Your idea as a teacher to teach your students practical bridge building using a 3D pen is fascinating and innovative in its own way. However, your method of testing by applying a point load at the center of the span does not align with the methodologies for testing the load-bearing capacity of bridges and needs to be changed. As a structural engineer, I can easily draw a structure that, with relatively low weight, would bear significantly greater loads than these bridges built by students. However, such a structure cannot be called a bridge in any case, but rather a beam subjected to a point load in the middle of its span. It's also important to remember that trusses can only be loaded at the nodes; otherwise, it simply cannot be said that the structure is working as a truss. Regardless, good luck with the development of your research and teaching program for students!
Your idea as a teacher to teach your students practical bridge building using a 3D pen is fascinating and innovative in its own way. However, your method of testing by applying a point load at the center of the span does not align with the methodologies for testing the load-bearing capacity of bridges and needs to be changed. As a structural engineer, I can easily draw a structure that, with relatively low weight, would bear significantly greater loads than these bridges built by students. However, such a structure cannot be called a bridge in any case, but rather a beam subjected to a point load in the middle of its span. It's also important to remember that trusses can only be loaded at the nodes; otherwise, it simply cannot be said that the structure is working as a truss. Regardless, good luck with the development of your research and teaching program for students!