1915
Pin-connections are almost completely replaced by riveted connections.
Some bridge companies experiment with bolted connections, but bolts remain
in the minority for many decades. Any pin-connected trusses built after
this date are an anomaly. Also in this year, the Tunkhannock Viaduct is
completed. This was the largest concrete bridge in the world when
completed, a bold engineering expression of confidence gained from
previous years of experimentation, and it marks the beginning of an era
where concrete competes on equal terms with steel as a material for bridge
construction. From this point forward to the present day, almost all
bridges constructed are either steel, concrete, or a combination of both.

