PCI Big Beam Competition 2020-2021

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Design alternatives

Our team considered I-beams and Box-beams since they have a more effective use of material allowing us to minimize our cost and weight for the competition. The following table shows the decision matrix we used. Below the decision matrix are the 10 different cross sections used in the matrix. The designs varied by changing the width and height of different portions of the cross section as well as the amount of rebar or prestressed strands. The criteria the team used for scoring were cost, weight, and deflection which aligned with the competition scoring. Cost and weight were very similar between the deisgns, so the team gave deflection the highest weight on the matrix. Click here to see the spreadsheet used to create our cross sections.

Final Design

Our final design was an I-beam with a height of 14.5-inches, 4 prestressed strands in the bottom, and 4 bars in the top. Our team used half inch diameter low relaxation strands and #4 bars. The design also contained 44 #4 stirrups spaced 6-inches on center and 27 #4 bars placed horizontally over the strands every 10-inches to help confine them. This design was made after the original design failed early due to bursting stresses. There was not enough clear cover around the strands so the forces caused by them led to the beam failing. This is also why a #4 bar was placed over the strands because it would help prevent a failure due to bursting stresses on the new design. Click here to see the shop drawings for our beam.