Why don’t bridges crack under the weight of all the cars and people? I did an experiment at a science museum and you

Question: Why don't bridges crack under the weight of all the cars and people? I did an experiment at a science museum and you built a bridge but it was easily knocked down.
- Keywords:
  bridge,
  car,
  crack,
  easily,
  weight
Asked by rebecca.leyland to Huma, Jack, Lucy, Miranda, Peter on 17 Nov 2016.
- Miranda Bane answered on 17 Nov 2016:
  
  That’s a good question. You need to ask an engineer about this. I’m not sure but it’s to do with weight distribution and tension. Engineers can. Work out how to build strong bridges using maths.
- Peter Boorman answered on 18 Nov 2016:
  
  Hi Rebecca,
  
  Great question! This can depend on the shapes used to assemble the materials used to build the bridges. For example, the strongest structure of shape is the triangle!
  
  Peter

Question: Why don't bridges crack under the weight of all the cars and people? I did an experiment at a science museum and you built a bridge but it was easily knocked down.