05 Chapter 5 Load and Design Process.pptx

第1页：建筑规范与设计依据

Chapter 5 Load and Design ProcessSection A PrinciplesofStructureDesignAn architect draws up plans for a building to meet theclient’srequirements. The structural engineer examinesvarious arrangements and carries outpreliminarydesigns todetermine which is the most economical.All structural design iscontrolled by spcifications. Even if no limitation is placed uponthe designer, he will still be very likely to depend upon astandard set of specifications for guidance.

建筑师画建筑图以满足客户的需求。

结构师检查不同的布置并进行初步设计以确定那一个方案最经济。所有的结构设计都由规范控制，即使没有限制，设计师也非常可能依靠一套标准的设计说明书作指导。

第2页：建筑规范的技术要求

All large cities have buildingcodesthat specify not onlyworking stress but also other features of other structures.Astandard set of specifications may be accepted to representthe best information available on the subject. The designerwill follow the specifications of the local building code bynecessity. All structures must be designed to support loadswithout danger of overall collapse or failure of thecomponents.

所有的大城市都有建筑规范，这些规范不仅指定了工作应力，而且还有结构的其它特征。

一套标准的技术规范代表了最实用的专业信息，设计时必须遵守当地建筑规范的技术说明。所有结构的设计都要能够承担荷载而不会有整体倒塌或构件破坏的危险。

第3页：塑性设计方法

Theplasticdesigniswhollydependentforitsvalidityupontheformationofplastichingesrequiringconsiderableductilityofthematerial.Byuseofanappropriatefactorofsafetyinplasticdesign,onemaydesignordinarycontinuousbeamsandframesforcollapseloadingwithfullconfidencethatalogicalandbalanceddesignwillbeachieved.

塑性设计方法完全依赖于塑性铰的形成，这要求材料有相当大的塑性。

在塑性设计中，通过使用和适的安全系数，设计师可以按破坏荷载来设计普通的连续梁和框架，同时满怀信心地实现一个合理而平衡的设计。

第4页：结构设计的四个步骤

For a given arrangement, the problem in structural design is1、Estimation of loading2、Determination of stresses and strains in structures3、Design of elements andjoints4、Production of arrangement and drawings

对于给定的布置，在结构设计中存在的问题是：1.荷载的估计2.结构中应力和应变的确定3.构件和节点的设计4.布置和图纸的形成

第5页：荷载的不确定性

One of the undeterminable factors in design may be theloading itself. Dead load can be estimated quite accurately,but live loading, wind, impact, sway, and otherinertiaforces are extremely variable.

设计中的不确定因素之一可能就是荷载本身。

静荷载可以估计得相当准确，但活荷载、风荷载、冲击荷载、摇摆和其它惯性力的变化非常大。

第6页：荷载效应与结构抗力

Designer over the years have attempted to achievestructural safety by ensuring that the effects of the appliedloads on structures will not exceed the resistance orcapacityof the structural members and connections, with a certainmarginof safety. It may be expressed asLoad effects Q≤ Resistance R

过去几年来，设计师尝试借助于某一安全系数，通过确保结构上施加的荷载效应不超过结构构件或连接的抵抗能力来获得结构的安全。这可以表示为：荷载效应Q≤结构抗力R

第7页：设计不等式的发展完善

This inequality is the basis for the design methods thathave been continuously improved over many decades throughresearch and development in materials, design procedures,analytical techniques, computer applications, erection andfabrication methods, structural performances and constructionexperience.

这个不等式是设计的依据，在过去几十年通过对材料、设计方法、分析手段、计算机应用、建造和安装方法、结构性能和施工经验等的研究和发展不断得到改进。

第8页：容许应力法与LRFD法

Thereareseveralmethodsinstructuraldesign.AllowableStressDesign(ASD),LoadandResistanceFactorDesign(LRFD)arewithinit.ASDmethodhasbeeninusesincebeforethe1900s.

