Third Avenue NY, New York Michelle L. Mentzer Structural Option

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Outline Building Information Structural Background Problem Statement Proposal Structural Design Architecture Construction Management Conclusions

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Location 37 th Street and Third Avenue Midtown Manhattan

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Building Information 30 Stories 120,000 sq. ft sq. ft. Footprint Residential occupancy  Ground floor Retail space Residential lobby  Fifth floor Fitness room Living units Ground Floor Fifth Floor

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Building Information Residential occupancy  Floors 2-24 Marriott ExecuStay Suites  Floors Double height condominiums Floor 8-24 Floor 25-30

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Structural Background Column Walk Column 12 on floor 5 Column 18 on floor 8 Resembles a wall between levels

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Structural Design Supporting Columns Located wherever a truss joint coincides with a column/shear wall Connections not necessarily centered on column

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Structural Design Truss and Braced Frame Member Sizes Maximum consistency Lightest weight sections where possible All wide flange shapes W21x83 W14x211 W14x90

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Structural Design Truss Connections Heavy bracing type connections at truss joints Base plate and anchor bolts connect bottom chord to columns or shear walls

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Structural Design Tension Members W14x22, W14x34, W14x68  Largest members at top  Reduce size as allowable Hanger connection Tension splices where necessary

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Structural Design Tension in Columns Created by moment from cantilevered truss Resisted by reinforcement in concrete

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Structural Design Adjusted Column Sizes

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Architecture 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” Cladding

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Architecture Column Dimensions Changes West window shifts No other substantial changes to layout necessary

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Architecture BeforeAfter

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Construction Management Tower crane capacity = 8 tons Maximum member weight = 5 tons Maximum panel weight = 7.5 tons Street parking behind crane Site Logistics

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Construction Management Schedule Impact Durations from MC 2 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Construction Management Cost Initial overall cost  R.S. Means = $18.2 million Structural steel  MC 2 =$220,000 Panels (MC 2 )  Metal panels = $960,000  Architectural precast panels = $2,200,000 Proposal adds $1.5 million or 8.6% of initial cost

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis 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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Conclusions Recommendation Revenue from architectural enhancements will not likely offset added costs and schedule delays Use original metal panel cladding system

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

Third Avenue – The Aurora Michelle L. Mentzer – Structural Emphasis Questions