2024年4月28日发(作者：)

外文翻译

结构设计

结构设计

Augustine ch

摘要：

结构设计是选择材料和构件类型，大小和形状以安全有用的样式承

担荷载。一般说来，结构设计暗指结构物如建筑物和桥或是可移动但有刚性外壳

如船体和飞机框架的工厂稳定性。设计的移动时彼此相连的设备（连接件），一

般被安排在机械设计领域。

关键词

：

结构设计 ； 结构分析 ； 结构方案 ； 工程要求

Abstract: Structure design is the selection of materials and member type ,size,

and configuration to carry loads in a safe and serviceable fashion .In

general ,structural design implies the engineering of stationary objects such as

buildings and bridges ,or objects that maybe mobile but have a rigid shape such as

ship hulls and aircraft frames. Devices with parts planned to move with relation to

each other(linkages) are generally assigned to the area of mechanical .

Key words: Structure Design ； Structural analysis ；structural scheme ；

Project requirements

Structure Design

Structural design involved at least five distinct phases of work: project

requirements, materials, structural scheme, analysis, and design. For unusual

structures or materials a six phase, testing, should be included. These phases do not

proceed in a rigid progression , since different materials can be most effective in

different schemes , testing can result in change to a design , and a final design is often

reached by starting with a rough estimated design , then looping through several

cycles of analysis and redesign . Often, several alternative designs will prove quite

close in cost, strength, and serviceability. The structural engineer, owner, or end user

would then make a selection based on other considerations.

Project requirements. Before starting design, the structural engineer must

determine the criteria for acceptable performance. The loads or forces to be resisted

must be provided. For specialized structures, this may be given directly, as when

supporting a known piece of machinery, or a crane of known capacity. For

conventional buildings, buildings codes adopted on a municipal, county , or , state

level provide minimum design requirements for live loads (occupants and furnishings ,

snow on roofs , and so on ). The engineer will calculate dead loads (structural and

known, permanent installations ) during the design process.

For the structural to be serviceable or useful , deflections must also be kept

within limits ,since it is possible for safe structural to be uncomfortable “bounce”

Very tight deflection limits are set on supports for machinery , since beam sag can

cause drive shafts to bend , bearing to burn out , parts to misalign , and overhead

cranes to stall . Limitations of sag less than span /1000 ( 1/1000 of the beam length )

are not uncommon . In conventional buildings, beams supporting ceilings often have

sag limits of span /360 to avoid plaster cracking, or span /240 to avoid occupant

concern (keep visual perception limited ). Beam stiffness also affects floor

“bounciness,” which can be annoying if not controlled. In addition , lateral deflection ,

sway , or drift of tall buildings is often held within approximately height /500 (1/500

of the building height ) to minimize the likelihood of motion discomfort in occupants

of upper floors on windy days .

Member size limitations often have a major effect on the structural design. For

example, a certain type of bridge may be unacceptable because of insufficient under

clearance for river traffic, or excessive height endangering aircraft. In building design,

ceiling heights and floor-to-floor heights affect the choice of floor framing. Wall

thicknesses and column sizes and spacing may also affect the serviceability of various

framing schemes.

Materials selection. Technological advances have created many novel materials

such as carbon fiber and boron fiber-reinforced composites, which have excellent

strength, stiffness, and strength-to-weight properties. However, because of the high

cost and difficult or unusual fabrication techniques required , they are used only in

very limited and specialized applications . Glass-reinforced composites such as

fiberglass are more common, but are limited to lightly loaded applications. The main

materials used in structural design are more prosaic and include steel, aluminum,

reinforced concrete, wood , and masonry .

Structural schemes. In an actual structural, various forces are experienced by

structural members , including tension , compression , flexure (bending ), shear ,and

torsion (twist) . However, the structural scheme selected will influence which of these

forces occurs most frequently, and this will influence the process of materials

selection.

Tension is the most efficient way to resist applied loads ,since the entire

member cross section is acting to full capacity and bucking is not a concern . Any

tension scheme must also included anchorages for the tension members . In a

suspension bridge , for example ,the anchorages are usually massive dead weights at

the ends of the main cables . To avoid undesirable changes in geometry under moving

or varying loads , tension schemes also generally require stiffening beams or

trusses.

