303 Third St, 303 Third St, Cambridge, MACambridge, MA

Brian TuftsStructures Option

Advisor: Dr. Ali Memari4/14/08

Architecture OverviewArchitecture Overview• Urban setting near M.I.T.

• Must appeal to affluence• Technology area

• Contrast of materials • Terra-cotta • Metal paneling

• Creates it’s own world with U footprint and green space centrally located• 3 levels of parking below grade• Retail on the ground level• Apartments start on the ground floor

Building ProgrammingBuilding Programming• Total Building Area:

830,000 SF• Residential Area:

595,000 SF• Retail Area: 8,000 SF• Parking: 215,000 SF• North Building Area:

327,000 SF• North Building:

• 292 Units • 41 Studio 650 SF EA• 136 1 Bed 850 SF EA• 103 2 Bed 1200 SF EA• 12 3 Bed 1550 SF EA

Overview of Building SystemsOverview of Building Systems• Structural

• Composite steel framing• 3 ¼ LWC on 3” 16 ga composite metal floor deck

• Electrical• 2 primary power distribution boards• (2) 300 kVA transformers provide 120/208V to panels• Backup power via 750 kW generator

• Mechanical• 2 cooling towers each for north and south buildingtotaling ~150,000 CFM per building• 5 water cooled AC units service lobby and fitness areas• 14 rooftop air conditioning units service corridors• 4 boilers totaling 23,300 MBH

Thesis ObjectivesThesis Objectives• Evaluate an alternative floor framing system using open-web steel joists

• Compare seismic performance• Reduce lateral framing• Reduce gravity columns• Check vibration performance• Explore fireproofing issues• Compare cost savings

• Mechanical Breadth – Building Envelope Efficiency• Check envelope performance with Massachusetts Energy Code• Propose 2 pane window to increase envelope performance• Compare cost of two systems and energy performance

Massachusetts State Building Massachusetts State Building Code Sixth EditionCode Sixth Edition

Based on Building Officials and Code Administrators National Building Code – BOCA 1993

Key differences from ASCE 7◦ Wind – The reference wind velocity for each wind load zone

is the “fastest-mile” wind velocity, in miles per hour, at 30 feet about the ground Pv = 90 mph for Cambridge, MA Reference wind pressure for Exposure C = 31 psf Resulting story shear is less conservative than BOCA

◦ Seismic - Equivalent Lateral Frame Method – BOCA R = 5.0 for Concentrically Braced Frames R = 4.5 for Ordinary Moment Frames Effective peak acceleration: Av = Aa = 0.12g for all of

Massachusetts Ct = 0.20

Typical Composite Steel FramingTypical Composite Steel Framing

• Beam Spacing: 12.5’ (Typ) with 18’-1” span• Girders typically span 25’

Typical Bay FramingTypical Bay Framing

Typical Bay – Composite SteelTypical Bay – Steel Joists

Lateral Frames Along Line ELateral Frames Along Line E

Composite Steel Steel Joists

Lateral System & Gravity Column Lateral System & Gravity Column ComparisonComparison

Cost: $3500/Ton for steel and erection in Boston, MA

Typical Bay ComparisonTypical Bay Comparison

Ceiling SectionsCeiling Sections

FireproofingFireproofing

VibrationVibration• Analyzed the typical bay for walking excitation and a future office occupancy

• Typical joist is 12K1• Typical girder is VLH24

• Δj = 0.186 in• Δg = 0.266 in

• fn = 5.263 Hz• a0/g = 0.003 < 0.005

Depth Study SummaryDepth Study Summary• Open-web steel joists would save initial costs in column steel and lateral framing members.

• Steel joists are also cheaper to frame than composite steel framing.

• Vibration is not an issue for this application of steel joists as the typical bay is more than adequate for walking excitation.

• If the 12’ floor-floor height is adequate, alternate fireproofing detail would alleviate issues related to the application of cementitious fireproofing.

• Open-web steel joists are a viable alternate framing system for 303 Third Street.

Mechanical Breadth Study – Mechanical Breadth Study – Building EnvelopeBuilding Envelope

Typical Wall Sections

Wall U-ValuesWall U-Values

Calculated using the ASHRAE Handbook of Fundamentals

Energy Compliance CheckEnergy Compliance Check

Specified walls and ¼” clear float glass fail energy compliance check by 30%

Proposed Two Pane WindowProposed Two Pane Window• Increase building envelope efficiency by 14%

•Cost roughly $45/SF including framing and installation, compared to $35/SF for single pane windows

Image courtesy of http://www.energystar.gov

ConclusionsConclusions• Open-web steel joists are a viable alternative floor framing system

• Two pane glass may be necessary to meet minimum energy code and result in a 14% increase in envelope performance for 303 Third Street

• Increased envelope performance will help obtain LEED points under the Optimize Energy Performance section of the LEED Reference Guide

• A decrease in window area and an increase in wall insulation will increase envelope performance, but has architectural and apartment rent ability implications.

ThanksThanks• McNamara/Salvia Inc. Consulting Engineers - Boston, MA

• Mark Aho, P.E.• John Matuszewski, P.E.• Adam McCarthy, P.E.• Robert McNamara, P.E., S.E.• Joseph Salvia, P.E.

• William Waterston, AIA - Wiss, Janney, Elstner Associates, Inc. – Cambridge, MA• Hank Klein - Extell Development Company –Boston, MA• Andrew Copelotti - Equity Residential –Boston, MA• Mark Pasciuto - Bovis Lend Lease LMB, Inc.– Boston, MA• Woth Ngan - Bovis Lend Lease LMB, Inc.– Boston, MA• Martin Turnbull – AHA Consulting Engineers – Lexington, MA

•The AE Department

•Friends and Family who supported me while preparing this thesis

Questions?Questions?