結(jié)構(gòu)力學(xué)：雙語(yǔ)教材

編者的話

本書被列入武漢大學(xué)“十五”規(guī)劃教材，系武漢大學(xué)出版社組織出版的21世紀(jì)高等學(xué)校土木工程類系列教材之一，在2002年底投入編寫。本著勇于探索、有所創(chuàng)新的原則，書中在以下幾個(gè)方面作了新的嘗試和安排：

一、以原結(jié)構(gòu)力學(xué)專業(yè)英語(yǔ)教材為基礎(chǔ)，增加了實(shí)質(zhì)性的解題內(nèi)容和理論分析，有別于原結(jié)構(gòu)力學(xué)專業(yè)英語(yǔ)教材的閱讀材料性質(zhì)。

二、參考了大量的國(guó)內(nèi)外同類教材，在編排上盡量與本科結(jié)構(gòu)力學(xué)教學(xué)的格局相同，并作了比較性的探索，對(duì)于同一教學(xué)內(nèi)容，加進(jìn)了國(guó)外教材與本國(guó)教材不同的解題方法。

三、把提高學(xué)生的英語(yǔ)水平也作為本教材的目的之一，加進(jìn)了科技英語(yǔ)的口語(yǔ)表達(dá)，此外還增加了數(shù)學(xué)公式和圖表的文字表述(這由教師在課堂教學(xué)中體現(xiàn))。

教材建設(shè)工作需要長(zhǎng)期積累，同時(shí)又需要不斷總結(jié)和翻新。本書作為正式教材出版，還是第一次，其中多有不盡如人意的地方，懇請(qǐng)各方指正。

本書由袁文陽(yáng)統(tǒng)籌，周劍波選材，歷時(shí)一年編寫完成。陳亞鵬和周艷國(guó)參與了校對(duì)工作。

感謝武漢大學(xué)出版社的李漢保老師、謝群英老師的熱情支持和大力協(xié)助。

編 者

2004年3月于珞珈山

書摘

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．

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本書是武漢大學(xué)“十五”教材計(jì)劃選定的雙語(yǔ)教材，是二十年來(lái)結(jié)構(gòu)力學(xué)專業(yè)英語(yǔ)教材基礎(chǔ)上的新成果。全書共13章，基本涵蓋了本科結(jié)構(gòu)力學(xué)的經(jīng)典內(nèi)容，書中附有少量的習(xí)題，便于學(xué)生自學(xué)并促使其閱讀更多的參考書以輔助學(xué)習(xí)。

本書適用于土木、水利等本科專業(yè)的結(jié)構(gòu)力學(xué)雙語(yǔ)教學(xué)。

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

《普通高等院校雙語(yǔ)教材:工程測(cè)量》可作為普通高等院校工程測(cè)量、土木建筑、公路交通等專業(yè)的雙語(yǔ)教材、有關(guān)專業(yè)研究生的參考書，也可供從事測(cè)繪教學(xué)與生產(chǎn)人員作為英語(yǔ)學(xué)習(xí)資料使用。

1.結(jié)構(gòu)力學(xué)（龍馭球 高等教育出版社）

2.結(jié)構(gòu)分析（杜正國(guó) 高等教育出版社）

3.結(jié)構(gòu)力學(xué)（李廉錕 高等教育出版社）

4.結(jié)構(gòu)力學(xué)教程（杜正國(guó) 西南交通大學(xué)出版社）

5.結(jié)構(gòu)力學(xué)（朱慈勉 高等教育出版社）

6.結(jié)構(gòu)力學(xué)（王煥定 高等教育出版社）

7.結(jié)構(gòu)力學(xué)（楊耀乾 高等教育出版社）

8.結(jié)構(gòu)力學(xué)練習(xí)冊(cè)(彭俊生 西南交通大學(xué)出版社)

9.Structural Mechanics (Bao Shihua，WHUT Press)

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