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Oregon State University. 2008 PEER Seismic Design Competition. Design Process: Criteria. To begin the design, look at how the project will be scored: Points can be won based on: Seismic Performance Rental Income Presentation/Poster Architecture/Workmanship - PowerPoint PPT Presentation


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Oregon State University2008 PEER Seismic Design Competition

Design Process: CriteriaTo begin the design, look at how the project will be scored:Points can be won based on:Seismic PerformanceRental IncomePresentation/PosterArchitecture/WorkmanshipFor the design of the structure, 3 categories count: IncomeBuilding CostPerformanceArchitectureRental IncomeThe first design criteria we addressed was to maximize the rental incomeTo do this-Maximize floor spaceMaximize number of floorsMaximize floor space on upper floorsThe first thing we designed was a 5 tall tower with 29 floorsBuilding CostDont bother minimizing this valueLarger footprints provide structural advantagesMore weight means more members and more strengthThe cheapest structure will not be the bestMaximizing Seismic PerformancePoints are earned by having the lowest possible roof acceleration and drift

Very rigid or very flexible buildings will have the smallest acceleration and drifts.Stiff BuildingWe decided that it would be best to go with a very rigid buildingThere is a trade off in using more materials:Higher rigidityHigher weightWeight of balsa wood will be small comparedto the applied loadsBetter to go with more woodAdding more members also adds connections and:StiffnessLoad pathsRedundancy

Additional Design MethodologyFrom past years, and common sense, simple, uniform designs will win:No re-entrant cornersNo twistingNo tapering at topAlso allows max rental incomeIrregularities cause torsion and stress concentrationsRectangles fail easily compared to trianglesUsing Diagonal members allowed us to:Maximize the number of connectionsIncrease number of load pathsDistribute the loadAdditional Design MethodologyMaximize dimensions of footprintLarger shear wallsLarger lever arm Increases cross section moment of inertia Section can carry larger loadsMinimize columnsSimply not necessary-saves on weightAdditional support for loadsPoints of loading require additional reinforcementDetermine which floors will hold the loads (1/8*h)Brace these laterally on the interiorIncreased cross bracing through walls at these points

AnalysisLooked up material properties:

Must appreciate the variability of woodRan SAP2000 using Time History and Response Spectrum analysis on several variationsAnalyzed rigid and flexible connections, used 80/20 weighted averageDoesnt make a big differenceAveraged the two analysesPicked the best overall design

Specific GravityStatic Bending Stress at Proportional LimitStatic Bending Modulus of RuptureStatic Bending Modulus of ElasticityCompression Parallel to grain stress at Proportional LimitCompression Parallel to grain Maximum CrushingCompression Parallel to Grain Modulus of ElasticityCompression Perpendicular to Grain TangentiallyCompression Perpendicular to Grain Loaded RadiallyShear Parallel to Grain TangentialShear Parallel to Grain RadialTension Perpendicular to Grain TangentialTension Perpendicular to Grain Radial0.087501250260,000370700210,0007542.5170147103680.109001500300,000525900300,0009654204178120770.1210501800327,0007501150420,000103782382271361040.1615002740580,00013301850660,000147923502881671200.1819803310650,00015401995810,0001601104143201741240.20------3560705,0001,7252435865,000187140448388231147Changes In DesignOur design looks like last years winner (OSU)Same methodology (Stiffness, simplicity are good)Good ideas last year, could use some improvementMore members near corners, and at load pointsFewer members elsewhere:Not necessarySaves self weightThis saves on weightDecrease the angle of incline on the cross members in all four wallsLateral support system changed to increase redundancy and the number of load paths

SummaryMostly an afterthought through the design processTurned out very prettyArchitectureOur design will:Maximize floor space and number of floorsBe very rigid, and structurally redundantBe as simple and uniform as possibleHave wide wallsHave increased support at load points

Performance PredictionBest guess or worst case estimates:Annual Income:$1,468,000Total Building Cost:$247,000Annual Seismic Cost:$159,000 Annual Building Revenue:$1,062,000

Thank You and ReferencesDr. Scott Ashford, CCE, OSUDr. Tom Miller, CCE, OSUTransportation Professors, CCE, OSUPacific Earthquake Engineering Research CenterLaura Elbert, Student, CCE, OSU

Material properties from:Dreisbach, John F. (1952) Balsa and Its Properties. Columbia, Connecticut: Columbia Graphs


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