Compression is the next most efficient method for carrying loads . The full

member cross section is used ,but must be designed to avoid bucking ,either by

making the member stocky or by adding supplementary bracing . Domed and arched

buildings ,arch bridges and columns in buildings frames are common schemes .

Arches create lateral outward thrusts which must be resisted . This can be done by

designing appropriate foundations or , where the arch occurs above the roadway or

floor line , by using tension members along the roadway to tie the arch ends

together ,keeping them from spreading . Compression members weaken drastically

when loads are not applied along the member axis , so moving , variable , and

unbalanced loads must be carefully considered.

Schemes based on flexure are less efficient than tension and compression ,since

the flexure or bending is resisted by one side of the member acting in tension while

the other side acts in compression . Flexural schemes such as beams , girders , rigid

frames , and moment (bending ) connected frames have advantages in requiring no

external anchorages or thrust restrains other than normal foundations ,and inherent

stiffness and resistance to moving ,variable , and unbalanced loads .

Trusses are an interesting hybrid of the above schemes . They are designed to

resist loads by spanning in the manner of a flexural member, but act to break up the

load into a series of tension and compression forces which are resisted by individually

designed tension and have excellent stiffness and resistance to moving and variable

loads . Numerous member-to-member connections, supplementary compression

braces ,and a somewhat cluttered appearance are truss disadvantages .

Plates and shells include domes ,arched vaults ,saw tooth roofs , hyperbolic

paraboloids , and saddle shapes .Such schemes attempt to direct all force along the

plane of the surface ,and act largely in shear . While potentially very efficient ,such

schemes have very strict limitations on geometry and are poor in resisting

point ,moving , and unbalanced loads perpendicular to the surface.

Stressed-skin and monologue construction uses the skin between stiffening

ribs ,spars ,or columns to resist shear or axial forces . Such design is common in

airframes for planes and rockets, and in ship hulls . it has also been used to advantage

in buildings. Such a design is practical only when the skin is a logical part of the

design and is never to be altered or removed .

For bridges , short spans are commonly girders in flexure . As spans increase

and girder depth becomes unwieldy , trusses are often used ,as well as cablestayed

schemes .Longer spans may use arches where foundation conditions ,under

clearance ,or headroom requirements are favorable .The longest spans are handled

exclusively by suspension schemes ,since these minimize the crucial dead weight and

can be erected wire by wire .

For buildings, short spans are handled by slabs in flexure .As spans increase,

beams and girders in flexure are used . Longer spans require trusses ,especially in

industrial buildings with possible hung loads . Domes ,arches , and cable-suspended

and air –supported roofs can be used over convention halls and arenas to achieve clear

areas .

Structural analysis . Analysis of structures is required to ensure stability (static

equilibrium ) ,find the member forces to be resisted ,and determine deflections . It

requires that member configuration , approximate member sizes ,and elastic modulus ;

linearity ; and curvature and plane sections . Various methods are used to complete the

analysis .

Final design . once a structural has been analyzed (by using geometry alone if

the analysis is determinate , or geometry plus assumed member sizes and materials if

indeterminate ), final design can proceed . Deflections and allowable stresses or

ultimate strength must be checked against criteria provided either by the owner or by

the governing building codes . Safety at working loads must be calculated . Several

methods are available ,and the choice depends on the types of materials that will be

used .

Pure tension members are checked by dividing load by cross-section area .Local

stresses at connections ,such as bolt holes or welds ,require special attention . Where

axial tension is combined with bending moment ,the sum of stresses is compared to

allowance levels . Allowable : stresses in compression members are dependent on the

strength of material, elastic modulus ,member slenderness ,and length between

bracing points . Stocky members are limited by materials strength ,while slender

members are limited by elastic bucking .

Design of beams can be checked by comparing a maximum bending stress to

an allowable stress , which is generally controlled by the strength of the material, but

may be limited if the compression side of the beam is not well braced against

bucking .

