what determines the distancea beam bridge can span
Beam bridge Beam bridges are often only used for relatively short distances because, unlike truss bridges, they have no built in supports. The only supports are provided by piers. The farther apart its supports, the weaker a beam bridge gets. As a result, beam bridges rarely span more than 250 feet (80Â m). This doesn't mean beam bridges aren't used to cross great distances, it only means that a series of beam bridges must be joined together, creating what's known as a continuous span.
Tappan Zee Bridge (2017–present) Tappan Zee Constructors began construction in 2013. The north span officially opened to westbound traffic on August 26, 2017; it also opened to eastbound traffic on October 6, 2017. Tappan Zee Constructors then began demolishing the old bridge. Eastbound traffic will be switched to the south span upon its completion. Both spans are expected to be operational by the end of 2018.[4]