• Question: How do people build bridges without people falling off from trying to connect to the otherside

    Asked by Rohanb on 17 Jul 2021.
    • Photo: Murat Islam

      Murat Islam answered on 5 Jun 2021:

      Hello! Structural engineers would give you a better answer. They first build foundation structures on the ground that is very very strong, and they build a frame over these foundations section by section. If the bringe must cross some water, they may have to build a dam and remove the water first. Because the construction is step by step, and they use big cranes and machines helping them safely move and lift heavy materials, people never fall off.

      Here, you can see how they are building a very large bridge between two small bridges. https://www.youtube.com/watch?v=bJebuNJEe_g

      If you like, you can also try to build your own bridge by watching this video.

      Hope this helps.

    • Photo: Rob Gilbert

      Rob Gilbert answered on 7 Jun 2021:

      Hi Rohan, safety is always the priority when building bridges so we made sure that in the feasibility, options, or design stages we are choosing something that is safe to build.

      The method of building a bridge depends on what it is crossing. Sometimes a short bridge over land can be built as ground level, and then the earth beneath can be removed so traffic can pass under. This method means there is less ‘working at height’ because the ground isn’t too far away from the deck.
      For a bridge that crosses something like a wide river it’s common to build a pier on each side of the riverbank, and the add pieces of bridge deck, one at a time on each pier, until they meet in the middle.

      To stop people falling off the bridge there will be barriers at the edges. Or where this is not possible, people will wear a safety harness that is always attached to something strong. We can also reduce work at height by making as much of the bridge as we can ‘off-site’, or in a safer location. Then either the whole bridge or components of it would be lifted/pushed/floated into position.