Design of beam-columns ,or compression members with bending moment ,must

consider two items . First ,when a member is bowed due to an applied

moment ,adding axial compression will cause the bow to increase .In effect ,the axial

load has magnified the original moment .Second ,allowable stresses for columns and

those for beams are often quite different .

Members that are loaded perpendicular to their long axis, such as beams and

beam-columns, also must carry shear. Shear stresses will occur in a direction to

oppose the applied load and also at right angles to it to tie the various elements of the

beam together. They are compared to an allowable shear stress. These procedures can

also be used to design trusses, which are assemblies of tension and compression

members. Lastly, deflections are checked against the project criteria using final

member sizes.

Once a satisfactory scheme has been analyzed and designed to be within project

criteria, the information must be presented for fabrication and construction. This is

commonly done through drawings, which indicate all basic dimensions, materials,

member sizes, the anticipated loads used in design, and anticipated forces to be

carried through connections.

结构设计

结构设计包含至少5个不同方面的工作：工程要求，材料，结构方案，分析

和设计。对于不一般的结构或材料，又包含一个方面：试验。这些方面不是严格

按步骤进行，因为不同材料在不同方案大多数是有效的，试验会导致设计变更，

最终设计由初步估计设计开始，然后经过分析和再设计几个循环后完成。通常，

可替代的设计证明在费用，强度和使用性上十分接近。结构工程师，业主或最后

住户基于其它的考虑选择一种。

工程要求。在开始设计前，结构工程师必须决定容易接受的执行标准。必须

提供承担的荷载或力。对于一些专门结构，当支持一台已知载重的机器或起重机

时，这可能直接给出，对于普通建筑物，采用市政，县，州的建筑规范，提供了

设计所需活载（人群荷载和设备，屋顶雪荷载，等等）的最小值。工程师将计算

出设计期间的恒载（结构和已知永久性设备）。

对要正常使用的结构，也必须控制其挠度，因为安全的结构可能会存在令人

不安的振动。机器的支座有严格的变形限制，因为梁下沉会导致驱动轴弯曲，烧

毁，部件错位和上面的吊车熄火。挠度限制在跨度/1000 (梁长的1/1000）以下

是很普通的。在传统建筑里，支持板的梁挠度限制在跨度1/360以避免粉刷开裂

或跨度1/240以避免人的担忧（保持在可感知的变动范围内）。梁的刚度也影响

板“振动”，如果不能控制会令人很头疼。另外，高层建筑的侧面变形，位移或

摇摆通常限定在高度/500（建筑物高度的1/500）里，把在有风的日子里上面楼

层的人移动的不舒服降到最小。构件尺寸在结构设计里起主要作用。例如，由于

下面留作水上交通的净空不够或过高威胁到飞机的特定类型的桥是不可接受的。

在建筑设计里，天花板高度和楼板之间高度影响楼板框架的选择。墙厚和柱子尺

