In this episode, we talk to René Vignos, SE, a structural engineer and Principal with Forell/Elsesser Engineers in San Francisco, about retrofitting historic buildings and how engineers can help preserve and protect historic landmark structures. Engineering Quotes: Here Are Some of the Questions We Ask René: What interests you about working on projects that preserve historic structures? What are the first steps you take when you start one of these projects? What are some of the challenges with retrofitting historic buildings in seismic zones? Why and how have you used base isolation technology to retrofit historic buildings? What have been some of the challenges in using this technology in a historic building? What challenges did you face in retrofitting Memorial Stadium at UC Berkeley and how did you overcome those challenges? What are some of the things engineers can do to help preserve and protect historical sites? Do you have any advice for young engineers starting in their careers? Here Are Some of the Key Points Discussed About How Engineers Can Help Preserve and Protect Historic Landmark Structures: To enjoy working on projects that preserve historic structures, you must enjoy the history behind the structure. Seeing the old drawings that were done more than 100 years ago is quite an experience. Looking at how much time the workers put into making all the details in the building is very enjoyable. Many things must be done when starting projects that preserve historic structures. All the drawings that you can find of the building must be gathered. There could also be photos of the early construction of some of the historic landmark structures that can also be a great help in understanding their cladding systems. Tour the structures thoroughly and take as many photos of them as possible. The materials used must be taken into consideration. Pull testing rebar, brick tests, and laser scanning are some of the tests that must be done. Most historic landmark structures are built using unreinforced brick, nonductile concrete, and an array of heavy brittle materials. The heavy building materials make the structure heavy, and the seismic force is related to how heavy the structure is. Having highly brittle materials and high seismic forces can make it difficult to find a way to get structure in the building to make it work. Very robust systems like concrete can be used, but preserving the historic element that everyone wants to see must always be of utmost importance. Base isolation is separating the building from the ground laterally. When the ground shakes violently, the isolators filter the vibrations out and the building gets a small fraction of the seismic energy. It reduces the movement and the force that the building experiences. Base isolation can be a technical task because the historic landmark structures are heavy and brittle. An active jacking method is used by inserting needle beams through a wall that can be individually jacked up to lift the wall and replace the foundation with the isolators under it. The Memorial Stadium at UC Berkeley was primarily constructed with non-ductile concrete, which made it very brittle. This big, brittle structure is sitting on an active earthquake fault. The exterior wall is the main part of the structure that everyone wanted to preserve, so a new structure was built behind the exterior wall to save and preserve it. Bunker-type structures were built under the parts of the stadium that were on the earthquake fault. It allowed those parts of the building to move in response to what the ground is doing. Engineers can help preserve and protect historical sites by checking things in the code for historic buildings. Have a mindset of thinking outside the box and doing thi...