Last week we constructed an unreinforced beam and a tension-reinforced beam model and calculated their load capacity for shear and bending force to overburden and clearly understand their difference. After we produced two concept model beams from plaster gypsum, we tested them separately to failure under 3 point bending. Then we made a report from test results and we compared calculations and test results. (It was a group work, I would like to thank my group mate for contributing to this assignment…)
Construction Steps for Model
Formworks prepared from hard cardboard which has 0.5m length, 0.05m depth and width. Then it was covered with a plastic bag so that it would stick into the plaster gypsum. The sides were glued with silicone for the gypsum mixture did not leak, and one formwork was threaded to pass through a copper wire for tension-reinforced one. As a second stage, we preapared our models from plaster gypsum by mixing water. The mixture we prepared for unreinforced was a bit lighter according the other mixture. Because before we cast it into second formwork, we gave a break for casting into first formwork. Meanwhile, our mixture became darker and harden. After we casted the mold, we waited for the dryings and we left the molds the next morning.
The calculations varied greatly according to being reinforced or not. As for the accuracy of the calculations, they were done with existing datas indepently from our point of view. However the result of the experiment did not match with the calculations . This situation may be affected by the tension strength of the pilaster with respect to its density and the proportions of the mold and the water combination.
If the dimensions of the beam were smaller then the calculations of the unreinforced beam would be positive value therefore it would seem as if it can carry its own weight and the applied load. Also the type of the reinforcement change the beam’s strength and resistance to break down. The greater the yielding or rupture strength of reinforcement the stronger the beam.