Tomochichi Federal Building – Savannah, GA

By Mark Palmatier | April 4, 2024

Scaffold Design

With a lineage that forges a path from the creation of our Union through some of the most significant events in our county’s heritage, Savannah, GA, has no shortage of historic and awe-inspiring buildings. This is why D.H. Charles Engineering was honored to work on the restoration of one of the city’s architectural stalwarts, the Tomochichi Federal Building and U.S. Courthouse. Originally designed and constructed in the late 1890’s, the courthouse has been a cultural icon for over a century in what is now the heart of Savannah’s historic district and is listed in the National Register of Historic Places.

 

Slated for significant interior remodel and exterior repair, DHC was tasked with providing a worker access solution to allow for the restoration of the historic 130-year-old stone façade of the courthouse’s iconic tower. Due to the extremely tight constraints of the job site, a work deck design was also requested. Ultimately, a solution took shape: a 43’-wide x 68’-long steel platform frame would form the backbone of the work platform, supported over the courthouse roof and 75’ above the city streets. Upon that framework, a 34’-wide x 43’-long work deck and laydown yard would be built to facilitate construction activities on the tower without impacting the flow of everyday traffic below. In addition to the work platform, the steel framing would support the 72’-tall access scaffold system that would allow for the restoration of the courthouse tower. To allow for access around the entire tower, the steel framing cantilevered 7’ beyond the roof of the structure, hanging over the interior courtyard.

 

 

The main portion of the platform spanning over the roof was supported by steel columns that tied into the existing masonry wall which made up the central hallway of the courthouse. To ensure a solid footing for the platform, the columns bypassed the roof entirely and were bolted directly to the wall structure. While unavoidable, we did not take tying into and setting on 130-year-old brick walls lightly! During pre-construction planning, two DHC engineers visited the job site and surveyed the condition of masonry walls where the columns would land to ensure they were in good enough condition. Then, during the design phase of the platform, the structural adequacy of the masonry walls was calculated to verify they would provide the necessary support.

 

 

At the street side, the platform was supported by 75’-tall heavy duty shoring towers that set on the sidewalk below. This would allow trucks to pull right next to the platform and unload directly to the work deck via a material hoist lifting material straight up from the street. From the outset of the design, ensuring the overall lateral stability of the platform was a key design question, with the street side section as a specific focus. When work is being performed that high in the air over an active city, an unstable work surface is the last thing anyone wants. The project duration was relatively short in comparison to a permanent structure, so wind was the governing lateral force to resist. The full temporary structure, including the scaffold, platform deck, and shoring towers, were modeled to determine the worst-case tie loads at each restraint point to ensure no single location was a focal point for loading. Anywhere the platform interacted with the courthouse structure was secured with epoxy anchors into the masonry walls. However, at the shoring towers where there was no courthouse structure, cables were alternatively secured to concrete deadmen. To limit sway in the platform, a pre-tension was calculated and implemented to reduce sag.

 

The lateral stability of the platform got an unexpected test when it had to ride out the Category 4 Hurricane Idalia while still being installed. With sustained wind speeds of 115 mph and peaks of 130 mph, the wind forces were significant. But when the storm cleared, the platform had made it through with no damage! DHC always brings valuable engineering experience to both the smallest & most high- profile jobs. Contact us for your next construction project!

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