在结构设计中有几种方法。

容许应力设计法（ASD），荷载与抗力系数设计法（LRFD）便是其中之一。ASD法从90年代之前就在使用。

第9页：荷载抗力系数设计法

LRFD is a method of proportioning structural membersusing load and resistance factors, so no applicable limit stateis reached when the structure is subjected to all appropriateload combinations.It is based on new developments instructural engineering. It incorporates the best of allowable orworking stress design, strength design, load-factor designand plastic design, which are already familiar to designers.LRFD法是一种成比例的结构构件采用荷载和抗力系数的方法，因此结构在所有适当的荷载组合下不会达到极限状态。LRFD

法是以结构工程的最新研究为基础，它是容许或工作应力设计、强度设计、荷载系数设计及塑性设计的最好的综合，这些方法对设计师来讲早已熟悉了。

第10页：正常使用与强度极限状态

LRFDiswritteninaformthatpromptsthedesignerstoconsiderserviceabilityandstrengthlimitstatessystematically,soastructurewillhavehighperformancethroughoutits50ormoreyearsofservicelife.Highperformancemeansfewproblemsduringlowlife-cyclecost.LRFD

法可以以一种形式给出，它促使设计师系统地考虑正常使用和强度极限状态，因此，结构经过50年或更多年的使用期后仍性能良好。性能良好意味着较低的生命周期成本内出现的问题较少。

第11页：LRFD基本方程

In LRFD, each member and connection must satisfy thefollowing equation for each limit state:I Q i ≤R nWhere= Load factorQ = Load effect= Resistance factorR n =Nominalresistance在LRFD

法中，对于每个极限状态，每个构件和连接必须满足下面的等式：这里，是荷载系数；是荷载效应；是抗力系数；是标定的抗力。

第12页：各类荷载的系数差异

Different load factors are applied to different types of loads.For example, a smaller load factor is used for dead loads,because we can estimate these loads with better accuracy,while the load factor for live loads is larger, because of theuncertainties involved in determining the future changes in liveloads.The connections are designed stronger than themembers to reflect the lessons learned from structuralperformance and failures. This uniformity cannot be obtainedwith ASD using the same factor of safety for all types of loads,members, andconnections.

不同的荷载类型采用不同的荷载系数。

例如，对于恒载采用较小的荷载系数，因为我们能够较精确地估计出这些荷载，而对于活载采用较大的荷载系数，因为在确定活载将来的变化时存在不确定性。连接的设计强于构件以反应出从结构性能及破坏中学到的知识。这个统一性并不能够从ASD法中通过对所有类型的荷载、构件和连接采用相同的安全系数获得。

第13页：安全系数的工程判断

If the factor of safety too low, the likelihood of failure will behigh and hence the structure will be unacceptable; if the factoris too large, the structure will be wasteful of materials andperhaps unsuitable for its function (for instance, it may be tooheavy).Because of these complexities, good engineeringjudgment is required when establishing factors of safety. Theyare usually determined by groups of experienced engineerswho write thecodesand specifications used by otherdesigners.

如果安全系数太低，失效的可能性将很高，因此，这样的结构将是不能接受的；如果系数过大，结构将浪费材料，而且可能不适合它的功能（例如，它可能过重）。

由于这些复杂性，建立安全系数时需要良好的工程判断，它们通常是由经验丰富的编写规范的工程师决定的，而这些规范是设计师在设计过程中使用的。

第14页：Section B 地震作用

Section B EarthquakeEarthquakesare vibratory phenomena associated withshock loading on the earth’s crust, while these shock loads canresult from a number of causes, one of the primary reasons isthe suddenslippagethat frequently occurs between adjacentcrust plates that make up the earth’s surface.

地震是一种与地壳上震动荷载有关的震动现象，这些震动荷载的产生有许多原因，主要的原因之一是构成地表的相邻板块之间突然的滑动。

第15页：地震的发生深度

Mostearthquakesoccurwithintheupper15milesoftheearth’ssurface.Rutearthquakescananddooccuratalldepthstoabout450miles.Theirnumberdecreasesasthedepthincrease.Atabout460milesoneearthquakeoccursonlyeveryfewyears.Nearthesurface,earthquakesmayrunashighas100inamonth,buttheyearlyaveragedoesnotverymuch.

大多数地震都是发生再地表15英里范围内。

但是地震也可以发生在450英里的深度。地震发生的数量随着深度的增加而降低。在大约460英里处，每几年才会发生一次地震。接近地表处，一个月内，地震可以高达100次，但是年平均次数并不多。

第16页：重大震害案例

Examples of such disastrous earthquakes are the 1999Izmir,Turkeyearthquake; the 1999 Jiji, Taiwan ChinaEarthquake; the 1995 Henshin Japan Earthquake; the 1994Northridge, Califormia U. S. Earthquake; the 1976 Tangshan,China Earthquake; and many others.

