4 ms·

It specifically was NOT a cable-stayed bridge. It was a non-redundant truss bridge with a tower and faux stays that contributed nothing to the structural capabi

by hrunt 8y ago

It specifically was NOT a cable-stayed bridge. It was a non-redundant truss bridge with a tower and faux stays that contributed nothing to the structural capabilities of the bridge. The arrangement of the truss structure mimiced the stay angles purely for aesthetics, not for any other reason. The choice to use a single truss structure rather than a more traditional redundant set of trusses was due to the desire for a striking design. Adding the tower or cables would have done nothing to strengthen the bridge. The engineers in the article suggest that the second shorter section of the bridge to be built afterwards may have alleviated some of the stresses on the north truss beam, but the truss itself was unorthodox, so they cannot say anything for certain.

tropo 8y ago
The stays were real. They were needed for hurricanes and large crowds. The worst case would be a marching parade, on just one side, during a hurricane.
- gamblor956 8y ago
  No, the article is pretty clear that the stays were fake, and intended solely to dampen vibrations. They provided no structural support whatsoever.
  - burfog 8y ago
    If it is "to dampen vibrations" then obviously it isn't "fake". Vibrations are serious business; many bridges have collapsed due to vibrations, and many more (Millennium Bridge for example) have had severe trouble. Humans are particularly prone to causing vibrations because humans react to bridge movement in a way that amplifies the movement. Technical description of the bridge from the engineering firm: https://facilities.fiu.edu/projects/BT_904/MCM_FIGG_Proposal_for_FIU_Pedestrian_Bridge_9-30-2015.pdf https://facilities.fiu.edu/projects/BT_904/MCM_FIGG_Proposal... Page 3: "The stay cable pipes increase stiffness for pedestrian loads." Page 18: "The stays and pylon provide the required structural design to meet the pedestrian loads for harmonic conditions of natural frequencies" Page 64: "HORIZONTAL FREQUENCY In the lateral direction, the fundamental frequency of the pedestrian bridge shall be greater than 1.3 hertz. VERTICAL FREQUENCY The fundamental frequency in a vertical mode shall be greater than 3.0 hertz to avoid the first harmonic." Page 65: "The pylon stiffness was designed to provide significant benefit to the overall stiffness of the structure."
    - gamblor956 8y ago
      You're reading from the proposal, which is not the bridge that was built. The bridge that they built did not use the stays as structural elements, and any vibration dampening would have been minimal, i.e., a side-effect of stiffening the bridge rather than the reason for including them.
      - burfog 8y ago
        Got an as-built engineering document which contradicts the engineering proposal document? An article written by a journalist doesn't count. Unless you can find such a document: the stays were structural elements.

by hrunt 8y ago

tropo 8y ago

The stays were real. They were needed for hurricanes and large crowds. The worst case would be a marching parade, on just one side, during a hurricane.

gamblor956 8y ago
No, the article is pretty clear that the stays were fake, and intended solely to dampen vibrations. They provided no structural support whatsoever.
- burfog 8y ago
  If it is "to dampen vibrations" then obviously it isn't "fake". Vibrations are serious business; many bridges have collapsed due to vibrations, and many more (Millennium Bridge for example) have had severe trouble. Humans are particularly prone to causing vibrations because humans react to bridge movement in a way that amplifies the movement. Technical description of the bridge from the engineering firm: https://facilities.fiu.edu/projects/BT_904/MCM_FIGG_Proposal_for_FIU_Pedestrian_Bridge_9-30-2015.pdf https://facilities.fiu.edu/projects/BT_904/MCM_FIGG_Proposal... Page 3: "The stay cable pipes increase stiffness for pedestrian loads." Page 18: "The stays and pylon provide the required structural design to meet the pedestrian loads for harmonic conditions of natural frequencies" Page 64: "HORIZONTAL FREQUENCY In the lateral direction, the fundamental frequency of the pedestrian bridge shall be greater than 1.3 hertz. VERTICAL FREQUENCY The fundamental frequency in a vertical mode shall be greater than 3.0 hertz to avoid the first harmonic." Page 65: "The pylon stiffness was designed to provide significant benefit to the overall stiffness of the structure."
  - gamblor956 8y ago
    You're reading from the proposal, which is not the bridge that was built. The bridge that they built did not use the stays as structural elements, and any vibration dampening would have been minimal, i.e., a side-effect of stiffening the bridge rather than the reason for including them.
    - burfog 8y ago
      Got an as-built engineering document which contradicts the engineering proposal document? An article written by a journalist doesn't count. Unless you can find such a document: the stays were structural elements.