摘 要

本文首先概述已有几个木材应力-应变关系模型及其数学表达式，并着重介绍重组竹的本构关系。从加载到破坏，受拉应力-应变始终符合胡克定律，呈线性关系；受压时，在比例极限内材料的应力-应变关系为线性；一旦超过比例极限，材料受压将进入塑性阶段，在达到极限抗拉强度之前为塑性强化阶段，此后压应力开始减小，进入塑性软化阶段，直到构件破坏。本文中用两个系数不同的二次函数分别表示塑性强化阶段和明确材料的本构关系对梁-柱构件的弹塑性分析有非常重要的作用，是理论推导分析的基础。

论文对欧拉-伯努利梁理论、铁木辛柯梁理论和梁-柱理论作了简要介绍，并在此基础上，以重组竹梁四点弯曲试验为例，对构件受弯破坏进行弹塑性分析。考虑塑性阶段受压区材料的软化，重新推导破坏截面应力分布均匀性系数公式，并给出构件极限承载力和变形公式，将理论计算值与试验结果进行比较，验证根据定义的均匀性系数计算出的结果具有准确性和可行性。

关键词：类木复合材料；本构关系；梁-柱理论；四点弯曲；应力分布均匀性系数；

Uniformity Coefficient of Stress Distribution in Failure Section of Wood - like Composite Beam - Column Member

ABSTRACT

In this paper, several models of stress-strain relationship of clear wood were firstly introduced :from loading to failure, tensile stress-strain relationship is always consistent with Hooke's law, exhibiting perfect linear behavior; while the PSB is under compression, the stress varies linearly with the change of strain when the stress is within the proportional limit, once the stress exceeds the limit, the stress-strain curve turned into nonlinear behavior and the slope of it was monotonically decreased. After reaching the peak point, the compressive stress began to decrease and the curve of which the slope became negative turned to descending branch. In this paper, two quadratic functions with different coefficients were used to represent the stress-strain relationship of PSB in plastic strengthening and softening period. It is important for the elastic - plastic analysis of beam - column members to make the constitutive law of this material clear, which is also the basis of theoretical analysis and the deduction of formulas.

Secondly, the theory of Euler beam and beam - column theory were summarized, based on which the elastic - plastic analysis model of PSB beams was carried out via four-point bending tests. Considering the softening of the material in the compression stage, the formula of the uniformity distribution coefficient of the stress distribution of the failure section was deduced, and the formula of ultimate loading-capacity and deformation of the beams were given. The theoretical calculation values were compared with the test results, thus verifying the accuracy and feasibility of the re-defined coefficient.

Key words：Wood-like composite；Constitutive law；Beam-column theory；4-point bending test；Coefficient；

目 录

1 绪论 1

1.1 类木复合材料 1

1.1.1 实木（Solid Wood） 1

1.1.2 木质复合材料（Wood-based Composite） 2

1.1.3 竹质复合材料（Bamboo-based Composite） 6

1.2 现行规范中梁-柱构件的设计方法 7

1.3 类木复合材料破坏截面应力分布均匀性系数研究概况 9

2 类木复合材料本构关系概述 10

2.1 木材应力-应变关系模型概述 10

2.1.1 应力-应变关系曲线简化发展过程 10

2.1.2 应力-应变关系曲线数学表示概述 11

2.2 重组竹应力-应变关系模型 14

2.2.1 顺纹受拉 14

2.2.2 顺纹受压 15

2.2.3 重组竹的应力-应变关系数学表达式 15

3 梁-柱理论 18

3.1 欧拉-伯努利梁理论 18

3.2 铁木辛柯梁理论 20

3.3 梁-柱理论 20

4 破坏截面应力分布均匀性系数 24

4.1 重组竹梁的四点弯曲试验概述 24

4.2 截面各区段高度的确定 25

4.3 不考虑塑性软化阶段的均匀性系数 27

4.3.1 应力分布均匀性系数的定义 27

4.3.2 受弯构件极限承载力和变形 28

4.4 考虑塑性软化阶段的均匀性系数 30

4.4.1 应力分布均匀性系数的定义 30

4.4.2 受弯构件极限承载力和变形 31

4.5 试验验证 33

4.6 本章小结 35

5 总结与展望 37

5.1 总结 37

5.2 展望 37

致 谢 39

参考文献 40

绪 论

类木复合材料

近年来，出于对自然环境的关心和保护，以及国际社会节能减排的要求，越来越多的工程中开始尝试使用竹、木作为结构材料。但是，由于其力学性能和几何形状尺寸种类繁多且差异性较大，传统的竹、木产品不能满足现代建筑结构的要求，仅被用于建筑装饰材料。

首先提出类木复合材料(Wood-like Composite，简称WLC)这一名词，目前研究的类木复合材料包括:实木、木基复合材料、竹基复合材料。因为它们具有相似的泡沫-纤维微观结构和明显的横向各向同性正交异性以及拉压非对称而归为一类材料。类木复合材料具有更加优越的性能，通过设计和计算，可以将其作为建筑材料应用于建筑结构中。下面将分别展开介绍这三部分材料。

实木（Solid Wood）