Physics of bridges

The architectural achievement of bridges is contributed to the Romans.
2000 years ago the Romans were building bridges stretching over ravines, rivers, and gorges.The most remarkable thing about the bridges built by the Romans is that they built bridges across rivers without any rocks or islands emerging to carry the piers. Although the romans were the pioneers in building bridges, it wasn't until the industrial revolution brought about iron smelting that we were able to build bridges that were not only strong but lightweight. This report gives a brief introduction to types of bridges and problems faced with engineering them.