Building Statistics - Part 1
General Building Data:
This high-rise is the first multi-tenant new office construction that Pittsburgh has had in decades. The project is aiming to achieve LEED Silver, and will be a mixed space with retail, 20,000 square feet of office space, a garage with 330 parking spaces, and nearly 200 hotel rooms. This high-rise will be close to Pittsburgh’s Cultural District, North Shore connectors, over 100 restaurants, and many forms of entertainment.
The façade of the structure is mainly composed of large curtain wall systems and metal panels, with concrete-masonry block used on facades that abut adjacent buildings. The structure has also been designed to have an alternate green roof garden feature to allow for more green space in the urban setting.
The façade of this building is fairly consistent and limited with the materials. Nearly every exposed face of the building is composed of vision glass, spandrel glass, metal panels, and metal louvers. The metal panels and louvers are metallic painted steel that will have both interior and exterior primer finishes. The lower retail spaces and the unexposed facades (facing other buildings) are an 8” concrete masonry unit wall due to the close proximity to adjacent spaces preventing further exterior finishes. The roofing is 3” corrugated metal deck that has an overlaying system composed of TPO (Thermoplastic Polyolefin) Roofing and Fluid-Applied Protected Membrane Roofing. The TPO will withstand uplift pressures, reduce thermal movement, and shall remain watertight throughout exposure to weather. The Fluid-Applied Protected Membrane Roofing will improve the lifecycle of the roof, while also reflecting solar radiation in order to reduce energy costs.
This project is aiming to earn a LEED Silver certification based upon the 2007 LEED Reference Guide for Green Building, Design & Construction Version 2.2. Some of the means by which this rating will be achieved include the coordination of the curtain wall R-values and the loads of the rooftop air handling units, a bike rack, local resources and materials, and separate sanitary and storm lines. In addition to aiming for LEED Silver, alternative designs for a Green Roof Garden have been designed, but they will only be implemented if time and resources are available further along in the project.
Building Statistics - Part 2
Excavation & Earth Retention:
At the start of the project, the site required a fair amount of excavation to prepare for foundations. Prior to this project there were 7 businesses spanning the north side of the site, so earth, old utility lines, and former foundation systems were removed from the site’s footprint. Due to the site being surrounded along the East and West sides by existing buildings, there is no need for retention walls; however, it is crucial to monitor the condition of the basement walls as they are exposed during the excavation to ensure that excavation could be completely successfully and safely. The proposed and approved backfill for the excavation and foundation work is a crushed and screened concrete/masonry material that is to be compacted to a minimum of 100% of its maximum dry density.
The contract for this structure is a GMP with the Construction Manager at Risk. Turner Construction was awarded the project as the Construction Manager promising a guaranteed maximum price of $67,000,000. In addition to Turner Construction being a Prime Contractor, Scalise Industries has been awarded the MEP Prime Contractor title. Being that The Gardens is located in the heart of a large city, site congestion and access requires careful and intricate consideration. The prime contractors, as well as several subcontractors, were able to rent out space in one of the buildings adjacent to this site. This ultimately saved space on the already congested site, while also providing ideal access to the construction at hand.
Aside from maintaining a schedule and a budget, the pedestrian traffic in the area took a high priority when it came to restricting access to the site and preserving the safety of those who regularly came near the site in the city. After establishing a means of access to the site and finalizing contract details and finances, construction began on January 13, 2014 with a 23 month duration that is currently aiming for an expedited 21 month schedule in hopes of a substantial completion date in early December of 2015.
There are three different structural systems that are used throughout this building to serve three very different spaces. The entire building’s structural system will be supported by a system of mat foundations, grade beams, auger cast piles, and footings accompanied by a backfill of crushed/screened concrete. The structure above grade will consist of wide flanged W14 columns that will span several stories and will range in size from a W 14x43 to a W 14x426. Between these columns span various series of wide flanged beams and girders to support each floor and slab. These beams and girders can be found in a range of depths from W8-W44 that vary in weight. The structure is also comprised of composite metal deck, concrete, and hollow tube steel components; however, these are separated into the aforementioned “three” separate spaces.
The first of these regions is what is called the podium. The podium is comprised of the first three levels of the structure which will house the garage ramp, retail space, a portion of the garage, and the restaurant space for the hotel. The first floor will span a height of 17.5 feet, while the next two floors will be 12 feet in height. The retail space floors are not to be finished within the contract, so they will have 4” of crushed aggregate on grade, while the other spaces on the first floor will be 4” of slab on grade concrete over 4” of the crushed aggregate. The remainder of the parking garage (in the podium and beyond) will be a 5” post-tensioned, normal weight slab, except over the retail space there will be a 4” wearing slab. The hotel slab within the podium region will be a 3 ¼” lightweight slab over a 2” 18 GA composite metal deck. The remaining hotel space above the podium will be 3 ¼” lightweight slab over a 3” 18 GA composite metal deck, while the office space will be a 3 ¼” lightweight slab over a 2” 18 GA composite metal deck. In addition to the columns and beams throughout the hotel region, there is a hollow structural steel system that spans from levels 4-1. These members are 4”x4” and have a thickness range of ¼” to ½”.
The mechanical systems and the electrical systems are much more straightforward and simple in retrospect. The mechanical system will be comprised of six rooftop air handling units. Two of the units will be 50,000 CFM for the office tower and will contain enthalpy wheels to supply the region with air. The other four will be for the hotel corridor (12,000 CFM), office lobby (1,600 CFM), kitchen (4,000 CFM), and the laundry room (3,600 CFM). These air handling units will feed the entire structure through ducts and exhaust fans with the exceptions of the garage (it is open to outside airflow), the hotel rooms, and the retail spaces. The hotel rooms will each have their own self-contained packaged terminal air conditioning units (PTACs) that are thru-wall units and will have an outside air CFM of 70. The retail packages are to remain core and shell and will be designed and outfitted by the respective tenants.
The buildings electrical service is owned by Duquesne Light and is fed by 6, 3-½” conduit containing 4-#600MCM and 1#400EGC and 7, 4” conduits containing 4-#750MCM and 1#600EGC . The 3-½” feeders are providing power to a 277/480V main switchboard sized at 2000A and the 4” feeders are providing power to a 277/480V main switchboard sized at 2500A. From these main switchboards there are 65 panels throughout the structure.
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