Nijad Rudy Boukhalilstructural optionspring05

Presentation outlineProject backgroundExisting conditions Problem statementProposed solutionFloor systemLateral systemvibrationConstruction managementRecommendationsAcknowledgementsquestions

Project backgroundLocationon the corner of Bellevue Way 5 stories 3 above ground2 level parking39,000 square foot Rectangular shape 131x147Many openingsProject cost = $14 million

Project background

The museum has:

four classrooms for its Museum Schoolthree interactive Explore Galleriesa 90-seat auditoriuma multimedia librarya Museum storea small sidewalk caf2 story atriumOutdoor terraces

Project backgroundProject team

general contractor: Sellen construction Co. mechanical design/build contractor: Mckinstry Co.design architect: Steven Holl architects Associate Architect: Sclater Partners Architectsstructural engineer: Skiling Ward Magnusson barkshire, inc

Project backgroundArchitectural layout3 galleries 3 light qualities3 actions - see/explore/make (art, science, technology)3 main levels3 circulation directions

Existing conditionsFloor system

Composite steel deck3.5 concrete normal weight concretecompression strength fc = 4000 psi3 metal deckshear studs

AdvantagesGood with Long spanefficient and economicGood strength to weight ratioSmaller foundation needed

DisadvantagesCrane demandingDifficult coordinationvibration

Existing conditionsLateral system

Shear walls10 Cast-in-place#5 reinforcing barsbearing walls along perimeter and core around openings and the atrium. Advantages:The cast in place system: structure that is free of joints.achieve a continuous appearance of the applied finishes. provide the architect with the desired architectural finishShear walls

Existing conditionsSeismic Load Calculations (ASCE 7-02)AssumptionsOccupancy Category:IIISeismic Use Group:IISite Class:D

Seismic response coefficient: R=6

Problem statementSeismic hazard effect:Half of the states109 million people 4.3 million businesses

More frequent vibration key issue for a museum

Original systemFloor system: Composite floorLightweight system more subjected to vibration

Lateral system: Shear wallsGood choice against earthquakesEarthquake Cost damage:Direct cost: $1 billion/year indirect business losses: $2 billion/year

Proposed solutionsfloor system:

How vibrations dies outStiff diaphragm share the earthquake forces

Joist system spacing 2ft o.c (for vibration)

Advantages of joistLighter Weight reduce sizes of beams, columnsVarious sizes ~ Good for long spansLowers the overall cost of the project

Construction SpeededEach joist is a complete and independent unit.Allows field work to progress efficiently.

Proposed solutions

Lateral system

types of Lateral SystemsBracingMoment Frame

Why choose brace framesHave same advantagesused where shear walls are impractical.

Advantages of Braced Frames:High Strength and StiffnessMinimizes DeflectionsUses less MaterialCost Effective ~ Efficient and EconomicalStrong visual elementspeedy erection for faster return. More flexible to future changes than shear walls

Proposed solutionDifferent types of bracingsSingle Diagonals has to resist tension and compression caused by sideways forces in both directions on a frame.

Cross Bracing only need to resist tensionone brace is in tension for the sideways force in one direction on the frame, the other brace is in tension when the force is reversed. This is the most widely used type of bracing system.

Proposed solutionAdvantagesAllows for windows in walls, and other open spacesDisadvantagesLarge deflections

Larger Members

Cost increase

Why moment frames ok

Obstructions rejectedeliminates space limitations of solid shear walls braced frames. Moment frame:

floor systemJoist system using Vulcraft:Spacing = 2 o.c.Supports unchanged slab:3,5 concrete3 deck

Typical bay:

floor systemStress analysis The areas to be concerned about were around the elevator core and the openings

floor systemMoment diagram analysis

floor systemEncountered problem

A suspended stairway transports the visitor to the third floor along the north wall over head

floor systemSize up the beamThe right side beam of the staircase is required to be a W 40 X 183. The columns at the left support of the beam are a W 14X145, and the column at the right support is a W10X45 as shown in the figure below.Analysis in Etabs of the W 40 X 183:Deflection governedThe beam is spanning 60 feet, and with the shear walls gone, a W beam less than a W 40 X 183 will deflect more that L/480 = 1.5

Lateral systemChanges:

Core around elevatorShear walls braced framesAdd columns to replace shear wallsNeed moment frames around openings

Lateral systemCore:Braces: W12x96

Lateral systemNew columns in floor plan:

Lateral systemBracingWest facade

Lateral systemBracingSouth facade

Lateral systemBracingEast facade

Lateral systemType of moment connection:SidePlate Ideally suited against seismic

Up to 25% Reduction in Lateral Frame Tonnage

Up to 50%-65% Reduction in Field Welding Man-Hours

Lateral systemMoment connection distribution

Lateral systemETABS was used to design the lateral force resisting system of the buildingIBC 2000 earthquake pressureASCE 7-98 wind pressure.Check:DeflectionDrift controls

Lateral system Lateral drift

VibrationFloor vibrationHuman activities: walking Room: north gallery on 3rd floorVibration expectation: small to nonexistentUse design guide 11 from AISC

Goal: to understand which system is more adequate for vibration compare existing/new system

VibrationExisting systemComposite steel deck

VibrationModified systemJoist floor system

Both systems have the approximately the same percentage of the acceleration of gravity and are satisfactory to damp vibration while walking in the North gallery of the BAM.

Cost comparison

Cost comparisonRedesigned floor system

Cost comparisonExisting lateral system

Cost comparison

RecommendationsDisadvantages of Braced Frames: Obstructive interfere with architectural requirementsLow Ductility Disadvantages of Moment Frames: Expensive Lots of material plus labor-intensive connections.Low Stiffness

Floor system = joistLess expensiveVibration checked

decision

lateral system = shear wallsLess expensiveDrift checked

acknowledgmentsThank youMy AE classmatesMy friendsmy familyfriends & familyfacultyProf. Parfitt Dr. Boothby Dr. Hanagan Dr. MemariMr. Tim Bade Mr Ziad Jamaleddine Steven holl architects

Questions?