1. TOWERS CRESCENT
BUILDING B
Mike Synnott
Structural

2. OVERVIEW Site Information Historical Breadth Existing Structure
Towers Crescent Building B
Mike Synnott
Structural Option
Advisor – Kevin Parfitt
OVERVIEW
Site Information
Historical Breadth
Existing Structure
Proposal
Design for Gravity
Design of Lateral Resistance
Cost Analysis
Conclusion

3. Site Information Towers Crescent Building B Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Site Information

4. Towers Crescent Building B Mike Synnott Structural Option
Advisor – Kevin Parfitt
Location: Vienna, Virginia
9 Stories
Height – 122’ 9”
Occupancy - Retail/Office
1 of 3 Buildings On Site
Red – Towers Crescent
Original building
Blue – Building B
Green – Building C
Buildings B & C Based off Original Building

5. History Breadth Towers Crescent Building B Mike Synnott
Structural Option
Advisor – Kevin Parfitt
History Breadth

6. Towers Crescent Building B Mike Synnott Structural Option
Advisor – Kevin Parfitt
Original Towers Crescent Building 
Original Site Plan to have 3 Identical Buildings
Total Square Footage – 450,000 sf/Building
New Design to Create 5 Smaller Buildings
Total Square Footage – 900,000 sf
2 of the 5 Buildings Built, 1 in Design, 2 in Planning
Design of Building B Based Off Original Building
Due To Architectural Importance, Height Of Building B Not Considered in Analysis

7. Philip Johnson Architect of Original Building
Towers Crescent Building B
Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Philip Johnson Architect of Original Building
Designer of Such Buildings as:
The Glass House – 1949
Crystal Cathedral – 1980
AT&T Headquarters – 1984
Transco Tower – 1983
Transco Tower
AT&T Headquarters
Crystal Cathedral
The Glass House

8. Existing Structure Towers Crescent Building B Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Existing Structure

9. Floor System: Towers Crescent Building B Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Floor System:
210’ x 110’ Footprint
2 Typical Bay:
40’ x 30’
30’ x 30’
Composite Steel Floor
2” Metal Deck
3 ¼” Slab
Shear Studs to Transfer Load

10. Lateral Resistance System
Towers Crescent Building B
Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Lateral Resistance System
Steel Braced Frames
4 Frames North/South Direction
2 Frames East/West Direction
Limits Drift to 1.5” < 3.68” Allowable Drift
North/South Frames
East /West Frames

11. Proposal Towers Crescent Building B Mike Synnott Structural Option
Advisor – Kevin Parfitt
Proposal

12. Design 2 Alternate Structures and compare to Existing Structure
Towers Crescent Building B
Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Design 2 Alternate Structures and compare to Existing Structure
First Alternate Structure:
Column Layout Same As Existing Structure
Two Way Concrete Flat Slab
Beams Spanning Between All Columns
Two Way Post Tensioning
Shear Walls

13. Second Alternate Structure: Addition Row of Columns
Towers Crescent Building B
Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Second Alternate Structure:
Addition Row of Columns
Two Way Concrete Flat Slab
Drop Panels
Shear Walls Resisting Lateral Loads

14. Design for Gravity Towers Crescent Building B Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Design for Gravity

15. First Alternate Structure
Towers Crescent Building B
Mike Synnott
Structural Option
Advisor – Kevin Parfitt
First Alternate Structure
Floor System
Typical Bays:
40’ x 30’
30’ x 30’
9”, Post Tensioned, Flat Slab
Interior Beams – 16” x 18”
Exterior Beams – 24” x 24”

16. Post Tensioning Longitudinal Tendons Lateral Tendons Spaced 10’ O.C.
Towers Crescent Building B
Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Post Tensioning
Lateral Tendons
Spaced 5’ O.C.
15 Strands Along Beams
2 Strands Between Beams
Profile Points:
At Ends "
At Mid-span - 3"
Longitudinal Tendons
Spaced 10’ O.C.
25 Strands For Most
27 For 40’ Spans
Profile Points:
At Ends - 21"
At Mid-span - 3.5"

17. Column Design Towers Crescent Building B Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Column Design

18. Second Alternate Structure
Towers Crescent Building B
Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Second Alternate Structure
Floor System
Typical Bay:
30’ x 27.5’
7” Flat Slab
7” Drop Panels

19. Column Design Towers Crescent Building B Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Column Design

20. Design of Lateral Resistance
Towers Crescent Building B
Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Design of Lateral Resistance

21. Both Alternate Structures
Towers Crescent Building B
Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Both Alternate Structures
Shear Walls Located Around All Openings in Slab
12” Thickness
Total Drift – 0.79” < 3.68” Allowable Drift
Deflection of North/South Facing Walls
Deflection of East/West Facing Walls

22. Cost Analysis Towers Crescent Building B Mike Synnott
Structural Option
Advisor – Kevin Parfitt
Cost Analysis

23. Towers Crescent Building B Mike Synnott Structural Option
Advisor – Kevin Parfitt
Construction Times
Existing Structure – 51 Days
Alternate 1 – 135 Days
Alternate 2 – 126 Days

24. Conclusion Towers Crescent Building B Mike Synnott Structural Option
Advisor – Kevin Parfitt
Conclusion

25. When Not Considering Height Changes:
Towers Crescent Building B
Mike Synnott
Structural Option
Advisor – Kevin Parfitt
When Not Considering Height Changes:
Not Considered due to Architectural Constraints
Existing Structure Most Efficient Design
Lowest Cost
Shortest Construction Time
Simple Design
When Considering Height Changes:
Ignoring Architectural Constraints
Second Alternate Structure Most Efficient
18” per floor saved - 13'-6" Total
Much Lower Overall Cost ~ $45 million vs. $48 million

26. Questions? Towers Crescent Building B Mike Synnott Structural Option
Advisor – Kevin Parfitt
Questions?

27. 1st Alternate Structure
2nd Alternate Structure