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Nijad Rudy Boukhalil structural option spring’05

Nijad Rudy Boukhalil structural option spring’05. Presentation outline. Project background Existing conditions Problem statement Proposed solution Floor system Lateral system vibration Construction management Recommendations Acknowledgements questions. Project background. Location

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Nijad Rudy Boukhalil structural option spring’05

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  1. Nijad Rudy Boukhalilstructural optionspring’05

  2. Presentation outline • Project background • Existing conditions • Problem statement • Proposed solution • Floor system • Lateral system • vibration • Construction management • Recommendations • Acknowledgements • questions

  3. 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

  4. 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

  5. Project background Project 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

  6. Project background Architectural layout • 3 galleries • 3 light qualities • 3 actions - see/explore/make (art, science, technology) • 3 main levels • 3 circulation directions

  7. Floor system Composite steel deck 3.5” concrete normal weight concrete compression strength fc’ = 4000 psi 3” metal deck shear studs Advantages Good with Long span efficient and economic Good strength to weight ratio Smaller foundation needed Existing conditions Disadvantages • Crane demanding • Difficult coordination • vibration

  8. 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: • The cast in place system: structurethat is free of joints. • achieve a continuous appearance of the applied finishes.  provide thearchitect with the desired architectural finish Shear walls

  9. Existing conditions Seismic Load Calculations (ASCE 7-02) • Assumptions • Occupancy Category: III • Seismic Use Group: II • Site Class: D • Seismic response coefficient: R=6

  10. Problem statement • Seismic hazard effect: • Half of the states • 109 million people • 4.3 million businesses • More frequent vibration  key issue for a museum Original system • Floor system: Composite floor • Lightweight system  more subjected to vibration • Lateral system: Shear walls • Good choice against earthquakes • Earthquake Cost damage: • Direct cost: $1 billion/year • indirect business losses: $2 billion/year

  11. Proposed solutions floor system: How vibrations dies out • Stiff diaphragm  share the earthquake forces Joist system  spacing 2ft o.c (for vibration) Advantages of joist • Lighter Weight • reduce sizes of beams, columns • Various sizes ~ Good for long spans • Lowers the overall cost of the project • Construction Speeded • Each joist is a complete and independent unit. • Allows field work to progress efficiently.

  12. Proposed solutions Lateral system types of Lateral Systems • Bracing • Moment Frame Why choose brace frames • Have same advantages • used where shear walls are impractical. Advantages of Braced Frames: • 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

  13. Proposed solution Different types of bracings • Single Diagonals • has to resist tension and compression caused by sideways forces in both directions on a frame. • Cross Bracing • 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. • This is the most widely used type of bracing system.

  14. Advantages Allows for windows in walls, and other open spaces Disadvantages Large deflections Larger Members Cost increase Proposed solution Moment frame: • Why moment frames ok • Obstructions rejected • eliminates space limitations of solid shear walls braced frames.

  15. floor system Joist system using Vulcraft: • Spacing = 2’ o.c. • Supports unchanged slab: • 3,5” concrete • 3” deck Typical bay:

  16. floor system • Stress analysis • The areas to be concerned about were around the elevator core and the openings

  17. floor system • Moment diagram analysis

  18. Encountered problem floor system • A suspended stairway transports the visitor to the third floor along the north wall over head

  19. 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”

  20. Lateral system • Changes: • Core around elevator • Shear walls  braced frames • Add columns to replace shear walls • Need moment frames around openings

  21. Lateral system • Core: • Braces: W12x96

  22. Lateral system • New columns in floor plan:

  23. Lateral system • Bracing • West facade

  24. Lateral system • Bracing • South facade

  25. Lateral system • Bracing • East facade

  26. 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

  27. Lateral system Moment connection distribution

  28. 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

  29. Lateral system • Lateral drift

  30. 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

  31. Vibration Existing system • Composite steel deck

  32. 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.

  33. Cost comparison

  34. Cost comparison • Redesigned floor system

  35. Cost comparison • Existing lateral system

  36. Cost comparison

  37. Recommendations Disadvantages of Braced Frames: • Obstructiveinterfere with architectural requirements • Low Ductility Disadvantages of Moment Frames: • ExpensiveLots of material plus labor-intensive connections. • Low Stiffness decision • Floor system = joist • Less expensive • Vibration checked • lateral system = shear walls • Less expensive • Drift checked

  38. acknowledgments • Thank you faculty Steven holl architects Prof. Parfitt ۰ Dr. Boothby Dr. Hanagan ۰ Dr. Memari Mr. Tim Bade Mr Ziad Jamaleddine friends & family My AE classmates My friends my family

  39. Questions?

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