编者的话

本书被列入武汉大学“十五”规划教材，系武汉大学出版社组织出版的21世纪高等学校土木工程类系列教材之一，在2002年底投入编写。本着勇于探索、有所创新的原则，书中在以下几个方面作了新的尝试和安排：

一、以原结构力学专业英语教材为基础，增加了实质性的解题内容和理论分析，有别于原结构力学专业英语教材的阅读材料性质。

二、参考了大量的国内外同类教材，在编排上尽量与本科结构力学教学的格局相同，并作了比较性的探索，对于同一教学内容，加进了国外教材与本国教材不同的解题方法。

三、把提高学生的英语水平也作为本教材的目的之一，加进了科技英语的口语表达，此外还增加了数学公式和图表的文字表述(这由教师在课堂教学中体现)。

教材建设工作需要长期积累，同时又需要不断总结和翻新。本书作为正式教材出版，还是第一次，其中多有不尽如人意的地方，恳请各方指正。

本书由袁文阳统筹，周剑波选材，历时一年编写完成。陈亚鹏和周艳国参与了校对工作。

感谢武汉大学出版社的李汉保老师、谢群英老师的热情支持和大力协助。

编 者

2004年3月于珞珈山

书摘

6.3 Assumptions for Truss Analysis

The following assumptions are made in order to simplify the analysis of trusses:

I. Truss members are connected together with frictionless pins. (Pin connections are used for very few trusses erected today, and no pins are frictionless. A heavy bolted or welded joint is a far cry from a frictionless pin. )

2. Truss members are straight. ( If they were not straight, the axial forces would cause them to have bending moments).

3. The deformations of a truss under load, caused by the changes in lengths of the individual members, are not of sufficient magnitude to cause appreciable changes in the overall shape and dimensions of the truss. Special consideration may have to be given to some very long and flexible trusses.

4. Members are so arranged that the loads and reactions are applied only at the truss joints.

Examination of roof and bridge trusses will prove this last statement to be generally true, in buildings with roof trusses the beams, columns, and bracing frame directly into the truss joints. Roof loads are transferred to trusses by horizontal beams, called pudins, which span the distance between the trusses. The roof is supported directly by the purlins or it is supported by rafters, or

subpurlins, which run parallel to the trusses and are supported by the purlins. The purling are placed at the truss joints unless the top-chord panel lengths become case it is sometimes economical to place purlins in between the joints

exceptionally long, in which although some bending will be developed in the top chords. ( Some types of roofing, such as corrugated steel, gypsum slabs, and others may he laid directly on the purling. The purlins then have to be spaced at intermediate points along the top chord so as to provide a proper span for the roofing they directly supports. )

6.4 Effect of Assumptions

The effect of the foregoing assumptions is to produce an ideal truss. Whose members have only axial forces. A member with axial force only is subject to a push or pull with no bending present. (Even if all of the assumptions were perfectly true, there would be some bending in a

member caused by its own weight. )

Forces obtained on the basis of these simplifying assumptions are very satisfactory in most

cases and are referred to as primary forces. Structures are sometimes ~alysed without the aid of

some or all of these assumptions. Forces cauTed by conditions not considered in the primary force

analysis are said to be secondary forces.

6．5 Truss Analysis

An indispensable part of truss analysis，a8 in beam analysis， isthesepamtion 0f the tmss into two part8 with an imaginary section．The part of the truss on one 8ideof the section is removed and studied independendy．The loads applied to this free body include the axial f10rces 0f the members that have been cut by the sectio’n and any loads and reaction8 that may be applied

externally．

Application of the equations of statics to isolated free bodies enable8 one to determine the forces in the cut members if the free bodies are carefully selected 80 thatthe 8ection8 do not Dass through too many members whose forces are unknown．There are only three equations of statics。and no more than three unknowns may be determinedfromany one section．

After he or she has analyzed a few trusses，thestudentwillhavelittledifficuIty in m08t case in selecting satisfactory locations for the sections．The studenti8notencouraged t0 remembe specific sections for specific trusses，althoughheorshewillprobablyunconsciously faU int0 suc a habit as time goes by． At this stage the student needs to consider each case individuallv withou reference to other，similar trusses．

It is convenient to work with horizontal and veRicalcomponentsinthecomputation of ferces

oftrussmembers,as in the c。mputati。n。f reacti。ns．The∑日=0 and∑V=Oequations。 statics are generally written on the basis of a pair of axes that are herizontal and venical． Because the forces in truss members are determined successively across a truss，much time will be 8aved if the vertical and horizontal components of forces in inclined members are recorded for u8e in applying the equations to other members．The use of components i8 cleady illu8trated in the example problems of sections that lollow．

6．6 Arrow Convention

The sign COnvrention for ten8ile and COmpres8ive forces( and一re8pectively)has already been mentioned·Arrows are also used throughout the text torepresentthecharacter 0f forces．The armw8 indicate what members are doing to resist the axial forces applied t0tllem by tlle remainder

0f the truss·For example，if a truss is compressing a certain member from each end(- 一 -)。 the member will push back against the compressive forces．convention i8 ued for members in compression．

……2100433B

本书是武汉大学“十五”教材计划选定的双语教材，是二十年来结构力学专业英语教材基础上的新成果。全书共13章，基本涵盖了本科结构力学的经典内容，书中附有少量的习题，便于学生自学并促使其阅读更多的参考书以辅助学习。

本书适用于土木、水利等本科专业的结构力学双语教学。

CHAPTER 1 Introduction

CHAPTER 2 Stability

CHAPTER 3 Bending of Beams

CHAPTER 4 Statical ly Determ inate Frames

CHAPTER 5 Three Hinged Arches

CHAPTER 6 Truss Analysis

CHAPTER 7 Displacement and VirtuaI Work

CHAPTER 8 Influence Lines

C!HAPTER 9 Flexibility Method

CHAPTER 10 Sti仟ness Method

CHAPTER 11 Moment Distribution

C：HAPTER 12 The Finite Element Analysis

CHAPTER 13 Structural Dynamics

References

《普通高等院校双语教材:工程测量》可作为普通高等院校工程测量、土木建筑、公路交通等专业的双语教材、有关专业研究生的参考书，也可供从事测绘教学与生产人员作为英语学习资料使用。

1.结构力学（龙驭球 高等教育出版社）

2.结构分析（杜正国 高等教育出版社）

3.结构力学（李廉锟 高等教育出版社）

4.结构力学教程（杜正国 西南交通大学出版社）

5.结构力学（朱慈勉 高等教育出版社）

6.结构力学（王焕定 高等教育出版社）

7.结构力学（杨耀乾 高等教育出版社）

8.结构力学练习册(彭俊生 西南交通大学出版社)

9.Structural Mechanics (Bao Shihua，WHUT Press)

10.Structural Analysis （R.C.Hibbeler） 2100433B