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StructureofBulidingsAbuildingiscloselyboundupwithpeople,foritprovidespeoplewiththenecessaryspacetoworkandlivein.Asclassifiedbytheiruse,buildingsaremainlyoftwotypes:industrialbuildingsandcivilbuildings.Industrialbuildingsareusedbyvariousfactoriesorindustrialproductionwhilecivilbuildingsarethosethatareusedbypeoplefordwelling,employment,educationandothersocialactivities.Theconstructionofindustrialbuildingsisthesameasthatofcivilbuildings.However,industrialandcivilbuildingsdifferinthematerialused,andinthestructureformsorsystemstheyareused.Consideringonlytheengineeringessentials,thestructureofabuildingcanbedifinedastheassemblageofthosepartswhichexistforthepurposeofmaintainingshapeandstability.Isprimypurposeistoresistanyloadsappliedtothebuildingandtotransmitthosetotheground.Intermsofarchitecture,thestructueofabuildingisanddosemuchmorethanthat.Itisaninseparablepartofthebuildingformtovaryingdegreesisageneratorofthatform.Usedskillfully,thebuildingstructurecanestablishorreinforceordersandrhythmsamongthearchitecturevolumesandplanes.Itcanbevisuallydominantorrecessive.Itcandevelopharmoniesorconflicts.Itcanbebothconfiningandemincipating.And,unfortunatelyinsomecases,itcannotbeingored.Itisphysical.Thestructuremustalsobeengineeredtomaintainthearchitectureform.Theprinciplesandtoolsofphysicsteandmathematicsprovidethebasisfordifferentiatingbetweenrationalandinrationalformsintermsofconstruction.Artistscansometimesgenerateshapesthatobviateanyconsiderationofscience,butarchitectscannot.Thereareatleastthreeitemsthatmustbepresentinthestructureofabuilding:stabily,strengthandstiffness,economy.Takingthefirstofthethreerequiements,itisobviousthatstabilityisneededtomaintainshape.Anunstablebuildingstructureimpliesunbalancedforcesoralackofequilibriumandaconsequentaccelerationofthestructureoritspieces.Therequirementofstrengthmeansthatthematerialsselectedtoresistthestressesgeneratedbytheloadsandshapesofthestructure(s)mustbeadequate.Indeed,a“factorofsafety”isusuallyprovidedsothatundertheanticipatedloads,agivenmaterialisnotstressedtoalevelevenclosetoitsrupturepoint.Thematerialpropertycalledstiffnessisconsideredwiththerequirementofstrength.Stiffnessisdifferentformstrengthinthatitdirectlyinvolveshowmuchastructurestrainsordeflectsunderload.Amaterialthatisverystrongbutlackinginstiffnesswilldeformtoomuchtobeofvalueinresistingtheforcesapplied.Economyofabuildingstructurereferstomorethanjustthecostofthematerialused.Constructioneconomyisacomplicatedsubjectinvovlingrawmaterials,fabrication,erection,andmaintenance.Designandconstructionlaborcostsandthecostsofenergyconsumptionmoney(interest)areconsumptionmustbeconsiedered.Speedofconstructionandthecostofmoney(interest)arealsofactors.Inmostdesignsituations,morethanonestructuralmaterialrequiresconsideration.Completivealternativesalmostalwaysexist,andthechoiceisseldomobvious.Apartformthesethreeprimaryrequirements,severalotherfactorsareworthyofemphasis.First,thestructureorsuctructuralsystemmustrelatetothebuilding’sfunction.Itshouldnotbeinconflictintermsofform.Forexample,alinearfunctiondemandsalinearstructure,andthereforeitwouldbeimpropertoroofabowlingalleywithadome.Similarly,atheatermusthavelarge,unobstructedspansbutafinerestaurantprobablyshouldnot.Statedsimply,thestructuremustbeappropriatetothefunctionitistoshelter.Second,thestructuremustbefire-resistant.Itisobviousthatthestructuralsystemmustbeabletomaintainitsintegrityatleastuntiltheoccupuantsaresafelyout.Buildingcodesspecifythenumberofhoursforwhichcertainpartsofabuildingmustresisttheheatwithoutcollapse.Thestructuralmaterialsusedforthoseelementsmustbeinherentlyfire-resistantorbeadequentlyprotectedbyfireproofingmaterials.Thedegreeoffireresistancetobeprovidedwilldependuponanumberofitems,includingtheuseandoccupancyloadofthespace,itsdimensions,andthelocationofthebuilding.Third,thestructureshouldintegratewellwiththebuilding’scirculationsystems.Itshouldnotbeinconflictwiththepipingsystemsforwaterandwaste,theductingsystemsforair,or(mostimportant)themovementofpeople.Itisobviousthatthevariousbuildingsystemsmustbecoordinatedasthedesignprogresses.Onecandesigninasequentialstep-by-stepmannerwithinanyonesystem,butthedesignofallofthemshouldmoveinaparallelmannertowardcompletion.Spatially,allthevariouspartsofabuildingareinterdependent.Fourth,thestructuremustbepsychologicallysafeaswellasphysicallysafe.Ahighriseframethatswaysconsiderablyinthewindmightnotactuallybedangerousbutmaymakethebuildinguninhabitablejustthesame.Ligheweightfloorsystemsthataretoo“bouncy”canmaketheusersveryuncomfortable.Largeglasswindows,uninterruptedbydividingmotions,canbuquitesafebutwillappearveryinsecuretotheoccupantstandingnexttoon40floorsabovethestreet.Sometimesthearchitectmustmakedeliberateattemptstoincreasetheapparentstrengthorsolidnessofthestructure.Thisapparentsafetymaybemoreimportantthanhonestlyexpressingthebuilding’sstructure,becausetheuntrainedviewercannotdistinguishbetweenrealandperceivedsafety.Thebuildingdesignerneedstounderstandthebehaviorofphysicalstructuresunderload.Anabilitytointuitor“feel”str