What is the strongest kind of bridge?
This question sometimes appears as a school project which is to be solved by building models. If you look in a list of long bridge spans you will find that all spans of greater than 890 m are suspension spans. Above 890 m, the given question of the strongest has no meaning, because no other kind of bridge exists. Clearly, other types could be made with spans above 890 m, but they would probably be very expensive, and their load carrying capacity would probably be small. It is very unlikely that a cantilever span will ever be made longer than that of the Quebec bridge, which is 550 m long. In fact, for any type of construction, there is a maximal span that can only just hold up, even with no load. The question of longest spans is discussed in another page, and use of models is discussed in the page about model bridges. Whatever the longest possible spans are, we can see that there is a range for which only suspension bridges can exist, and below that there is another range in which cabl