损失惨重的地震如1999年土耳其伊兹密特地震；1999年中国台湾集集地震；1995年日本神户地震；1994年美国加利福尼亚北岭地震；1976年中国唐山地震及许多其它地震。

第17页：中国的地震活动

China is one of the most seismically active regions in theworld. There have been about 300earthquakes with magnitudesgreater than six in the continent of China since 1900 and sevenof these have had magnitudes greater than eight. The largestearthquakes in China generally occur in one of four zones

中国是世界上地震运动最活跃的地区之一。1900年至今，中国大陆大约有300次震级超过六级的地震，其中有七次地震震级超过八级。中国最大的地震一般发生于四个地区之一：

第18页：中国四大地震区

the Himalayan zone;2)the central Asia zone, extending northeast fromPamir, through Altai in western Mongolia to Baikal;3)the north-south zone,extending along the eastern margin of the Qinhai-Tibet Plateau;4)the northChina plain zone, which includes the Fenwei zone, the Hebei Plain and theTanlu zone, along the Pacific Ocean.

1）喜马拉雅山地区；2）中亚地区，从帕米尔地区向东北延伸，通过蒙古西部的阿尔泰山到贝加尔湖；3）南北地区，沿青藏高原的东边延伸；4）中国北部平原地区，包括沿太平洋的汾渭地区、河北平原和郯庐地区。

第19页：震害程度的影响因素

The extent of the disaster in an earthquake depends onmany factors. If you carefully build a toy house with anErector set, it will still stand to matter how much you shakethe table. But if you build a toy house with a pack of cards, aslight shake of the table will make it fall.An earthquake inAgadir, Morocco, was no strong enough to be recordedon distant instruments, but it completely destroyed the city.

地震中灾难的程度取决于许多因素。

如果你用安装设备仔细地建一个玩具房子，无论你怎么摇晃桌子，它也不会倒塌，但是如果你用纸片建一个玩具房子，轻轻要晃桌子它就会倒塌。摩洛哥阿佳迪尔的一次地震不够强，在远程仪器上没有记录下来，但是它完全破坏了这座城市。

第20页：建筑质量与震害减轻

Many stronger earthquakes have done comparatively littledamage. If a building is well constructed and build on solidground, it will resist on earthquake. Most deaths in earthquakeshave been due to faulty building construction or poor buildingsites.A third and very serious factor ispanic.When people rushinto narrow streets, more deaths will result.

许多强震的破坏较小。

如果建筑物很好地建造基础坚实，它就能够抵抗地震。大多数地震中的死亡是由于建筑物建造错误或建筑物的位置不好。第三个因素也是最严重的因素就是恐慌，当人们冲向狭窄的街道时，就会导致更多的死亡。

第21页：国际专家援助

TheUnitedNationshasplayedanimportantpartinreducingthedamagedonebyearthquakes.Ithassentateamofexpertstoallcountriesknowtobeaffectedbyearthquakes.Workingwithlocalgeologistsandengineers,theexpertshavestudiedthenatureofgroundandthetypeofmostpracticalbuildingcodeforthelocalarea.Iffollowed,thesesuggestionswillmakedisastrousearthquakesalmostathingofthepast.

英国在减小由地震产生的破坏方面起着重要的作用，英国把一支专家队伍送到了受地震影响的所有国家。

专家们与当地的地质学家和工程师一起工作，研究了土壤的性质以及大多数当地实际采用的建筑规范类型。如果继续下去，这些建议将会使灾难性的地震几乎成为过去。

第22页：海啸的成因

Thereisontypeofearthquakedisastersthatlittlecanbealoneabout.Thisisthedisastercausedbyseismicseawaves,ortsunamis.Incertainarea,earthquakestakeplacebeneaththesea.Thesesubmarineearthquakessometimesgiverisetoseismicseawaves.

有一种类型的地震灾难人们能够做的很少，这就是由地震的海浪引起的灾难，或海啸。

在某个区域，地震发生在海里，海里的地震有时会引起地震的海浪。

第23页：港湾波与水墙

The waves are not noticeable out at sea because of their long wave length.But when they roll into harbors, they pile up into walls of water 6 to 60 feethigh. The Japanese call them “tsunamis”, meaning “harbor wave”, becausethey reach asizableheight only in harbors.

