Nijad Rudy Boukhalil
structural option
spring’05
Presentation outline
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Project background
Existing conditions
Problem statement
Proposed solution
Floor system
Lateral system
vibration
Construction management
Recommendations
Acknowledgements
questions
Project background
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Location
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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:
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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 background
Project team
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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 background
Architectural layout
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3
3
3
3
3
galleries
light qualities
actions - see/explore/make (art, science, technology)
main levels
circulation directions
Existing conditions
Floor system
Composite steel deck
• 3.5” concrete
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normal weight concrete
compression strength fc’ = 4000 psi
• 3” metal deck
• shear studs
Advantages
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Disadvantages
Good with Long span
 Crane demanding
efficient and economic
 Difficult coordination
Good strength to weight ratio
 vibration
Smaller foundation needed
Existing conditions
Lateral system
Shear walls
• 10” Cast-in-place
• #5 reinforcing bars
• bearing walls along perimeter and core
• around openings and the atrium.
Advantages:
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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 conditions
Seismic Load Calculations (ASCE 7-02)
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Assumptions
• Occupancy Category:
III
• Seismic Use Group:
II
• Site Class:
D
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Seismic response coefficient: R=6
Problem statement
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Seismic hazard effect:
• Half of the states
• 109 million people
• 4.3 million businesses
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Earthquake Cost damage:
• Direct cost: $1 billion/year
• indirect business losses: $2
billion/year
More frequent vibration  key issue for a museum
Original system
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Floor system: Composite floor
• Lightweight system  more subjected to vibration
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Lateral system: Shear walls
• Good choice against earthquakes
Proposed solutions
floor system:
How vibrations dies out
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Stiff diaphragm
 share the earthquake forces
Joist system
 spacing 2ft o.c (for vibration)
Advantages of joist
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Lighter Weight
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reduce sizes of beams, columns
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Various sizes ~ Good for long spans
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Lowers the overall cost of the project
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Construction Speeded
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Each joist is a complete and independent unit.
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Allows field work to progress efficiently.
Proposed solutions
Lateral system
types of Lateral Systems
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Bracing
Moment Frame
Why choose brace frames
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Have same advantages
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used where shear walls are impractical.
Advantages of Braced Frames:
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High Strength and Stiffness
Minimizes Deflections
Uses less Material
Cost Effective ~ Efficient and Economical
Strong visual element
speedy erection for faster return.
More flexible to future changes than shear walls
Proposed solution
Different types of bracings
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Single Diagonals
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has to resist tension and
compression caused by sideways
forces in both directions on a
frame.
Cross Bracing
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only need to resist tension
• one 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.
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This is the most widely used type
of bracing system.
Proposed solution
Moment frame:
Why moment frames ok
•Obstructions rejected
•eliminates space limitations of solid shear walls
braced frames.
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Advantages
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Allows for windows in walls,
and other open spaces
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Disadvantages
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Large deflections
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Larger Members
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Cost increase
floor system
Joist system using Vulcraft:
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Spacing = 2’ o.c.
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Supports unchanged slab:
 3,5” concrete
 3” deck
Typical bay:
floor system
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Stress analysis
 The areas to be concerned about were around the elevator core
and the openings
floor system
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Moment diagram analysis
floor system
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Encountered problem
A suspended stairway transports the visitor to
the third floor along the north wall over head
floor system
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Size up the beam
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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:
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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 system
Changes:
•Core around elevator
Shear walls  braced frames
•Add columns to replace shear walls
•Need moment frames around openings
Lateral system
•Core:
•Braces: W12x96
Lateral system
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New columns in floor plan:
Lateral system
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Bracing
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West facade
Lateral system
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Bracing
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South facade
Lateral system
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Bracing
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East facade
Lateral system
Type of moment connection:
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SidePlate™
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Ideally suited against seismic
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Up to 25% Reduction in Lateral Frame Tonnage
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Up to 50%-65% Reduction in
Field Welding Man-Hours
Lateral system
Moment connection
distribution
Lateral system
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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
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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
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Composite steel deck
Vibration
Modified system
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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
Recommendations
Disadvantages of Braced Frames:
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Obstructive
interfere with architectural requirements
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Low Ductility
Disadvantages of Moment Frames:
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Expensive
Lots of material plus labor-intensive connections.
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Low Stiffness
decision
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Floor system = joist
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Less expensive
Vibration checked
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lateral system = shear walls
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Less expensive
Drift checked
acknowledgments
• Thank you
faculty
Steven holl architects
Prof. Parfitt ۰ Dr. Boothby
Dr. Hanagan ۰ Dr. Memari
friends & family
My AE classmates
My friends
my family
Mr. Tim Bade
Mr Ziad Jamaleddine
Questions?