Structures
Adventures in Renovation: The Historic Courthouse and the Stair and Elevator Tower Conundrum By: Andrea Righi
The Theodore Levin US Courthouse in Detroit, built in 1934, is a beautiful example of Federal Post Office and Courthouse architecture of the early 20th century. After 80 years of continuous operation the building required significant upgrades to provide tenants with code compliant, state-of-the-art facilities and Class A office space. In 2014, Page began work on a phased modernization project for the 770,000 SF occupied historic courthouse. A building-wide life safety analysis determined that the two existing egress stairs were insufficient to meet the population based on current building codes. To remedy this, the design team was tasked with adding a new egress stair that discharges to the exterior of the building. This element, along with new service and passenger elevators, form a new vertical transportation tower for the building. This article will specifically discuss the tower design process and complexities encountered during construction. What happens when you need to add a new stair and elevator tower to a landlocked historic building? Additions are commonly made to the side of a building, which simplifies the structure and creates one plane where the new interfaces with the existing. In the case of the Theodore Levin US Courthouse, however, the existing building occupies an entire city block and the upper floors are arranged in a “donut” shape with offices and courtrooms surrounding an interior light court. The only option was to figure out a way to route a new stair through the existing building. The solution needed to solve the code compliance issues in a manner
that limited the impact of the stair on the existing building, preserved historic materials, minimized impact on existing circulation, and allowed continuous building operation. Ultimately, a location in the center of the building was selected that allowed a narrow connection to the historic interior courtyard face but otherwise allowed the tower to be an object within the light court. What worked well for the upper floors to minimize disruption became challenging on the interior of the building. A significant number of MEP systems, some active and some abandoned, needed to be demolished and moved out of the footprint of the tower just under the second floor roof. On the first floor, the location meant that the tower would go through the middle of the existing arraignment courtroom. Since the other benefits to this location were so compelling, the US Courts and the General Services Administration determined it was worth moving the courtroom to a new location and relocating the MEP infrastructure to make way for the new structure. The design and construction team worked through the phasing challenges to sequence the work in a manner that coordinated with the project schedule. While the tower program was relatively simple, the structure itself is complex. Early on, it was determined that the new structure could not be connected to the loads of the historic building. The structural engineer of record, Ruby + Associates, designed a completely freestanding 200-ft tall tower with slip connections to the existing structure. New micropiles were drilled to support the tower foundations and massive structural steel columns were set in place to support the tall tower.
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csengineermag.com
NOVEMBER 2023
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