Pedestrian Bridge | Portfolio

Objective: To design a safe and cost effective streel truss bridge for pedestrians across lake Ontario.

Criteria and Constraints:

Must be 4 meters wide and span 150 meters.
Must have a factor of safety of 2 for tension members and 3 for compression.
Affordability: cheaper is better.
Aesthetics: should be visually appealling

Iterative Process:

The project began with each of the group members conducting individual research on the various types of truss bridges. Afterwards, we met up and decided on a relatively strong but cheap arched design:

Unfortunately, after attemping to calculate the forces in the members for several hours, it was deemed that the structure was statically indeterminate, and uncalculatable with the level of knowledge we had at that point.

We changed to a more simple Pratt Truss design, but attempted various modifications in order to lower the maximum forces.

The final design that was chosen was a Pratt Truss with a parabolic top, which helped spread the forces more evenly:

Pedestrian Bridge Design

Self-Reflection:

The key lesson learned in this project was the importance of feasibility assements early on. We would have saved many hours of work if we had known earlier that the first bridge design was statically indeterminant and unsolvable without taking into account the deformations and flexibility of the material.