ARC 362 Concrete Project

By: Russell Baker & Adam Dubree


For ARC 362, the second undergraduate structures course of three at SIU, we were required to create and test a single-pour, cast-in-place, concrete "bridge" in lieu of a final exam in the spring 2008 semester. This was a fun project that allowed us to get out of the classroom and acquire hands on experience with pouring concrete. Teams of two were to discus and agree upon a concept, create a scale model, perform calculations, and construct and test a concrete slab. The project required the beam/slab to support 8 #6 modular units (bricks) at the end of a 16" cantilever, while simultaneously supporting 16 #6 modular units at the center of the main 30" span. The overall length was to be a minimum of 48", and the slab must evenly rest on a 6" riser step opposite the cantilever. Each modular unit measured 2.5"x4"x8" and must be stacked precisely as seen in the attached pictures.



Material requirements designated the use of no more than one 40lb bag of Quickcrete and 150lb tensile nylon string to simulate rebar reinforcement. The entire structure was to weigh 45lbs or under. Form construction materials included 1/4" foam core, duct tape, plastic wrap, paper clips, and hex nuts. If the slab successfully supported the bricks weight for 30 seconds, and A was earned. If it a completed slab collapsed, the grade was dropped to a B. Five additional points were awarded for each two inches of span or cantilever over the minimum requirement, for the most interesting project structurally, and for the most fun project.


Prior to construction, study models were made from clay, all the bending moment ("strength") calculations were performed in accordance with LRFD design, and moment and shear diagrams were drawn up. Tension and compression components were then analyzed before constructing a digital model of our design. Product specification sheets were also a requirement in the final report submittal. An initial test pour was performed early on to make sure the formwork would support the weight, which in our case, it did not. So modifications were made to the form supports. As predicted by our calculations, our design used every last bit of the concrete perfectly and passed the testing phase with flying colors.