Nijad Rudy BoukhalilNijad Rudy Boukhalilstructural optionstructural option

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Presentation outlinePresentation outline Project backgroundProject background Existing conditions Existing conditions Problem statementProblem statement Proposed solutionProposed solution Floor systemFloor system Lateral systemLateral system vibrationvibration Construction managementConstruction management RecommendationsRecommendations AcknowledgementsAcknowledgements questionsquestions

Project background Location

on the corner of Bellevue Way 5 stories

3 above ground 2 level parking

39,000 square foot Rectangular shape 131’x147’ Many openings Project cost = $14 million

Project background

The museum has:

four classrooms for its Museum School three interactive Explore Galleries a 90-seat auditorium a multimedia library a Museum store a small sidewalk café 2 story atrium Outdoor terraces

Project backgroundProject team general contractor:

Sellen construction Co. mechanical design/build contractor:

Mckinstry Co. design architect:

Steven Holl architects Associate Architect:

Sclater Partners Architects structural engineer:

Skiling Ward Magnusson barkshire, inc

Project backgroundArchitectural layout 3 galleries 3 light qualities 3 actions - see/explore/make (art, science, technology) 3 main levels 3 circulation directions

Existing conditionsExisting conditions

Floor systemFloor system

Composite steel deckComposite steel deck• 3.5” concrete 3.5” concrete

normal weight concretenormal weight concrete compression strength fc’ = 4000 psicompression strength fc’ = 4000 psi

• 3” metal deck3” metal deck• shear studsshear studs

AdvantagesAdvantages Good with Long spanGood with Long span efficient and economicefficient and economic Good strength to weight ratioGood strength to weight ratio Smaller foundation neededSmaller foundation needed

DisadvantagesDisadvantages Crane demandingCrane demanding Difficult coordinationDifficult coordination vibrationvibration

Existing conditionsExisting conditions

Lateral systemLateral system

Shear walls• 10” Cast-in-place• #5 reinforcing bars• bearing 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 finish

Shear walls

Existing conditionsExisting conditionsSeismic Load Calculations (ASCE 7-02)Seismic Load Calculations (ASCE 7-02) AssumptionsAssumptions

• Occupancy Category:Occupancy Category: IIIIII• Seismic Use Group:Seismic Use Group: IIII• Site Class:Site Class: DD

Seismic response coefficient: R=6Seismic response coefficient: R=6

Problem statementProblem statement Seismic hazard effect:Seismic hazard effect:

• Half of the statesHalf of the states• 109 million people 109 million people • 4.3 million businesses4.3 million businesses

More frequent vibration More frequent vibration key issue for a museum key issue for a museum

Original systemOriginal system Floor systemFloor system: Composite floor: Composite floor

• Lightweight system Lightweight system more subjected to vibration more subjected to vibration

Lateral systemLateral system: Shear walls: Shear walls• Good choice against earthquakesGood choice against earthquakes

Earthquake Cost damage:Earthquake Cost damage:• Direct cost: $1 billion/year Direct cost: $1 billion/year • indirect business losses: $2 indirect business losses: $2

billion/yearbillion/year

Proposed solutionsProposed solutions

floor system:floor system:

How vibrations dies outHow vibrations dies out Stiff diaphragm Stiff diaphragm

share the earthquake forces share the earthquake forces

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

Advantages of joistAdvantages of joist Lighter Weight Lighter Weight

reduce sizes of beams, columnsreduce sizes of beams, columns Various sizes ~ Good for long spansVarious sizes ~ Good for long spans Lowers the overall cost of the projectLowers the overall cost of the project

Construction SpeededConstruction Speeded Each joist is a complete and independent unit.Each joist is a complete and independent unit. Allows field work to progress efficiently.Allows field work to progress efficiently.

Proposed solutionsProposed solutions

Lateral systemLateral system

types of Lateral Systemstypes of Lateral Systems BracingBracing Moment FrameMoment Frame

Why choose brace framesWhy choose brace frames Have same advantagesHave same advantages used where shear walls are impractical. used where shear walls are impractical.

