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FOUNDATIONSOFCIVILANDENVIRONMENTALENGINEERING
No.7
2006
SélimDATOUSSAID
*,GuyGUERLEMENT,ThierryDESCAMPS
DepartmentofCivilEngineeringandStructuralMechanics
FacultéPolytechniquedeMons,RueduJoncquois53,7000Mons,Belgium
APPLICATIONSOFEVOLUTIONARYSTRATEGIESIN
OPTIMALDESIGNOFMECHANICALSYSTEMS
Received:30June2006
Accepted:20September2006
Thispaperisconcernedwiththeoptimizationofstructuralsystems.Ononehand
itconcernsthekinematicordynamicbehaviourofmultibodysystems.Ontheotherhand
itconcernstheminimumweightdesingofframesaccordingtostaticanddynamiccon-
straints.Theauthorsfirstrecalltheclassicalformofanoptimizationproblem,whose
purposeistofindthesetofdesignvariableswhichminimizesagivenobjectivefunction
whileverifyingpotentialconstraints.Afterrecallingtheprincipaloptimizationtech-
niques,theevolutionarystrategiesarepresentedindetail.Theyareinspiredfromthe
naturalevolution:thegenesofindividualsmutatefromgenerationtogenerationandthe
survivingsarethosebeingthebestfittedtotheirenvironment.Theanalogywithan
optimizationproblemisquitestraightforward:asetofdesignvariablescanbeconsid-
eredasthegenesofanindividualandthevalueoftheobjectivefunctionforthissetof
designvariablesrepresentsthefitnessforsurvivalofthecorrespondingindividual.Prac-
tically,themutationisperformedbymodifyingthedesignvariablesofµparents,ac-
cordingtoanormaldistributionwithzeroasaverageandgivesrisetoλoffsprings
whosebestµindividualsformthenewparentpopulation.Thepapergivessomeindica-
tionsforthechoiceoftheprincipalparametersoroptionsandexplainshowtomanage
themutationinordertocontrolthespeedofconvergence.Theperformancesoftheevo-
lutionarystrategiesarethenillustratedbythreeexamples:thestructuraloptimizationof
atwo-storeysteelframe,thekinematicoptimizationofasuspensionandthedynamic
optimizationofthecomfortofarailwayvehicle.
Evolutionarystrategies,althoughslowerthanhill-climbingmethods,areaninter-
estingalternative.Theyindeedhaveseveraladvantages:theoptimizationengineremains
*Correspondingauthor.Tel.:32(0)65-37-45-23;fax:32(0)65-37-45-28.
E-mailaddress:selim.datoussaid@fpms.ac.be(S.Datoussaid)
©PublishingHouseofPoznanUniversityofTechnology,Poznań2006
ISSN1642-9303