Brian Tufts - Structural

303 Third Street, Cambridge, MA

Note: While great efforts have been taken to provide accurate and complete information on the pages of CPEP, please be aware that the information contained herewith is considered a work‐in‐progress for this thesis project. Modifications and changes related to the original building designs and construction methodologies for this senior thesis project are solely the interpretation of Brian Tufts. Changes and discrepancies in no way imply that the original design contained errors or was flawed. Differing assumptions, code references, requirements, and methodologies have been incorporated into this thesis project; therefore, investigation results may vary from the original design.

Building Statistics

Part 1

General Building Data

Building name: 303 Third Street
Location and site: Located in Cambridge, MA, the 3.3 acre site is bounded by Third Street to the east, Potter Street to the south, Fifth Street to the west, and Linsky Way to the north.
Building Occupant Name: A partnership between Extell Development Corporation and Equity Residential
Occupancy or function types: Mixed-use facility primarily consisting of residential units with some retail.
Size (total square feet): 485,227 SF of rentable residential space with 7,500 SF of retail space
Number of stories above grade / total levels: Between 5 and 8 above grade levels with 2 below grade parking levels

Primary project team:

Owner: Extell Development Corporation and Equity Residential
Architect: Cetra/Ruddy Inc
Landscape Architect: Copley Wolff Design Group
General Contractor and Construction Manager: Bovis Lend Lease
Structural Engineer: McNamara/Salvia, Inc
MEP Engineer: MGJ Associates
Lighting Consultant: Cosentini Lighting Design
Civil Engineer: Tetra Tech Rizzo
Geotechnical Engineer: McPhail Associates, Inc
Waterproofing Consultant: Wiss, Janney, Elstner Associates, Inc
Fire and Code Consultant: Hughes Associates, Inc

Dates of construction: July 2006 – October 2008
Actual cost information: Total Project Development Cost of $246 million
Project delivery method: Design-bid-build with a GMP contract

Architecture

Architecture (design and functional components)

330 Third Street is a large mixed-use development situated in urban Cambridge, MA. The site is located a short distance from the Massachusetts Institute of Technology and other prominent Cambridge landmarks. As such, 303 Third Street aims to create a green outdoor space within the site and a modern, elegant façade to attract busy city professionals.

303 Third occupies a 3.3 acre site and consists of two large building (North and South) segments forming a U, with a green space filling the center. Parking is available via two below grade parking levels. The design seeks to maximize rentable space while maintaining a comfortable living environment for its occupants.

Major national model code: Massachusetts State Building Code – 6th Edition which is modeled after BOCA 1999
Zoning: 303 Third Street is located in Cambridge Zone PUD-KS which is designed for mixed use – office, residential, and retail spaces of at least 40,000 SF.
History of the site: An existing 1-2 story brick building is located at the northeast corner of the site and an existing 1-story brick building fronts onto Potter Street to the south. The southwest and southeast corners of the site are occupied by electrical and steam easements, respectively. The portions of the site not occupied by the existing buildings are typically blanketed by bituminous concrete pavement. The existing ground surface across the subject site is relatively flat.

Building envelope:

Floor-to-ceiling heights are typically 10’-0” and the exterior is sheathed primarily in a curtain wall with a terra cotta veneer. This gives the building a regal appearance which is quite breath-taking when compared to the metal sheathing on other curtain walls. The intent of the design is to encourage busy city professionals to settle down near Kendall Square and MIT, just a short walk away from the subway.

By varying the heights of the various buildings, 303 Third Street creates an active roofline giving different angles for the occupants and spectators. Buildings vary in number of floors from 5 to 8 above grade floors. The roof system consists of roof girders supporting 3 in x 18 gage metal roof deck with a concrete topping slab and waterproofing membrane.

Part 2 Building Systems:

Mechanical:

Two cooling towers in each building (north and south) total ~150,000 per building provide the buildings with cool air. Along with the cooling tower, five water cooled AC units are employed in the pool area, lobby, and fitness spaces of the building to remove heat and environmental control. There are also fourteen rooftop air conditioning units servicing the corridors and home offices. The building is heated by four boilers located in the north and south penthouse mechanical areas totaling 23,300 MBH.

Lighting

The residential condominium units are provided with two pole mounted 208V lights with 175W metal halide lamps in the kitchen. Other lighting throughout the building is typically surface mounted 120V fluorescent fixtures with two T5 lamps.

Electrical

Two primary power distribution boards service the two buildings (north and south) located below grade on level P1 in the north and south buildings. From there, the power is stepped down to 120/208V 3 phase, 4 wire via two 300 kVA transformers to feed the panel boards servicing the spaces. Backup power is provided by a 750 kW 120/208V 3 phase, 4 wire generator.

Structural

The foundation of the building is supported by interior and exterior piers as well as belled caissons with depths typically around 20’. Parking level 2 consists of 5” slab on grade concrete with 6X6 – W2.9 x W2.9 WWF. The interior wide flange columns of the building bear on square spread footings and are typically W12s. Typical floors are composite construction with 4 ½” of reinforced concrete on a 3” 18 ga metal floor deck. Wide flange beams typically span 25’ with 8’ spacing. Beams range in size from W14 to W18 and have a typical camber of up to 1”. Girders are also wide flanges sized up to W24 with cambers over 1”. The structure is laterally supported by braced frames with HSS bracing elements as well as by moment frames in the E-W direction.

Construction

Bovis Lend Lease is acting as the CM and GC in this venture under a guaranteed maximum price contract. Construction is expected to go from July 2006 to October 2008.

Fire Protection

Spray-on fire proofing is to meet the following specifications: 2 hours for floors, 2 hours for columns, 1 hour for the roof, and 2 hours for the metal deck. A fire alarm system is also in place with automatic sprinklers.

Transportation

There are five elevators located in the north building all located in the east and west ends of the building. The south building has six elevators with four in the east and west ends and two elevators located in the mid-section of the building. The central-most elevator in the south building is for service and staff.

Telecommunications

Tenants will install their own individual communications systems.