554-556 Third Avenue NY, New York

1. 554-556 Third Avenue NY, New York Michelle L. Mentzer Structural Option

2. Outline • Building Information • Structural Background • Problem Statement • Proposal • Structural Design • Architecture • Construction Management • Conclusions

3. Design Team • Owner • Maidman Development • Architect • H. Thomas O’Hara Architects • Structural Engineer • DeSimone Consulting Engineers • CM • BrawnMade Construction • Tishman Staff • MEP Engineer • MGJ Associates

4. Location 37th Street and Third Avenue Midtown Manhattan

5. Building Information • 30 Stories • 120,000 sq. ft. • 3600 sq. ft. Footprint • Residential occupancy • Ground floor • Retail space • Residential lobby • Fifth floor • Fitness room • Living units Ground Floor Fifth Floor

6. Building Information • Residential occupancy • Floors 2-24 • Marriott ExecuStay Suites • Floors 25-30 • Double height condominiums Floor 8-24 Floor 25-30

7. Structural Background Gravity System • Flat plate concrete construction • Floors 6-30 cantilever over buildings on 2 sides • Flat plate supports cladding load at cantilevers • Column walks shift loads toward building interior • Post-tensioning in slabs and columns near walks • Mat Foundation

8. Structural Background Column Walk • Column 12 on floor 5 • Column 18 on floor 8 • Resembles a wall between levels

9. Structural Background Lateral System • Wind loads govern for design loads • Shear wall core • Relatively uniform throughout building • Link beams connect walls above door openings • Extends above main roof to enclose penthouse

10. Problem Statement • Architectural style limited by thin cantilever slabs that cannot support heavy cladding • ADOSS model proved slabs would fail with heavy cladding load • Metal panels are the only option

11. Proposal • Develop an additional support system capable of carrying excess cladding loads • Steel trusses at roof level • Tension members hanging from trusses carry loads • Change façade through architectural precast panels and roof trusses • Determine impact these changes have on construction schedule, site layout and cost

12. Structural Design Truss Design • Braced frames replace shear walls above roof • System modeled in RISA • Applicable load cases considered • Continuous top & bottom chords • Pins at all other locations • Fixed supports at columns and shear walls

13. Structural Design Supporting Columns • Located wherever a truss joint coincides with a column/shear wall • Connections not necessarily centered on column

14. Structural Design Truss and Braced Frame Member Sizes • Maximum consistency • Lightest weight sections where possible • All wide flange shapes W14x90 W21x83 W14x211

15. Structural Design Truss Connections • Heavy bracing type connections at truss joints • Base plate and anchor bolts connect bottom chord to columns or shear walls

16. Structural Design Tension Members • W14x22, W14x34, W14x68 • Largest members at top • Reduce size as allowable • Hanger connection • Tension splices where necessary

17. Structural Design Slabs • No gravity load transferred from cladding to slabs • Cladding directly supported by columns • Angles welded to column flanges and bolted to panels • Lateral ties from panels to slab • Transfer wind forces to rigid diaphragm

18. Structural Design Column Walk • Added compression in column creates more tension in slab near column 18 on level 8 • Initially gravity load is fully vertical • As core reinforcement in column slants, gravity force creates horizontal component at slab level • Horizontal tension at level 8 is resisted by post-tensioning • One additional 1 3/8 “ Dywidag in level 8 slab • Original design calls for 5 Dywidags

19. Structural Design Column Capacities • Column capacities checked at critical locations using PCA Column • All support columns checked for gravity loads and moments from eccentricity • Dimensions and reinforcement increase in some areas • Exterior columns not supporting truss also checked • Supporting extra loads directly from cladding • Sufficient as designed to carry cladding loads

20. Structural Design Tension in Columns • Created by moment from cantilevered truss • Resisted by reinforcement in concrete

21. Structural Design Shear in Columns • Lateral loads from trusses and braced frames transferred directly to columns at roof level • Rigid diaphragm redistributes load at floor thirty • Where columns are in tension, shear reinforcement takes full shear load • Several columns require additional shear reinforcement at roof level

22. Structural Design Adjusted Column Sizes

23. Structural Design Overturning Moments • 0.9D+1.6W load case critical • Overturning caused by combination of wind and truss forces • Building overturning resisted by self weight and foundation • Safety factor (critical case)=2.5 • Moments cause tension and compression in opposite flanges of shear wall core • Spreadsheets used to check reinforcement for tension and compression in shear walls • Sufficient as designed to resist tension and compression loads

24. Architecture Cladding • Precast architectural panels • Architectural Precast Association • Acid-etched medium with yellow pigment • Red and beige tones blend with surroundings • Hint of yellow sets it apart and ties in idea of light associated with the name “Aurora”

25. Architecture Truss Design • Similar truss idea used in IBM Building, Baltimore, MD • Shape of trusses emphasizes cantilevers • Maximum symmetry possible • Add interest and detract from tall slender penthouse • Visible from street level

26. Architecture Column Dimensions Changes • West window shifts • No other substantial changes to layout necessary

27. Architecture Before After

28. Construction Management Sequencing • Finish pouring concrete before erecting steel • Enclosures cannot begin until after steel work is complete • Crane only needed for one task at a time

29. Construction Management • Tower crane capacity = 8 tons • Maximum member weight = 5 tons • Maximum panel weight = 7.5 tons • Street parking behind crane Site Logistics

30. Construction Management Schedule Impact • Durations from MC2 • Steel adds approx. 1.5 months to schedule • Panels take about the same amount of time to hang • Overall extension of schedule = 1.5 months

31. Construction Management Cost • Initial overall cost • R.S. Means = $18.2 million • Structural steel • MC2 =$220,000 • Panels (MC2) • Metal panels = $960,000 • Architectural precast panels = $2,200,000 • Proposal adds $1.5 million or 8.6% of initial cost

32. Conclusions • Trusses add architectural interest and allow use of a heavier cladding system • No substantial interruptions to interior layout • $1.5 million cost increase • 1.5 month schedule increase

33. Conclusions Recommendation • Revenue from architectural enhancements will not likely offset added costs and schedule delays • Use original metal panel cladding system

34. Acknowledgements DeSimone Consulting Engineers Penn State AE Faculty AE Class of 2003 My Family

35. Questions