Serving as a sub consultant to the Architect, PDC provided Structural, Civil, Mechanical and Geotechnical engineering services for this new residence hall that houses up to 60 beds (with future growth planned to a minimum of 120 beds).
The new residence presented the structural design team with many challenges and opportunities for innovative design. Major challenges included designing for construction in an extremely rainy climate, ensuring proper foundation support despite sloping terrain and varying soil conditions across the site, supporting complex rooflines, and incorporating changes to construction scope late in the design process. PDC engineers worked diligently with all members of the design and construction team to complete this unique facility on schedule and exceed the client’s expectations.
With three different structural systems utilized in the building, and four seismically separated portions of the facility, creativity and attention to detail were needed. PDC’s approach was to design load-bearing cold-formed steel (CFS) structures that sandwiched the central structural steel gathering structure and provided seismic joints between the independent structures. The front entrance canopy, framed in glulam wood, was seismically separated from the warm building structures. The three different structural systems were selected to provide the best fit for the architectural layouts, efficiency of materials, and sustainability considerations.
Site geology contained both bedrock surfaces and deep lenses of organic material requiring diligent subsurface investigation to identify these two different site conditions. Site investigation methods for the four-story residence hall included machine dug test pits and hand exploration methods to map the bedrock surface and model it in Civil 3D site design software. Of particular concern was the fact that half of the building would be bearing on bedrock surface, and half the building on an engineered embankment surface. Siting of the building with these varying site conditions included very close coordination with the structural engineer, architect and the Owner.
The civil engineering design for this one-acre, undeveloped, sloping, forested site included clearing and grubbing, and site preparation for the building foundation. An extension of the domestic/fire water supply was provided. Design components also included a new sanitary sewer system connecting to Glacier Highway; new underground storm drain system; erosion and sediment control plans; and traffic control plans for the Glacier Highway sewer connection. Challenges of the varying site soil conditions required the bedrock surfaces to be modeled to determine the limits of rock excavation required to safely support the building foundation. Site work was designed and permitted to be constructed in two phases. Close coordination was maintained throughout the project design phase with the entire design team to ensure that the building footprint and building foundation system aligned with the bedrock excavation.
IBC special inspections were performed on the construction of the new facility. Special inspection services included earthwork, reinforced concrete, epoxy grouted anchors, structural steel bolts, structural steel welding, and cold-formed steel. In addition, engineers &M performed water sample testing per City and Borough of Juneau requirements, compaction testing within the State of Alaska Department of Transportation right-of-way for the sewer manhole installation, and observation of water and sewer pressure testing procedures in accordance with the project specifications.
The mechanical systems design included air source heat pumps with an electric boiler backup heating plant, radiant floor heating, heat recovery ventilation, low-flow plumbing fixtures, wet sprinkler and standpipe systems, propane emergency generator, and direct digital controls.