寸和跨度也影响不同框架方案的适用性。

选择材料。技术的进步创造了许多新材料，如碳纤维加强复合材料和硼纤维

加强复合材料，它们都具有极好的强度，刚度和强度重量比特性。然而，由于费

用高和非通常的制造要求，它们仅用在有限特殊领域。强化玻璃合成物如玻璃纤

维是很普遍，但被限制应用在小荷载情况下。用在结构设计上的主要材料更多是

普通的，包括钢材，铝，钢筋混凝土，木材，砌体。

结构方案。在一个实际方案里，结构构件承担很多力，包括拉，压，弯，剪

和扭。然而所选择的方案将会影响这些力产生的概率，也会影响材料选择过程。

抗拉是有效的承担荷载的方法，整个构件的横截面性能得到发挥，并且不涉

及到弯曲变形。任何抗拉方案必须也对抗拉构件的锚固。例如，在悬索桥里，锚

固体通常是位于主要绳索尾段的强大自重。为了避免在荷载移动或变形时有不期

望的几何变形，抗拉方案通常要求是刚性梁和桁架。

抗压是另一个很有效的承担荷载方法。全部杆件截面发挥了作用，但是设计

时必须避免弯曲，或者是做成粗短构件或者是增加附加支撑。圆顶和拱形建筑，

拱桥和柱是很普遍的建筑方案。拱产生了必须抵挡住的水平外推力。这靠设计合

适的基础或建在车道或楼板的上面的拱解决，靠沿着车道用抗拉构件把两端的拱

连接起来，阻止他们拉开。当荷载不是作用在构件轴线上时，抗压构件显著地被

削弱。所以，必须认真考虑移动，变化和不平衡的荷载。

基于受弯的方案的效率比受拉和压低，因为弯曲是靠构件一边受拉另一边受

压来抵抗。受弯方案如主梁，次梁，刚架和受弯框架在外部锚固或推力限制，与

一般基础不同，靠内部刚度阻挡可移动，变化和不平衡的荷载的情况下有利。

桁架是上面方案的混合体。它们设计成荷载横跨在受弯构件上，但是分解成

一系列拉力和压力，由抗拉和抗压构件承担。桁架方案设计时不需要特殊锚固或

推力的限制，并且有很好的刚度抵抗移动或变化的荷载。大量的构件之间连结和

抗压构件的附加支撑，看起来有点杂乱，这就是桁架的不利处。

板和壳包括圆顶，拱顶，有齿屋顶，双曲抛物面和马鞍形。这样的方案把所

有的力直接作用在平板表面并且作用有巨大的剪力。尽管可能效率很高，但是这

样的方案对几何有严格的限制，并且在移动，和不平衡垂直作用在表面的荷载的

能力很弱。

薄壳结构和硬壳结构利用加劲肋，梁之间的壳板抵抗剪力和轴向力。这样的

设计在飞机机体和火箭，船体方面很普遍。它在建筑方面也是有利的。这样的设

计仅仅在壳是设计的逻辑部分并且永远不会被替代和移除时才实际些。

对于桥梁，短跨是很普遍受弯的梁。当跨度增加和梁高变得很大时，通常用

桁架和斜拉结构。更长跨时也许用拱，要考虑基础条件和净空要求。最长的跨靠

悬索方案处理，因为这可把关键性的自重降到最小并且能索连索地建造起来。

对于桥，短跨靠板承担弯矩。当跨度增加时，主梁和次梁被用来承担弯曲。

更长的跨要求用桁架，尤其是在工业建筑有吊车荷载时，圆顶，拱和悬索和充气

屋顶被用在传统的大厅和竞技场里以获得净面积。

结构分析。结构分析要求确定稳定性（静力平衡），构件承担的力和变形。

它需要构件形状，大概尺寸，已知或假设的材料特性。分析包括：平衡，应力，

应变和弹性模量，线形，塑性和弯曲和板截面。很多方法可以完成分析过程。

最终设计。一旦结构分析完成（如果分析是正确的，只用几何方法；反之附

加构件尺寸和材料假设）。最终设计可以进行，必须对照业主或政府建筑规范标

准来检查变形和允许应力或极限强度。必须计算工作荷载下的安全性。一般方法

是可行的，依据所使用的材料类型做出选择。

纯抗拉构件检查横截面应力。特别注意螺栓孔或焊接处的应力。拉弯构件中，

用应力之和与分析应力作比。受压构件中的允许应力取决于构件强度，弹性模量，

长细比和支点间距离。粗短构件由材料强度决定，然而长细构件由弹性弯曲决定。

梁的设计由对于最大弯曲应力和允许应力来检验，通常由材料强度控制，但

是如果受压一边没有侧向支撑就会被限制。

梁，柱或有弯矩的受压构件的设计必须考虑两项。首先，当构件由于承受弯

矩而弯曲时，轴力会增加弯曲量，实际上，轴压放大了原始弯矩。其次，对于柱

和梁的允许应力是不同的。

承受垂直于长轴的荷载的构件。如梁和梁——柱，也必须承担剪力。剪应力

和荷载的方向相反并且在其右边，把梁的不同部分连接起来。它们与允许剪应力

作对比。这些步骤也能用来设计由受拉和受压构件组成的桁架。最后，用工程标

准检验变形，使用最后的构件。

一旦被分析和在工程标准内的设计方案是令人满意的，必须提出制造和建立

信息。通过作图，指明所以基本尺寸，材料和构件大小。设计中预期荷载和节点

承担的预期力。