这些浪由于波长较长在海里没有被注意到，但是当它们滚动到港湾时，就会堆积成6到60英尺高的水墙。

因为它们只在港湾处达到相当大的高度，所以日本人把它们称为“海啸”，意思是“港湾波”。

第24页：海啸预警系统

Tsunamistravelfairlyslowly,atspeedupto500milesanhour.Anearthquakewarningsystemisinusetowarnallshoreslikelytobereachedbywaves.Butthisonlyenablespeopletoleavethethreatenedshoresforhigherground.Thereisnowaytostoptheoncomingwave.

海啸推进的速度相当慢，每小时500英里。

地震警告系统用于警告所有海浪可能到达的海港。但是这仅仅能够使人们离开受到威胁的海港到高一点的地面上，没有办法阻止即将来临的海浪。

第25页：地震工程的技术挑战

In spite of the great progress obtained in the field ofearthquakes engineering during the past fifty years, recentdestructive earthquakes occurred around the world revealedthat the existing knowledge and techniques are still notsufficient to achieve safety against earthquakes at an effectivecost.

尽管过去五十年在地震工程领域取得了巨大进步，近来发生在世界范围的破坏性地震仍然表明现有知识和技术还不足以实现合理成本下的地震安全。

第26页：地震研究的重要地位

It is believed that among all natural hazards earthquakes are still number onedisaster for which in-depth research, particularly for those devastatingearthquakes, the basic research on earthquake engineering is still in need toexpand our knowledge and strengthen our defenses.

我们相信在所有自然灾害中，地震仍然是需要深入研究的头号灾难，特别是那些破坏性地震，仍需要通过地震工程的基础研究扩充我们的知识并加强我们的防御能力。

第27页：遥感与新技术应用

In recognition of the recent rapid advancement oftechnologies related to earthquake engineering, high-speeddevelopment of satellite remote sensing technology has playedsignificant roles in reducing various kinds of natural disasters, itcan be used in rapid assessing the seismic damage for effectivepost quake emergency action and in monitoring crustalmovement for better understanding of seismic risk.

近来与地震工程相关的技术得到快速发展。

卫星遥感技术的快速发展对减轻各种自然灾害起到了重要作用，它可以用来快速评估地震损害以采取有效的震后应急行动，还可以用于检测地壳运动从而更好地了解地震风险。

第28页：数字减轻灾害系统

The Digital Disaster Reduction System（数字减轻灾害系）would be a specially designed system to study the virtualseismic damages that may happen to real structures during realearthquakes.It is a virtual reality computer system designed tosimulate the occurrence and propagation of disaster and wholeprocess of damages caused by natural disasters.

数字减轻灾害系统是一个专门为研究虚拟地震损害而设计的系统，这种虚拟的地震损害在真实的地震到来时可能发生在实际结构上。

设计这个系统是为了模拟灾害的发生和传播以及由自然灾害引起的损害的整个过程。

第29页：系统的应用价值

The Digital Disaster Reduction System could be applied as a powerful tool notonly for seismic disasters study but also for other natural disaster research.

数字减轻灾害系统作为一个强有力的工具，不仅能够用于地震灾害的研究而且能够用于其它自然灾害的研究。

第30页：练习一 填空题

ExercisesⅠ. Fill in the blanks with the information given in the text.In order to find the most ______ structural system underthe given conditions, designers should be able to think in an______ way, concentrating on the ______ between spatialforms and ______ systems, and ignoring trivial details. Onthe other hand, designers should also be able to distinguishthe details which must be considered before the ______ ofthe whole system can be well understood.suitableoverallrelationshipstructuralproperties

第31页：结构材料与体系发展

Translate the following passages into ChineseWithin the last few years, research on building materialssuch as reinforced concrete and structural steel have madegreat strides and opened horizons for more efficient use ofthese materials.The structural engineers and architects alsohave met the challenge to find efficient and economical newstructural systems for various ranges and heights of buildingsgoing all the way to well over 100 stories.

