重组竹压弯构件破坏区塑性铰长度探讨毕业论文

 2021-04-16 01:04

摘 要

压弯构件是指承受轴力和弯矩共同作用的结构构件,具体包括单向压弯构件、双向压弯构件及偏压构件[1]。本文以重组竹单偏压柱构件作为研究对象,在重组竹结构设计体系中,单偏压柱构件承载力及挠度计算公式的推导虽已有突破,但仍需更加深入、精确的研究。通过理论分析及公式推导可知:获得重组竹柱构件单偏压下极限承载力的最终任务为:明确其跨中最大挠度。跨中最大挠度包括由弹性变形引起的弹性挠度和由塑性变形即塑性铰转动引起的塑性挠度两部分。其中:弹性挠度可由梁-柱理论[2]直接算得,而塑性挠度则需在明确塑性铰长度的基础上通过推导得出。规定极限状态下,所有处于非线性软化阶段截面点所在的区段长度为塑性铰长度。黄东升等[3-6]在以往的公式推导过程中认为:塑性铰的长度很短,可近似等于柱构件跨中截面宽度,并以此为基础,给出了挠度计算的理论公式。为佐证其假设的正确性,本文将以目前学者于塑性铰长度计算方面的研究成果为基础,通过建立弯矩等量方程,获得满足规定要求的应力分布起止点位置,最终通过起止点差值确定塑性铰长度,为重组竹柱构件的结构设计提供更加精确的理论基础,亦为重组竹材在今后建筑结构体系中的推广提供更为有效的依据。

关键词:重组竹;结构分析;等量方程;塑性铰长度

The Plastic Hinge Length of Parallel Strand Bamboo (PSB) Columns Under Eccentrically Compressive Load

ABSTRACT

The component under axial compressive load and bending moment is known as compression-bending member, including uniaxial bending moment, bi-axial bending moment and eccentrically compressed members. The study mainly focus on the Parallel Strand Bamboo (PSB) that subjected to eccentrically compressive load, especially on the deduction of capacity and deflection formula. However, current research on PSB in structure technology system is superficial, in which the ultimate bearing capacity and deflection of its column members under eccentrically compressive load still need more lucubration and precise consideration. From the theoretical analysis and derivation of formula, we can know that the final task of identifying the ultimate bearing capacity of PSB columns under eccentrically compressive load is to ascertain the maximum deflection of middle span. In addition, the maximum deflection mainly includes two aspects, elastic flexibility induced by elastic deformation and plastic flexibility induced by plastic deformation (the rotation of the plastic hinges). The former can be calculated directly based on the beam-column theory, the latter can be deducted only when we know the plastic hinge length, which is defined as the length containing all the points that have come into non-linear softening stage at the ultimate state. D.S.Huang provided a novel review that the plastic hinge length is so small that we can regard it as the mid-span’s breadth of section, and demonstrated the theoretical formula of deflection based on his assumption. In order to support the views of D.S.Huang, the author established the bending-moment equation based on other scholars’ achievements, obtaining the start-stop point of stress distribution that meet the demands, identifying the plastic hinge length by calculate the difference of the start-stop point. The research not only provides more exact theoretical basis for the design of PSB columns, but offers more effective experience for the popularization of PSB.

Keywords: Parallel Strand Bamboo (PSB); Structure analysis; Bending-moment equation; Plastic Hinge Length.

目 录

1 绪论………………………………………………………………………………………………………1

1.1 引言…………………………………………………………………………………………………1

1.2 研究背景综述………………………………………………………………………………………2

1.2.1 重组竹材概述………………………………………………………………………………2

1.2.2 压弯构件受力性能概述……………………………………………………………………4

1.2.3 塑性铰长度计算方法概述…………………………………………………………………8

1.3 本文主要研究任务………………………………………………………………………………10

1.3.1 研究对象及内容……………………………………………………………………………10

1.3.2 研究方法及组织安排………………………………………………………………………11

2 重组竹顺纹向本构理论…………………………………………………………………………………13

2.1 概述………………………………………………………………………………………………13

2.2 材料基本本构模型………………………………………………………………………………14

2.2.1 线弹性本构模型……………………………………………………………………………15

2.2.2 弹塑性本构模型……………………………………………………………………………15

2.3 重组竹弹塑性应力-应变关系……………………………………………………………………17

2.3.1 破坏机理……………………………………………………………………………………17

2.3.2 本构方程……………………………………………………………………………………19

2.4 强度理论…………………………………………………………………………………………20

2.4.1 最大应力及最大应变理论…………………………………………………………………21

2.4.2 von-Mises理论………………………………………………………………………………21

2.4.3 Tsia-Hill准则………………………………………………………………………………21

2.4.4 Hoffman准则………………………………………………………………………………22

2.5 本章小结…………………………………………………………………………………………23

3 重组竹单向压弯中长柱性能分析………………………………………………………………………24

3.1 概述………………………………………………………………………………………………24

3.2 中长柱受力特性…………………………………………………………………………………24

3.3 极限承载力分析…………………………………………………………………………………25

3.3.1 现有承载力计算公式………………………………………………………………………26

3.3.2 考虑软化下降段承载力公式推导…………………………………………………………27

3.4 挠度分析…………………………………………………………………………………………30

3.4.1 分析方法……………………………………………………………………………………30

3.4.2 侧向挠度计算公式…………………………………………………………………………32

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