- The State of Utah hired Forell/Elsesser Engineers to assist with a complete historic preservation and base isolation retrofit of the historic Utah State Capitol building. Completed in 1916, the capitol building is a monumental four story, reinforced concrete, 320,000 s.f. building with granite cladding and a large copper-clad concrete dome. The structure’s majestic dome stretches 165 feet above the rotunda floor and the outer dome rises 235 feet above the ground. To protect this massive, yet ornate building, Forell/Elsesser Engineers and Reaveley Engineers have strengthened the building using 256 state-of-the-art seismic isolators under the Capitol Building. During an earthquake, the ground and Capitol will move independently while the isolators deform, stretching sideways up to 24 inches in any direction, thus protecting the building, its people, its contents, and its history.
- One of the main challenges to retrofitting any historic building with base isolation is the temporary support of the existing structure while inserting isolators and creating an integrated final support system. In the case of the Utah State Capitol, this challenge was intensified by the weight carried by each of four large piers/footings that support the rotunda dome and surrounding floor area. For reasons of safety and economy of construction, Forell/Elsesser Engineers developed a method of permanently re-supporting the rotunda of the Capitol with a unique circumferential post-tensioned concrete load transfer scheme that obviated the need for temporary support of the existing footings, eliminated the risk of differential settlement, and minimized the need for excavation and demolition. The resulting transfer system also eliminated the need to excavate beneath the existing foundations. The system consists of large concrete beams that wrap the existing pier footing. These beams form a single composite section with the existing footing and span 51 feet between girders. The supporting girders each rest on four isolation bearings. Not only does this solution provide superior performance in consideration of the lives of building occupants, it protects the building itself, the single most valuable, prized and historically significant structure owned by the State of Utah.
This landmark building in the State of Utah was seismically protected by inserting a base isolation system below the existing historic structure. Under the main historic dome, Forell/Elsesser Engineers developed an innovative temporary and permanent support solution that separates the rotunda from the ground and the violent shaking of an earthquake. Customized Solution
- Architect: VCBO Architects, Engineer of Record-Reaveley Engineers & Associates
- Owner: State of Utah
- Base Isolation of an historic concrete structure
- The final system supporting the entire dome of the Capitol transfers 28,000,000 pounds of load from the original 30’x40’ footings to 32 new isolators.