Jessica Lucas

Mechanical Option
731 Lexington Avenue
New York, NY

This is a student-generated Capstone Project e-Portfolio (CPEP) produced in conjunction with the AE Senior Thesis e-Studio.

The building statistics assignment provided below describes the Bloomberg Tower located at 731 Lexington Avenue in NYC. The focus of this thesis investigation changed from the Bloomberg Tower to the Hearst Tower at the start of Technical Assignment #2.


BUILDING NAME: The Bloomberg Tower or 731 Lexington Avenue

LOCATION AND SITE: 731 Lexington Avenue, New York, NY 10022

BUILDING OCCUPANT NAME: Bloomberg LP, anchor tenant

OCCUPANCY OR FUNCTION TYPES: Multi-use Building comprised of office space,
retail space, and residential luxury condos

SIZE (TOTAL SF): 1.4 million SF

NUMBER OF STORIES: 55 stories with 3 levels below grade


• Owner: Vornado Realty Trust
• Design Architect: Cesar Pelli and Associates
• Architect of Record: Schuman, Lichtenstein, Claman, & Efron Architects
• Construction Manager: Bovis Lend Lease
• MEP Engineers: Flack+Kurtz
• Structural Engineers: The Thornton-Tomasetti Group
• Consulting Engineer: Rosenwasser Grossman Inc.
• Structural Steel Contractor: ADF Group

DATES OF CONSTRUCTION: construction started June 2002 with shell and core
completion in 2004, substantial completion in Spring 2005

COST: Overall: $630 Million





731 Lexington Avenue, also known as the Bloomberg Tower, is a mixed-use building that has captured the Project of the Year award for that category in 2004. Extending from East 58th to 59th street and from 3rd Avenue to Lexington Avenue, the building features a slender high-rise tower and a ten story building connected on the 4th, 5th, and 6th floors. The building also features a six story, glass walled atrium creating an oval shaped public plaza with a passenger drop off area. The 55-story tower rises on the Lexington Avenue side and provides views of Central Park and Midtown for the 105 luxury condos on the upper floors. In addition to the residential spaces, 900,000 SF of office space will be home to Bloomberg LP Headquarters and additional rentable space; and 160,000 SF of space will include retailers such as Home Depot, H&M, bank branches, and a restaurant.

The building façade consists of a glass and metal curtain wall system beginning on the third floor with stainless steel finishes through the tower. The building is topped off with a crown that glows softly. The curtain wall features fins that extend 13”off of the window face. The two storefront stories include stainless steel and glass and incorporate stainless steel columns. The Lexington Place drive through also features stainless steel and glass features with skylights and a standing seam metal roof.


Commercial zone. Building site is the former site of Alexander’s Department Store, which was demolished in 1998 to allow for construction of this multi-use building.


New York City Building Code



One of the major challenges faced during construction was a redesign of the overall site plan. The original design called for a residential/commercial tower with a hotel occupying floors 10-22 on the Third Avenue side of the site. The Lexington Avenue side
of the site would consist of an 8 story podium. Upon a request by the anchor tenant, Bloomberg LP, for additional office space, the design plan was completely changed moving the tower to the Lexington Avenue side and eliminating the hotel plans. This request came after 160,000 cu. yds. of rock had been excavated.

Aside from the initial design issues, the site itself posed construction constraints. Located in Midtown Manhattan, the site is bounded by two main approaches to the Queensboro Bridge; therefore closure of these streets was not permitted by the city.

Bovis Lend Lease, the construction manager, had to keep the project on track by dividing the project into multiple phases, with each phase being placed on a schedule and agreed to by all major contractors. This schedule was written into the steel contract forcing the steel contractor to start fabrication for early phases while design of other phases was still in progress.


With a redesign occurring after excavation, the structural team had to redesign the foundation to support the new loads. In addition to changes made to the floor plans, the structural system of the tower was changed from being a structural steel system. The new system is comprised of structural steel framing with concrete on metal deck from Lower Level Two through the 30th floor with a complete break occurring at 30th floor, at this level the system transitions to a reinforced concrete structure. One of the biggest challenges of using this system was creating a continuous load path between the steel and concrete portions of the building. Since the concrete columns did not align with the steel columns below, the 30th floor acted as a transfer floor where encased trusses were used to redistribute loads from the upper concrete superstructure to the steel superstructure below.

The office floor structural system is typically comprised of W18 floor beams, 8 core columns, and exterior columns placed away from corners to maximize office views. The residential portion of the tower features a concrete shear wall core with a flat plate concrete floor system. The flat plate slab is 9” thick and spans from 15’-23’. Columns supporting the residential floors are typically 18”x24”.

Since the upper floors of the Bloomberg Tower are luxury condos, serviceability was taken into consideration during design. The design team determined that additional damping would be needed to balance wind induced building acceleration. After determining that 600 tons of mass would be needed for damping, The Thornton-Tomasetti Group worked with Motioneering to select a stacked double mass passive tuned mass damper (TMD) system as opposed to a conventional pendulum damper system. With the amount of damping needed, a pendulum system would have required a 60’ length, while the double-stacked system only requires a 25’ TMD room height. With this stacked system, a 220 ton secondary damper rests on unstable pin-pin posts and is stabilized by a 380 ton primary mass through axial struts.


