Live from a double-rainbow kissed Morrisette Campus, It’s the Thermal Mass and Buoyancy Ventilation Research Project team! Recently, as the chill rolls into Newbern, the students and faculty witnessed this heart-warming phenomenon. And if you came for the rainbows, you should stay for the structure. Hang tight to learn how the TMBVRP team is supporting the Test Buildings eight feet off the ground.
One more thing before we get on to the structure, a quick look at the Horseshoe Courtyard. During this semester the TMBV Research Project team has enjoyed working on the Horseshoe Courtyard site. Every Tuesday, project teammates Caleb and Claudia are wonderful and patient teachers to the TMBV team. The team certainly appreciates the construction experience and the time away from their computers. Go check out all of the beautiful work the Horseshoe Courtyard project team has done on their blog!
Model on Mock-up montage Cooling Porch seating arrangement mock-up
First, a quick reminder of how and why the Test Buildings are up on stilts. Because the Optimal Tuning System uses thermal mass to create airflow, the Test Buildings will expel cooled air. In the Summertime, that cooled air could be a benefit to more than just the Test Building dwellers. Therefore the Test Buildings design was lifted in order to create a Cooling Porch underneath. Here, anyone can enjoy an outpouring of chilled air. The team chose steel columns to do the heavy lifting to keep the focus of the space on the solid Downdraft Chimneys. As seen in previous blog posts, the column’s placement is dictated by the relationship to the Downdraft Chimney’s and the seating arrangement. However, the column arrangement can not just look good on paper and feel right in the mock-up, it’s got to actually, safely stand up.
Thankfully, structural engineer Joe Farruggia approved the column placement—now it was time to size the columns. Through a series of hand calculations, the team tested the stiffness of 3.5″ – 6.0″ diameter steel columns to see which ones could handle the weight of the pods. Then, Rowe took this work into Intercalc, an engineering software. Intercalce allowed him to test structural loads such as gravity loads, wind loads, live loads, and overturning forces. It turns out a 5″ O.D. steel column will be more than safe. Now, onto bracing!
Plan showing braced columns within the berm wall
Three of the four columns, per test building, are braced to eliminate excessive drift caused by wind loads on the tall faces of the buildings. Similarly, bracing the columns reduces possible deflection and improves stiffness. The column bracings, hidden in the berm walls surrounding the Cooling Porch, are 4″ x 4″ x 3/8″ steel angles. The six braced columns appear 5′ tall as they disappear into the berms while the other two are the full height of the occupiable space at 8′ tall. These taller, unbraced columns act as entrance markers.
Originally, the team believed a concrete ring beam foundation would be sufficient for fixing the steel columns, and thus the buildings, solidly to the ground. As seen in the drawing above, the ring beams would extend to catch bracing. However, the team needed to consider overturning moments, or overturning forces, due to the height and the aforementioned wind loads of the Test Buildings. Overturning moments are those applied moments, shears, and uplift forces that seek to cause the footing to become unstable and turn over. This means they needed to make sure the foundations were strong enough to keep the columns and bracing in the ground during bad storms.
Before these moments could be properly designed for, the team needed to do some soil testing. The quality, based on its compaction, of the soil is another factor in determining the necessary size, and strength, of the foundation. Jeff and Cory dug some holes and then used a penetrometer to test the soil. And who would have thought—the site has some pretty decent soil! Unfortunately, Jeff has been stuck in that hole for weeks… We miss you Jeff!
To counteract the overturning forces, the foundation changed from a ring beam to a buried slab foundation which increases its weight. Each Test Building will have its own foundation. The slab foundations secure all columns and bracing to each other as well as the ground. Below are currents drawings of the foundation, column location, and bracing connections.
Foundation Plan showing concrete curb seating Foundation Plan highlighting relation to columns and gravity loads A section of the whole shebang
The Thermal Mass and Buoyancy Ventilation team will be jumping into drainage and ground material master planning next. Translating research into design into construction has been an arduous journey. However, the pay off will be worth it when designers anywhere can use the Optimal Tuning Strategy to make building materials work as air conditioners. Thanks for reading and stay tuned!