At the APT conference last week, I was one of the judges in the Student Design-Build Competition run by the Preservation Engineering Technical Committee. The most important thing to say on that topic is that, as in previous years, I was greatly impressed by the effort, thought, and creativity that the students brought to the competition.
The construction and load-testing of models at the conference is the showiest part of the competition, but it’s actually a small portion of the grading. Most of their grades comes from the students’ work in researching and analyzing a historic structure, constructing and testing a larger model at their schools, and answering questions regarding preservation engineering. I want to emphasize that failure of the models during the conference load test is expected, and has little on the overall grade.
The picture above is the model arch built by the team from the University of Nebraska at Lincoln. The student on the left was finishing adding a second concrete block to each abutment, to reinforce them for the test. Here’s the test:
The arch block just above the left abutment slides out, precipitating the failure. As you can see in both the still picture and the beginning of the video, that end of the arch was a bit misaligned from the beginning, which was due to the method used to construct the arch. There was temporary wood centering used, but it had some problems and the arch blocks had to be lifted off it to complete the construction. The entire experience is supposed to be a learning experience for the students, but I felt that the failure of the centering to properly help in construction was perhaps the most true-to-life part of this team’s work.
Sliding failures of arches are rare in real life, but absolutely do occur. The video is one of the cleanest illustrations of what they look like that you’ll see.