过去几年中，对诸如钢筋混凝土和结构钢这样的建筑材料的研究取得了巨大进步，对于这些材料的有效利用也拓宽了视野。

结构工程师和建筑师也遇到了挑战就是要找到有效而经济的新的结构形式用于不同的建筑范围和高度甚至是对于超过100层的建筑物。

第32页：荷载的定义与方向

Section C LoadActionandPropagation（荷载作用和传递）Loads are forces acting on a structure. These loads aregenerated either directly by the forces of nature or by manhimself. Their way through the structural system to thefoundation is either vertical, such as dead, live, snow; orhorizontal, such as earthquake, wind. A force has bothmagnitude and direction.The magnitude is specified by thevalue of the force, and direction is specified by the line ofaction and the sense of the force.

荷载是作用在结构上的一些力，这些荷载可以是力直接作用，也可以是人为施加。

它们通过结构体系作用于基础的方式可以是垂直的如恒载、活载、雪；也可以是水平的，如地震荷载、风荷载。力有大小和方向。大小是通过力的值确定的，方向是由力的作用线和力的指向确定的。

第33页：静力荷载与动力荷载

Loads can be classified into two categories: static and dynamic. Staticloads are permanent and dynamic loads are always temporary. Dead loadsmay be defined as the static forces that are the weights of load-column,beam, floor,partitioning wall(隔墙),cladding wall(填充墙), etc.Theseloads are inside the building, other loads from inside the building areimposed by the live loads, such as people, librarybookshelves, furniture,hospital beds, industrial equipment, etc.These loads are variable, andalmost impossible to predict in static action. Their values take the form ofstatically equivalent loads. Loads from outside the building stem from theeffects of natural environment on the building.

荷载可以分为两类：静力荷载和动力荷载。

静力荷载是永久的，动力荷载总是临时的。恒载是柱、梁、楼板、隔墙、填充墙等自重的静力荷载.这些荷载是来自建筑物的内部，来自建筑物内部的其它荷载是由活荷载施加的，如人，图书馆书架，家具，医院的床，工业设备等。这些荷载是变化的，以静态作用来预测它们几乎是不可能的，它们的值要采用静力等效的形式来确定。来自建筑物外部的荷载产生于建筑物上自然环境的影响。

第34页：雪荷载与风荷载

These consist of snow, wind and earthquake loads. Thesnow loads acting on the roof cause the roofdeflect([di'flekt]v.挠曲，下垂),eventually collapse.Wind pressure values aregiven as functions of maximum annual mean wind velocities.The wind behavior and wind loading are studied throughwind tunnel test. Because of the nature of wind and the lackof better information，wind loads are considered to bestatically applied to the structure.Earthquake motions areapplied at the base of building from the ground below andare considered to be random-type loading. The earthquakeloads need not be considered if the building is not inearthquake zone.

这些荷载包括：雪载、风荷载和地震荷载。

雪载作用于屋面，引起屋面挠曲，甚至倒塌。风压力值按照每年平均风速最大值的作用给出。风的性能和风荷载是通过风洞试验研究的。由于风的性质以及缺乏较好的资料，风荷载作用于建筑物底部的地震力来自地面以都是按静力荷载施加到结构上的。下，它们是随机的荷载。如果建筑物不在地震区，就不需要考虑地震荷载。

第35页：荷载向基础的传递

All these loads, whatever from inside or outside the building,depend largely on the location of the building, have to be takenby the structural system from all points and manners ofapplication and transferred to the foundations.

所有这些荷载，不管是来自建筑物内部还是外部，极大地取决于建筑物的位置，这些荷载由结构体系从各个点以各种作用方式传递到基础。

第36页：传力机理与设计评价

It is clear that a properappreciation([əpri:∫i'ei∫ən]n.评价，鉴赏)of the behavior of a structural system, so essential to its properdesign, requires a correct understanding of the mechanismsand methods of load propagation,such as tension,compression, bending, shear, and torsion, for simple systemsand an additional elementary knowledge of at least deflectionsfor somewhat more complex systems. Tension is one of themost elementary mechanisms and most efficient way by whichload propagation takes place.