Advantages of Braced Frames:Advantages of Braced Frames: High Strength and StiffnessHigh Strength and Stiffness Minimizes DeflectionsMinimizes Deflections Uses less MaterialUses less Material Cost Effective ~ Efficient and EconomicalCost Effective ~ Efficient and Economical Strong visual elementStrong visual element speedy erection for faster return. speedy erection for faster return. More flexible to future changes than shear wallsMore flexible to future changes than shear walls

Proposed solutionProposed solution

Different types of bracingsDifferent types of bracings

Single DiagonalsSingle Diagonals

has to resist tension and has to resist tension and compression caused by sideways compression caused by sideways forces in both directions on a forces in both directions on a frame.frame.

Cross BracingCross Bracing

only need to resist tensiononly need to resist tension• one brace is in tension for the one brace is in tension for the

sideways force in one direction on sideways force in one direction on the frame, the frame,

• the other brace is in tension when the other brace is in tension when the force is reversed. the force is reversed.

This is the most widely used type This is the most widely used type of bracing system. of bracing system.

Proposed solutionProposed solution

AdvantagesAdvantages Allows for windows in walls, Allows for windows in walls,

and other open spacesand other open spaces

DisadvantagesDisadvantages Large deflectionsLarge deflections

Larger MembersLarger Members

Cost increaseCost increase

Why moment frames okWhy moment frames ok

•Obstructions rejectedObstructions rejected•eliminates space limitations of solid shear walls eliminates space limitations of solid shear walls braced frames. braced frames.

Moment frame:Moment frame:

floor system

Joist system using Vulcraft: Spacing = 2’ o.c. Supports unchanged slab:

3,5” concrete 3” deck

Typical bay:

floor system

Stress analysis The areas to be concerned about were around the elevator core

and the openings

floor system

Moment diagram analysis

floor system

Encountered problem

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

floor system Size up the beam

The 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 governed The 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 frames

•Add columns to replace shear walls•Need moment frames around openings

Lateral system•Core:

•Braces: W12x96

Lateral system

• New columns in floor plan:

Lateral system• Bracing

– West facade

Lateral system• Bracing

– South facade

Lateral system• Bracing

– East facade

Lateral system

Type 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 system

Moment connection distribution

Lateral system

• ETABS was used to design the lateral force resisting system of the building– IBC 2000 earthquake pressure– ASCE 7-98 wind pressure.

• Check:– Deflection– Drift controls

Lateral system

• Lateral drift

Level Height Disp Drift limit (H/400)

roof 60’ 0.72” 1.8” Pass

3rd 34’ 0.48” 1.02” Pass

2nd 18’ 0.15 0.54” Pass

Vibration

Floor vibration• Human activities: walking • Room: north gallery on 3rd floor• Vibration expectation: small to nonexistent• Use design guide 11 from AISC

Goal: to understand which system is more adequate for vibration

compare existing/new system

Vibration

Existing system• Composite steel deck

Vibration

Modified system• Joist 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 comparison•Redesigned floor system

Cost comparison

•Existing lateral system

Cost comparison

RecommendationsRecommendationsDisadvantages of Braced Frames: Disadvantages of Braced Frames: ObstructiveObstructive

interfere with architectural requirementsinterfere with architectural requirements Low DuctilityLow Ductility

Disadvantages of Moment Frames: Disadvantages of Moment Frames: ExpensiveExpensive

Lots of material plus labor-intensive connections.Lots of material plus labor-intensive connections. Low StiffnessLow Stiffness

Floor system = joistFloor system = joist Less expensiveLess expensive Vibration checkedVibration checked

decisiondecision

lateral system = shear lateral system = shear wallswalls

Less expensiveLess expensive Drift checkedDrift checked

acknowledgmentsacknowledgments

• Thank youThank you

My AE classmatesMy friendsmy family

friends & family

faculty

Prof. Parfitt ۰ Dr. Boothby Dr. Hanagan ۰ Dr. Memari

Mr. Tim Bade Mr Ziad Jamaleddine

Steven holl architects

Questions?Questions?