Electrical service is distributed to 731 Lexington through a 460/265V, 3-phase, 4-wire system. The system utilizes four existing Consolidated Edison transformer vaults with a two vault addition. The service consists of 5-4000A take-offs routed from expanded network protector space in Lower Level One to switchgear rooms on Lower Level Two. These take-offs terminate in service switchboards with ground fault monitoring. The electrical distribution system is also equipped with two levels of transient voltage surge protection.

Each office floor contains an electrical closet with a vertical bus duct riser, a 460/265V panel, a 208/120V panel, and a K-13 rated step down transformer. General use receptacles are provided with 120V single phase service, while specific use receptacles are supplied with 120V single phase, 208V single phase, or 208V three phase power. 265V single phase power is provided to all fluorescent and discharge type lighting fixtures. Mechanical equipment is served with 460V three phase power through control panels and power distribution panels connected to a mechanical equipment riser.

The Bloomberg Tower is also provided with a life safety riser and elevator power risers. A 1750kW diesel powered emergency generator is used to supply the life safety emergency loads and specified tenant loads. The emergency power distribution system includes automatic transfer switches and control devices for automatic start-up in case of normal power loss. A 10,000 gallon steel fuel oil storage tank provides fuel for the emergency generator.


All public areas of 731 Lexington are provided with lighting. Control of the public area lighting and exterior lighting is maintained by the building management system. Typically, the office spaces consist of recessed lighting fixtures. More specific information on the lighting design will be available upon receipt of the electrical drawings.


Primary cooling is provided to the Bloomberg Tower by a chiller plant located on the 8th floor east mechanical equipment room. The room includes 6- 1165 ton chillers, 4- 1000 ton plate and frame heat exchangers (for retail condenser water and chilled water free cooling), seven primary condenser water pumps (including one standby), three secondary condenser water pumps serving the retail spaces, seven primary chilled water pumps, and four secondary chilled water pumps distributing chilled water to the office floors and plate and frame heat exchangers for the residential floors. An 8,000-ton cooling tower is located on the east core roof. Capped chilled water outlets (6”) are provided on the east and west cores of each floor for up to 775 tons of supplemental cooling.

High pressure steam, purchased from the Consolidated Edison HPS utility grid, is the primary heating source. This steam is reduced to low pressure steam through a pressure reducing station. This low pressure steam is then distributed to hot water heat exchangers serving the office space. Hot water pumps are used to distribute hot water to perimeter radiation and unit heaters. Low pressure steam is provided to shell and tube heat exchangers for heating the residential floors.

The office space is air conditioned using a VAV system. Low temperature, conditioned air (48F DB) is distributed through medium pressure risers with automatic isolation dampers. Air is returned through hung ceiling plenums with dampered return air outlets that connect to return air riser shafts.


Two- 6” domestic water services are brought into the building via 58th and 59th streets. The domestic service provides water for a 40,000 and 10,000 gallon suction tank. The 40,000 gallon tank serves the Bloomberg office space using a VFD pumping system. Plumbing fixtures in the office core are provided with hot water from local electric hot water heaters. Triplex house pumps supply the main house tank, which is located on roof- 3. The base building suction tank utilizes a dedicated triplex constant pressure booster pump system, which supplies the retail and base building areas. Plumbing fixtures located in lower levels will flow by gravity. Combined city sewers will serve the entire building. A complete storm drainage system is provided from all roofs, set backs, plaza and area drains.



The entire Bloomberg Tower is protected with an automatic wet sprinkler and fire standpipe system except electrical closets, telephone closets, and telecommunication rooms, which are provided with smoke detectors. Lower level 3 through floor 12 are served by a 750 GPM, automatic fire pump, while a 750 GPM manual fire pump serves all floors in the building. All fire pumps have controllers with automatic transfer switches that are connected to the emergency generator.

A class ‘E’ fire alarm system is provided to the base building, which excludes the residential floors. This fire alarm system includes manual pull stations, smoke detectors, visual strobe indicators, and water flow and tampering switches. The residential portion
of the building will be protected with a class ‘J’ system. The fire alarm systems are connected to a monitoring system that transmits the alarm to the fire department.

In addition to the fire alarm systems, the building houses a Fire Command Station (FCS) that provides centralized control of the alarm zones. A Voice Communication System (VCS) provides evacuation signaling through ceiling mounted speakers located
throughout the building. In addition to the FCS and VCS, the Bloomberg Tower is provided with a Firefighter Telephone System (FTS) allowing two-way communication between the Fire Control Center and dedicated phones in elevators and elevator lobbies.


Twenty-nine elevators serve the Bloomberg Tower. These include a low, mid, and high-rise bank for the office areas, a bank of three elevators serving the residential floors, and three freight elevators that also serve the office levels. The retail areas are provided with five freight elevators and a truck lift from 59th street.


A Service Entry Room (SER) located on the south side of Lower Level Two, along with several telecommunications closets, house the telecommunications services. The SER contains multi-pair, copper cable termination equipment, fuse protection, and single/multimode optical fiber cable termination equipment. Two duct banks enter the SER from opposite sides of the building and an intra-building pathway system is used to route the telecommunications cabling throughout the building. Cable TV service to the building is located in the telecommunications closet.


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