很清楚，恰当评价一个结构体系的性能对于它的合理设计是极其重要的，这就需要正确理解荷载传递的机理和方法。

例如对于简单的体系，应当了解拉伸、压缩、弯曲、剪切和扭转的知识；对于更复杂的体系，至少还应当知道关于挠度的基本知识。拉伸是荷载传递最基本的机理也是最有效的方法之一。

第37页：受拉与受压构件

In asuspension bridge, tension schemes generally require stiffeningbeams or trusses to avoid undesirable changes ingeometryunder movingor varying loads.Compression is the next most efficient method for carryingloads. The member must be designed to avoidbuckling(['bʌkliŋ]n.弯曲，屈曲，翘曲), either by making the member stocky or by adding supplementarybracing.Compression members weakendrastically(['dræstikəli] adv.彻底地，激烈地)when loads are not applied along the member axis, so moving,variable, and unbalanced loads must be carefully considered. Compressionoften exists incolumn(['kɔləm]n.柱). Through the mechanism ofcompression, the loads reach the foundation and hence the soil .

在悬索桥中，受拉设计一般需要提高梁或桁架的刚度以避免在移动荷载或变化荷载作用下几何形状发生变化。

压缩是另一个承担荷载最有效的方法之一，构件可以通过设计成短粗杆或增加辅助支撑以避免构件当构件承受的荷载没有沿构件的轴线方向作用时，构件会急剧削屈曲。弱，因此必须仔细考虑移动荷载、变化荷载及不平衡荷载。压缩经常存在于柱中，通过受压的机理，荷载能够到达基础从而到达土壤。

第38页：弯矩、剪力与扭矩

In structural member, such as beam, when the loads act vertically to thebeam[bi:m]n.梁, they are transmitted to the support by bending momentand shear force. The bending or flexure is resisted by one side of themember acting in tension while the other side acts in compression.Torsionis another of the methods by which load can be propagated toward thesupports. Consider a tube subjected to a torque at the free end, the tube isclamped at another end. Under the action of the torque, the tube twist,transferring the torque along its length until it reaches the support.Torsioncreates a shear stress in material of the tube.This is because every sectionof the tube attempts to shear, in a circular manner across the force of everyadjoining section.

在结构构件如梁中，当荷载垂直作用于梁上，它们由弯矩和剪力来传递。

弯矩是由受拉一侧来抵抗的而另一侧是受压的。扭矩是荷载传递的另外一种方法，考虑一端固定，另一自由端承受扭矩的一根管子，在扭矩的作用下管子扭曲，并把扭矩沿着它的长度方向传递到支撑端，扭这是由于管子的每个截面都试图在每个相邻矩在管子材料里产生剪应力。截面之间沿圆周方向剪切。

第39页：叠加原理与平衡条件

In statics, the total moments, shears, and otherstresses([stres]n.应力)caused by a group of loads are equal to the sum of the separate loads ifthe materials are in the elastic stage.When the structure is in equilibrium, itmust satisfy three conditions according tothe law of equilibrium(平衡原理).(1) The sum of the horizontal forces must equal zero. (2) The sum of thevertical forces must equal zero.(3) The sum of the moments about threerectangular coordinateaxes must equal zero. If theresultantforce andmoment were not zero, the structure would move under the action of theforce and rotate under the action of the moment.

• (1) The sum of the horizontal forces must equal zero.
• (2) The sum of thevertical forces must equal zero.
• (3) The sum of the moments about threerectangular coordinateaxes must equal zero. If theresultantforce andmoment were not zero, the structure would move under the action of theforce and rotate under the action of the moment.

根据平衡原理，当结构处于平衡状态时，必须满足三个条件，（1）水平方向力的（3）关于三个直角坐标轴和必须为零。（2）垂直方向力的和必须为零.的力矩的和必须为零。如果合力和力矩和不为零，结构在力的作用下会发生移动，在力矩的作用下会发生转动。

第40页：静定与超静定结构

Although not all structural systems can be analyzed by theuse of static alone, some can be solved easily.Staticdeterminacyis not unique to the structural system, in general,the same structure can also bestatically indeterminate.Understanding of load acting and propagation is important foran engineer to analyze structure，verbalize(['və:bəlaiz]v.用词语表达)structural system, thereby design and construct structure.

尽管并非所有结构只使用静力学原理来分析，但是一些结构使用静力学原理还是很容易解决的。

对于结构体系静定结构并不是唯一的，一般来讲，相同的结构也可以是超静定的。对于荷载作用及其传递的理解对于工程师分析结构，用词语表达结构体系从而进行结构的设计和施工是很重要的。