“Eliminating our reliance on heavy structural members by making the glass do double duty is a great strategy on several levels: It reduces unnecessary weight and mass while reducing obstructions to view or natural light. By multiplying the performance value of the glass in consolidated ways, they have made the R+D process more meaningful.”—Juror Doris Sung
Glass is the ubiquitous modern material, but its structural qualities remain relatively unexplored.
Enter a collaborative research team initiated and led by Masoud Akbarzadeh, the director of the Polyhedral Structures Laboratory and assistant professor of architecture at the University of Pennsylvania's Weitzman School of Design. The team also included designers, researchers, and practitioners from Villanova University, The City College of New York, the Technical University of Darmstadt, and Eventscape. They developed Tortuca, an ultra-thin hollow glass structure, which spans 10.5 feet with an assembly of 13 hollow glass units. Using polyhedral graphic statics to optimize the structural form, each five- or six-sided piece is composed of a sandwich of two float-glass deck plates held together by either glass or acrylic side plates that vary based on their location within the composition.
While the fabrication requires some high-tech machinery, there’s a limited need for labor during assembly. Five-axis abrasive waterjet cutting creates the precisely dimensioned glass panels. Acrylic side plates are created through five-axis CNC milling. Each hollow glass unit can be assembled within an hour by just one person. The pieces are bonded together using 3M VHB double-sided transparent structural tape. The complete structure weighs just 550 pounds and can be assembled and disassembled by a single individual without heavy machinery. The 13 pieces are held together through acrylic locking bars. To date, the glass bridge is limited to supporting its own weight. The team plans to test it under other loading scenarios in the future.
“Our design decisions emphasize the primary role of glass and the purity of the structure,” says Yao Lu, the project architect. “Tortuca is educational, illuminating, and full of possibilities; it’s still in the early stage.”
The immediate next step will be a physical load test for Tortuca. “With the data obtained from the physical test, we will move to the optimization, fabrication, and construction of a 10-meter experimental glass pedestrian bridge designed using the same modular construction system,” Lu says. The team posits that minimizing construction material and using the purest form of each material—glass and acrylic—may potentially preserve natural resources and curb energy demands in building and infrastructure projects.
While the ultimate outcome of these hopes seems less than certain, glass may prove to be a more versatile ingredient in new structural systems.
Principal Investigators: Masoud Akbarzadeh (Polyhedral Structures Laboratory, University of Pennsylvania), Joseph Robert Yost (Department of Civil and Environmental Engineering, Villanova University), Mohammad Bolhassani (The City College of New York), Jens Schneider (Technische Universität Darmstadt)
Project Architect: Yao Lu (Polyhedral Structures Laboratory, University of Pennsylvania)
Project Team: Yao Lu, Ali Seyedahmadian, Philipp Amir Chhadeh, Matthew Cregan, Mohammad Bolhassani, Thomas Lee, Matthew DeLissio, Vincent Micozzi, Tristan Fischer-Smith, Joseph Robert Yost, Jens Schneider, Gareth Brennan, Masoud Akbarzadeh
Structural and Computational detailing: Yao Lu, Masoud Akbarzadeh
Structural Analysis: Philipp Amir Chhadeh and Mohammad Bolhassani
Structural Load Testing: Joseph Robert Yost and Mathew Cregan
Fabrication and Assembly: Yao Lu, Ali Seyedahmadian, Thomas Lee, Vincent Micozzi, Tristan Fischer-Smith, Gareth Brennan
Five-Axis Milling Services: Eventscape NY
Plywood Formwork: Eventscape NY
Metalworks: Eventscape NY
Five-Axis Waterjet Services: AquaJet Services LLC
Funding: This project was supported by University of Pennsylvania Research Foundation Grant (URF), National Science Foundation CAREER AWARD (NSF CAREER-1944691-CMMI) and the National Science Foundation Future Eco Manufacturing Research Grant (NSF, FMRG-CMMI 2037097) to Dr. Masoud Akbarzadeh. It was also supported by Villanova University Summer Grant Program (USG) to Dr. Joseph Yost. The multi-axis milling, metalwork, and other facilities were supported by Eventscape NY.