303 Third St, Cambridge, MA

1. 303 Third St, Cambridge, MA Brian Tufts Structures Option Advisor: Dr. Ali Memari 4/14/08

2. 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 Architecture Overview

3. 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 Building Programming

4. 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 building • totaling ~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 Overview of Building Systems

5. 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 Thesis Objectives

6. 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 Massachusetts State Building Code Sixth Edition

7. Typical Composite Steel Framing • Beam Spacing: 12.5’ (Typ) with 18’-1” span • Girders typically span 25’

8. Typical Bay – Steel Joists Typical Bay – Composite Steel Typical Bay Framing

9. Lateral Frames Along Line E Composite Steel Steel Joists

10. Lateral System & Gravity Column Comparison Cost: $3500/Ton for steel and erection in Boston, MA

11. Typical Bay Comparison

12. Ceiling Sections

13. Fireproofing

14. 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 Vibration

15. 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. Depth Study Summary

16. Mechanical Breadth Study – Building Envelope Typical Wall Sections

17. Wall U-Values Calculated using the ASHRAE Handbook of Fundamentals

18. Energy Compliance Check Specified walls and ¼” clear float glass fail energy compliance check by 30%

19. Increase building envelope efficiency by 14% • Cost roughly $45/SF including framing and installation, compared to $35/SF for single pane windows Proposed Two Pane Window Image courtesy of http://www.energystar.gov

20. 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. Conclusions

21. 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 Thanks

22. Questions?