。因此,研究竹集成材偏压构件基本力学性能显得十分有意义。本文首先通过试验研究了材料的轴向拉压力学性能,结果表明：竹集成材抗拉强度为119.19 MPa,弹性模量为10.02GPa;抗压强度为51.41MPa,弹性模量为8.71GPa,比例极限为34.43MPa。轴拉破坏为脆性破坏,应力-应变呈线性关系;轴压破坏为塑性破坏,应力-应变初始呈线性关系,随后呈明显的非线性关系。轴压应力-应变曲线可分为两个阶段：小变形弹性阶段和大变形塑形阶段。文章根据此现象采用分段函数对竹集成材单轴向拉压应力-应变关系建立数学模型。受拉和受压的比例阶段均采用直线,受压的塑性段采用二次抛物线,模型与试验曲线吻合良好。其次,参考《木结构试验方法标准》设计了三种不同的长细比竹集成材构件,研究其在不同初始偏心距下的力学性能。分析发现：当初始偏心距一定时,随着长细比的增加,变形增大,承载力降低；当长细比一定时,随着初始偏心距的增加,承载力逐渐减小,变形逐渐增加,二阶弯矩增加。三种不同长细比试件,在偏心荷载作用下,最终都会因为侧向位移很大而出现类似于受弯破坏,且破坏出现于受拉侧。但在整个变形过程中,试件截面始终保持水平,符合平截面假定,而试件的变形曲线与二次多项式函数吻合良好。最后,对竹集成材的偏压承载力作理论分析。根据不同模量理论,推导出竹集成材偏压破坏时挠曲线符合二次多项式函数；结合试验现象,以破坏时拉压边缘是否达到极限应变为破坏准则,提出大偏压和小偏压两种分析模型,并对小偏压下侧向挠度进行修正,求出不同长细比的试件端部的等效轴力和弯矩。通过试验值与理论值对比发现,两者吻合良好。
[Abstract]:Bamboo agglomerated timber is a new type of building material with development potential, which is made from raw bamboo after industrialized processing, and is superior to traditional building materials such as concrete, masonry and so on in terms of physical properties and environmental protection. At present, the research of bamboo timber is still not mature, most of the research mainly focus on the basic mechanical properties of materials, axial compression performance of members, bending performance, and so on, but there is almost no research on eccentric compression performance of bamboo timber columns. In the actual structural engineering, there are few ideal axial compression members, even the members designed according to the axial compression, but also due to accidental lateral load, support conditions are not ideal or the construction of the deviation of the situation such as additional bending moment. Therefore, it is of great significance to study the basic mechanical properties of the composite members. In this paper, the axial tensile and compressive mechanical properties of the bamboos were studied by means of experiments. The results showed that the tensile strength of the bamboos was 119.19 MPa, and the elastic modulus was 10.02 GPA. The compressive strength is 51.41 MPA, the elastic modulus is 8.71 GPA, and the proportional limit is 34.43 MPA. The axial tensile failure is brittle, the stress-strain is linear, the axial compression failure is plastic, the initial stress-strain is linear, and the nonlinear relationship is obvious. The stress-strain curve of axial compression can be divided into two stages: elastic stage of small deformation and plastic stage of large deformation. According to this phenomenon, a mathematical model of uniaxial stress-strain relationship of bamboo agglomerated timber was established by using piecewise function. The proportional stage of tension and compression adopts straight line, and the plastic segment of compression adopts quadratic parabola, and the model agrees well with the test curve. Secondly, according to the Standard of Wood structure Test method, three different kinds of timber components with aspect ratio are designed and their mechanical properties under different initial eccentricity are studied. It is found that when the initial eccentricity is constant, the deformation increases and the bearing capacity decreases with the increase of the slenderness ratio, and with the increase of the initial eccentricity, the bearing capacity decreases gradually, the deformation increases and the second moment increases with the increase of the slenderness ratio. Under eccentric load, three kinds of specimens with different slenderness ratios will eventually be subjected to bending failure due to the large lateral displacement, and the damage will occur on the tension side. However, in the whole deformation process, the section of the specimen is always horizontal, which accords with the assumption of the plane section, and the deformation curve of the specimen is in good agreement with the quadratic polynomial function. Finally, the theoretical analysis of the eccentric bearing capacity of bamboo timber is made. According to the theory of different moduli, the deflection curve of bamboo lumber subjected to biasing failure accords with quadratic polynomial function. According to the experimental phenomenon, two kinds of analytical models, large bias and small bias, are put forward, and the lateral deflection under small bias is corrected by taking the limit strain of tension and compression edge as failure criterion. The equivalent axial force and bending moment at the end of the specimen with different slenderness ratio are obtained. By comparing the experimental values with the theoretical values, it is found that the two are in good agreement with each other.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU531.3

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