The team began the semester by finishing the RISA model and testing the final model for all possible loading combinations. The final model is an offset cantilever design meaning one end of the bridge is freestanding and the legs are located at staggered positions along the horizontal axis. The final bridge design implements a truss-like structure spanning the length of the bridge on either side allowing for vertical and diagonal supports to be placed along the length of the bridge connecting the top and bottom chords to allow for more support along the length of the bridge. Then laterals connect the north and south sides of the bridge with diagonal lateral supports to help with the sway and defection that the loading the bridge is designed to endure. The bridge is 21 feet long, has 7.5 inches of clearance between from the bottom chords and the ground, has member lengths less than 42 inches long, offset cantilever legs separated by 3 feet, and the bridge is 2 feet 6 inches wide. The final design featured diagonal laterals that would go directly under the top connections to help with the sway and deflection. They spanned from vertical support to the next vertical support on the other side and continued down the span. The bridge featured a truss design to help with the loading to ensure deflection was lowered and went down the length of the bridge from vertical support to vertical support with a lateral going down the lengths of the bridge to ensure the bridge stayed together. All members were made from Grade B A500 steel.
Complete RISA ModellingThe connections for the bridge were made of Gage 11 Grade B A500 steel, and they were all 1/8th inch thick and ranged from 1-5 inches in length and 1-4 inches in width. These were used to connect multiple members at a singular point and had multiple different types of connections made for the bridge and the team used AutoCAD to analyze and dimension the connections to fit the spacing of the members and the area of the bridge members. Through the analysis found in the report the tests and calculations showed that the minimum amount of the loading each connection could sustain needed to be 4 kips as that was the lowest amount of force a single connection could sustain. This is under the notion that if the connection that could sustain the least amount of force can’t sustain the minimum amount of force it could then there would be no point in making it as it would fail. The team went through and calculated that since the max loading the bridge could endure was approximately 2 kips, therefore each connection must have a strength of over 2 kips. The most used connection is the penta-connection as it keeps 5 members together and that is the most frequent type of connection used.
Connections SchematicsThe final modelling of the bridge with connections and each individual member type can be found below.
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