3 ms·

Maybe because it's a pedestrian bridge? Cars are way too heavier (and you usually have 4 lanes)

• wiredfool 6y ago
  Cars are lighter than people, because people pack much more tightly than cars do. People have a design load in the 100psf range, cars are about half that. (Source - I designed a pedestrian bridge in Seattle before leaving civil engineering)
  • ravel-bar-foo 6y ago
    Is it also more ornerous to control for oscillations in pedestrian bridges? Does that require extra structure, or just tuning?
    • wiredfool 6y ago
      Yes and no. It's certainly something to think about when you have an 'interesting' design that pushes the limits somewhere, and pedestrian bridges often are have that sort of arty component. Or, you don't and it's embarrassing if there's a resonance in the 1-2 second range. Most road bridges just aren't that interesting. They're a concrete slab on a girder, either steel or precast, depending on your local construction environment. (As my bridge wasn't structurally terribly interesting in the end, the biggest issues were clearance with the railroad below while fitting into the height profile we needed for the surface, given the 100yr old elevated structure we were connecting to. That and the extremely low quality soils at the site)