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Our 2018-2019 Bridge

Overall Configuration Reasoning

  • Undertrusses are easier and quicker to construct than overtrusses. Additionally, historically, we have seen that undertrusses perform better at competition due to their quicker construction times.

  • By having the top chord act additionally as a loading rail, we eliminate the need to have two seperate, long members

  • Splitting the trusses into “Upper” and “Lower” halves allows us to maximize the depth of the truss, and will reduce the overall weight (in comparison to if we were to do a shallower mini-truss, similar to last year)

  • The major goal of this year’s bridge was to greatly reduce the overall construction time in comparison to past years’ bridges. As such, we aligned the trusses in such a way that one plate connection can connect 4 members together, thereby satisfying the requirement for all members to be bolted to all connecting members while also greatly reducing the required number of bolted connections.

  • The truss was carried to be ~38o as it is an efficient angle to both provide stability within the truss and allow for the vertical transfer of load, while also satisfying the geometric requirements of the 3.5” long truss members.

  • A horizontal truss was designed at both the non-offset end at at the leg of the shorter end, connecting the two lateral trusses together, to both minimize deflection and prevent the twisting of the main structural trusses.

  • A series of diagonal cross-pieces were installed to prevent major horizontal deflections during the horizontal load test.

Design Provisions for Accelerated Bridge Construction

  • As stated previously, the upper and lower halves of each truss section are bolted together with the same plate connection as the adjacent truss section, which greatly reduces the overall number of bolted connections required. This should greatly reduce our overall construction time.

  • Most of the other connections are either “dovetail” or plug connections, which just require the members to slide together, or are plate connections with pre-welded bolts.

  • Historically, most of our construction time was used to install bolts and nuts and to go back over and re-tighten and confirm all the bolted connections. By reducing the number of bolted connections, and welding the required bolted connections where possible, this should greatly reduce the overall construction time.

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