Ohio State University’s Knowlton Hall is much more than a new home for the Austin E. Knowlton School of Architecture. A showcase for architectural possibilities, Knowlton Hall serves as a stimulating learning environment for its students. The new facility brings together the schools of architecture, landscape architecture, and city and regional planning, which had previously been housed among several scattered, outdated buildings across the OSU campus. Today, the four-story, $32 million Knowlton Hall provides a modern, 168,000-square-foot facility containing classrooms, auditorium, 30,000 volume library, assembly spaces, faculty offices, and studio spaces for more than 600 students and faculty who use the building on a daily basis.
The architect’s vision for dramatic structure, unique forms and interaction between spaces to create a feeling of connection for the occupants could not have been achieved without the use of concrete. The project includes nearly 7,000 cubic yards of mild steel-reinforced concrete walls, columns, caissons, grade beams and slabs-on-ground, and 8,000 cubic yards of post-tensioned elevated concrete slabs.
Many of the 12-inch thick floor slabs are cantilever and are left exposed, creating an impression of slabs floating in space. The floating effect is most prominent at the interior edges of the vertically offset third-floor quadrants, where flights of stairs appear to defy gravity as they span between the levels. An overhanging cantilevered slab, that supports a walled roof garden above, shelters the main entrance of the building. This 32-inch thick post-tensioned slab cantilevers 26 feet from a cluster of three columns and spans 50 feet across the entrance. The total prestress force in the cantilever section is five million pounds.
On the third level, studios feature ceilings up to 30-feet high, with columns spaced as far apart as 40 feet, creating an expansive space. A majority of the façade juts out prominently at the third level, requiring the 12-inch thick slabs to cantilever as far as 10 feet at the third level and 13 feet at the roof. The designers took into account the difference in deflections between the studio roof and floor slabs, which differ greatly in their loadings, cantilever lengths and support conditions.
The spine of the building is a 16-foot wide, full-height circulation space that contains more than 1,300 lineal feet of gently sloping ramps. The ramps seem to float in space as they cantilever seven feet on either side from 16-inch-thick concrete walls. The ramp walls are spaced up to 32 feet apart, requiring extensive post-tensioning and steel reinforcement in the slabs. Placement sequencing and construction joint location was critical to the performance of the post-tensioned ramp slabs.
Post-tensioned concrete was selected as the best solution for the architectural vision of this building. The selected system allowed for the thin structure, large column spacing, dramatic cantilevers, and high live-load requirements. The post-tensioned concrete system drastically reduced the quantities and the congestion of steel reinforcing bars that are prevalent in conventional concrete slabs. Cracking in the exposed post-tensioned floor slabs has been virtually eliminated, creating a much more pleasing appearance. The use of exposed concrete as the finished product helped save hundreds of thousands of dollars in floor and ceiling finishes throughout the entire project.
Ohio State University, Columbus, Ohio
Mack Scogin Merrill Elam Architects, Inc., Atlanta, Georgia
WSA Studio, Columbus, Ohio
Shelley Metz Baumann Hawk, Inc., Columbus, Ohio
P.J. Dick, Inc.; West Mifflin, Pennsylvania