Topped out! Another Seismic Retrofit in Washington County Takes Shape
Last week we celebrated the topping out of the Charles D. Cameron Public Services Building (PSB) in Washington County, marking the completion of exterior shear walls on the building’s north wing.
It has almost been a year since construction started on the PSB, and two years since design wrapped up – a truly celebratory occasion for the team. As the project designer Gauri Rajbaidya and I stood there and looked at the new corners, we reminisced about the how we got there.
With every seismic upgrade there is a design approach that jumps out as the ‘right one’ for that building. For the PSB, we explored only exterior solutions since the basement walls needed waterproofing to mitigate an existing infiltration issue. It made financial sense to excavate around the building once, and piggyback on that activity for the new structural footings.
We explored various exterior frames, but they looked odd on this 1980s, formal institutional building; and alien on Main Street in downtown Hillsboro. Additionally, the collector steel needed to tie the frames into the existing structure would run deep into the floor plate and disrupt more of the interiors. But concrete shear walls integrated with the existing precast and the collector steel could run parallel to floor slab and keep the disruption to the exterior wall.
Bassam Khalifeh, the County’s Senior Capital Improvements Project Manager, said the solution “looks like it was original to the building.” We agree!
The site-cast architectural concrete complements the language of the existing materials and shows how the building was seismically retrofit. So often in seismic upgrades, the structural work is hidden behind walls, which makes it hard to explain where the money went. For many months now, constituents of the county have seen the earth be pulled back, complicated rebar cages be built around the corners, and formwork be lifted into place.
This design was a win-win solution: It offered new site design, windows to the basement, structural and non-structural seismic strengthening, and water mitigation for the basement. A shoutout to the construction team at JE Dunn, who have safely completed some very difficult work, as well as to staff at the County who have been patient partners during construction!