As part of my involvement with a mixed-use development project I was asked to help advance a number of design elements that were left largely unresolved in the conceptual design phase. Now that we had buy-in from the client, it was time to study how our project was actually going to be built. I was left in charge of one particular feature, a large square planter and seating element in the building's entry courtyard.
Wilson Meany / Perkins + Will
Lead Designer for this Object
Skills / Tools
Sketchup, Lumion, Illustrator
In the previous design phase this seating element was just shown as a continuous concrete square measuring 30' x 30'. Although it could be built in one piece using a cast-in-place method, our team preferred to use a pre-cast method which would result in a more refined and cost-effective final product. The design challenge was to break down the shape we had into modules that could be easily cast and transported. Since creating custom molds would be the greatest factor influencing cost, a key objective was to create as few unique modules as possible.
Before breaking up the bench into modules, I had to first refine the bench in section, making sure I had an appropriate shape to iterate on. For this effort I took the rectangular shape that was drawn as a placeholder in previous design phases and modified it to work at a human scale. I looked to architectural ergonomic standards to create a comfortable seat, lowering the seating surface to 18"x18", providing a 22" back height, and angling the seat back to 80°.
Now that I had a properly dimensioned form to start with, I began to brainstorm ways to break it up into modules. Since the design concept for this bench was to serve as a frame for the plants inside, I took inspiration from techniques used for years by frame-makers. After sorting through a number of examples I decided to further explore two options which I found to be the most promising; half-lap jointing and mitered jointing.
Although I had an idea of how the modules would fit together, it was imperative to understand how they would work in 3D. I began by making a properly dimensioned model in SketchUp of each module, and then arranged the modules to form the full shape. In these schemes, the bench consisted of four modules, each 30' long in diameter. Both of these designs seemed to work at first glance, and I brought them to share at our design team meeting later that week.
Later that week at our design meeting, my team members appreciated that I solved the challenge of designing the bench using just one unique module. Our team was really excited about the solution, and took it to one of our construction advisors for review. Although the design worked on paper, our advisor warned us that creating a 30' long mold for a module would be out of our budget. In order to keep the cost to a minimum, it would be ideal to have 10' long modules at maximum.
I went back to the drawing board and tried to break down my initial design into thirds, keeping each module 10' long. I went through a number of iterations, but kept running into the same problem each time. It turns out that due to the offset of the bench seat and the bench back, the corner condition will always be unique from the condition at the straight segments. I came to the conclusion that due to this recurring issue, the only way to solve our problem would be by having two unique modules.
With this new constraint in mind, I began breaking down the 10' modules into even smaller pieces. For the half-lap option, I came up with a solution that would allow the modules to overlap in both straight sections and at corners, with an intermediate piece to fill the gaps that were created by dimensional constraints.
For the mitered option, I had to abandon the original concept and simplify the design even further. Instead of being mitered at the corners, the corners were now their own unique modules acting as cornerstones. The rest of the modules were now simple 10' long pieces with regular edges. After another round of review, the design team unanimously agreed that this option was preferred due to its simplicity and elegance.
Now that I had a modular system in place for the bench, it was time for a final round of iteration to refine my design. Our team decided that using wood in the design would add material diversity and create a more welcoming seating surface. In order to accommodate this design change, the concrete form had to be modified, dropping what was previously the concrete seating surface to fit the dimensional wood pieces. As a minor aesthetic change I angled the outside edge inward to create a slight reveal on the underside of the bench. Both of these changes were reflected in the final form of the concrete modules.
At the end of this design process I left our team with an elegant, simple, and cost-effective solution that was still aligned with the original concept from earlier design phases. My efforts on this project left a valuable precedent for the office, as I overcame technical constraints to create a modular precast concrete system. When built, this bench will be the centerpiece of the building's entry courtyard, providing both aesthetic and functional value to the overall development.