Joe Chapman – 590529 Week 2
This activity allowed us to think about the concepts covered in the previous week, and then to put them into action and properly test different concepts, and push the materials as well as design concepts literally to breaking point. It focused us on the ideas of framing, trusses and bracing, as well as showing the effects of loads on these things.
We decided as a group to form our structure based on the use of triangles as our main design feature. As we saw from the readings in Ching, triangular truss systems give rigidity to a structure, which is important when aiming for a tall construction.
Our construction method took on the form of a system. Ching described a system as an assembly of interrelated or interdependent parts forming a more complex and unified whole. We constructed separate triangular prism truss sections and then combined them together, with additional bracing along the top to improve rigidity. This formed a solid, stable base for our tower to grow from.
From this point we introduced vertical columns into the design to start increasing the height, stabilized by braces along the top. We then continued with the systems approach to the construction by repeating this box like form and gluing it on top.
We used our remaining pieces of balsa wood to finish of the structure by repeating the triangular truss system used for the base, and adding it to the top to maximize the height. As described in Ching, tall buildings are most susceptible to lateral forces, however by creating a wider, braced bottom, and having the tower finish with a slimmer profile, we were able to create a structure that is much more resistant to sideward forces.
We then tested our system by applying static loads at different points and different levels of the tower. Due to the shorter lengths of our balsa wood pieces, they were able to hold a lot more weight than many of the other group’s structures where the pieces were thinner and longer.
It was only when a relatively large amount of weight was placed on the structure that it gave way. However unlike all other groups constructions, instead of failing due to bending under the weight, our structure collapsed due to a direct failure of the material, with it snapping at a point on one of the base triangular trusses, where all the weight on the structure was concentrated. This helped us to understand that the actual design of our structure was quite sound, and it was more a result of the fairly weak nature of balsa wood under loads that caused the collapse.