BalsaBridgeCompetitionOverviewTheBalsaBridgeCompetitionoffersparticipatingteamstheopportunitytodemonstrateknowledgeofstructuraldesignprinciplesintheconstructionofathree-dimensionalbalsabridgestructure.Studentswilldesignandbuildabridgestructureusingspecifiedbalsawood.Thestructurewillbeweighedandjudgedandthenloadeduntilfailure.ObjectiveTheobjectiveofthiscompetitionistodesignandbuilda3-Dbridgestructureconformingtospecificcriteria.Themodelwillbetestedviaaloadingplatformplacedonthedeckofthestructure.Theloadwillbeincreasedwithrespecttotimeuntilfailureoccursbythefractureofamemberorajoint.Pointswillbeawardedforthestrengthtoweightratioofthebridgeandforthequalityofthetechnicalpaper.EligibilityEachteammayconsistofuptofour(4)students,one(1)ofwhommaybeagraduatestudent.Eachteamwillhaveone(1)captain,whowillsubmitthebridgeandahardcopyofthetechnicalreportduringregistration.One(1)structureperuniversitywillbeallowed.Allcompetingbridgesmustmeetalldesignspecifications.Failuretomeetanyrequirementwillresultinadeductionofpointsordisqualification.SubmittalsAlltechnicalpapersandbridgestructuresmustbesubmittedwiththeregistrationoftheteamcaptainuponarrivalattheconference.Eachbridgemusthavethenameoftheuniversityprintedinpermanentblackinkalongthelengthofone(1)ormoreofthebridgemembers.MaterialsWoodOnlybalsamembersofA,B,orCgraintypesmaybeused.Drydensityofbalsamembersmaynotexceed15lbs/ft3.Nospecializedortreatedbalsawood,basswood,orothertypesofwoodareallowed.Thenominalcrosssectionofallmembersmustbe.25inx.25in±.025in.Structuralmembersmaynotextendbelowtheplanecreatedbytheloadingdeck.
GlueOnlyone(1)typeofglueperstructureisallowed.Thewoodglueusedmustbefromthefollowinglist:
o Elmer’sWoodGlueo TitebondOriginalI,II,orIIIWoodGlueso WeldbondGlueo GorillaWoodGlue
DesignParameters
o Nopaint,stain,orcoatingofbalsamembersisallowed.o Laminatingofmembersisnotallowed.o Gussetplatesareallowedtosupportjoints.o Excessiveglueassistingstrengthofbridgewillresultinpointdeduction.Alljoints
shouldbecleanofexcessglue.o Lengthofbridgeshallbestrictlybetween26”and30”.o Heightofbridgeshallnotexceed8”.o Widthofbridgeshallnotexceed6”.o A2x4blockofwood,(actualdimensions1.5”x3.5”)simulatingavehiclemustbe
abletopassthroughthebridgeacrossthebridgespan.Nodeckingsurfaceisrequired,simplyanopeningthatcanaccommodatetheblock,approximatelylevelwithspansupports.
o Thedeckofthebridgeisunderstoodtobeaplanarsurfacespanningtheentirelength.
o Numberofstructuralmembersintersectingatasinglejointmaynotexceedsix.o Allbridgestructuresmustaccommodatea1”x1”x9”barplaced
perpendicularlyonthecenterofthedeckspacefromwhichtheloadwillbeapplied.(SeeFigures1&2).
TestingTheorderoftestingwillbedeterminedbythejudges,andteamswillbenotifiedinadvanceoftestingorder.Theteamcaptainmustbepresentatthetimeoftesting;otherteammembersarenotrequiredbutmayattend.Theteamcaptainwillplacethebridgeacrossthe24”supportspan.Afterthebridgeisplacedonthespan,noadjustmentsmaybemadetothestructure.
Loadingwillbesuspendedbelowthebridge.Thesupportmechanismconsistsofanironbarwithdimensions1”x1”x9”thatwillbeplacedperpendicularlytothedecksurface.Chainswillbehungfromtheendsofthisbar.Abucketwillbesuspendedfromthechains.Bridgeswillbeloadeduntilfailurebyfillingthebucketwithsand.Therateofloadingwillbereducedatvisibledeformationorcrackingtoensuretheweightatcatastrophicfailureisexactlyrecorded.
JudgingTherewillbeaminimumofthree(3)judgesforthecompetition.Itwillbethejudges’dutyandresponsibilitytoevaluatetheteamsfairlyandconsistently.TheteamswillbeevaluatedbasedonthecriteriaoutlinedintheScoringsectionincludedbelow.Thejudges’rulingwillbefinalforallcompetitors.TechnicalPaperThetechnicalpapershallbe750-1000wordsinlengthandconsistof:
1. Introductiona. NameofUniversityb. Namesofteammembersc. Captainnameandcontactinformation
2. Documentationa. Allmaterialsusedforconstructionofbridge,including:
i. Balsawood,includingacountofallvertical,horizontal,andinclinemembers
ii. Thenameofadhesiveproductusedb. Purchaselocationofallmaterials,includingphotocopiesofreceiptsof
purchase.
3. Methodologya. Explanationofdesignprocessincluding:
i. Anyandallassumptionsmadeii. Alternatedesignsconsiderediii. Constructionprocess
b. Estimatedloadcapacitywithallcalculationsc. Hypothesisandtheoriessupportingchosendesign.
4. Figuresa. FullplanviewCADfigurewithallanglesanddimensionstoscale.All
anglesanddimensionsshouldbewithinareasonabletoleranceoftheactualstructure.FailuretomeettoleranceshallresultinpointdeductionfromtheTechnicalPaperScore.
b. Additionalscaledanddimensionviewsmaybesubmittedatthediscretionoftheteam.Pointswillbeawardedforclarityanddetail.
c. AllCADfiguresshallbesubmittedwiththetechnicalreporton8.5”x11”sheets.
ScoringScoresforthetechnicalpaperwillbebaseduponorganization,completeness,accuracy,andadherencetoallrequirements.Ascoringsummaryisprovidedonthefollowingpage.Aloadingcapacityscorewillbedeterminedbytheultimateloadcapacity(lbs)dividedbytheweight(grams)totwodecimalplaces.Thisvaluewillbemultipliedbyten(10)todeterminethetotalpointsawarded.Theteamwiththehighesttotalscorewillwinthecompetition,receivingthefullseven(7)pointsintheoverallscorebreakdownfortheconference.Intheeventofatie,thejudgesshallchoosethewinnerbasedonqualityofconstructionandaesthetics,whichshallbejudgedbeforeloadingbegins.
ScoringSummarySheet
ASCEStudentOrganization:_______________________________________
TechnicalPaperScoringRubric Score1.Introduction /152.Documentation /20
3.Methodology /40
4.Figures /25TechnicalPaperSub-Total /100
Infractions Deduction1.GlueViolation -10/instance2.MemberViolation -30/instance3.JointViolation -20/instance
4.BridgeViolatesLengthorHeightDimension Disqualification
5.LoadingDeckFailstoMeetSpecification Disqualification
StructuralDesignScore Sub-Total[LoadCapacity/TotalMass]x10-Deductions
TechnicalPaperSub-Total /100StructuralDesignSub-Total OverallScore