According to the Tata Steel Europe company, truss bridges offer enhanced stability and strength, and they are lightweight compared to other types of bridges. However, they can be expensive and time consuming to construct. Although the many supporting beams provide rigidity to the structure, truss bridges require careful maintenance to ensure that no vital components become damaged over time.
According to the Tennessee Department of Transportation, truss bridges utilize a superstructure made up of triangular arrangements of girders. These triangles provide strength to the overall bridge structure through tension and compression, spreading the load throughout the construction so that no one beam experiences forces strong enough to damage or destroy it.
Truss bridges became common in the early 20th century due to the manufacturing and technological limitations of the time, notes the Project for Pennsylvania Transportation & Heritage. Since bridges had to be riveted together, the triangular framework helped prevent the joints from becoming overstressed.
Unfortunately, many truss bridges were constructed with lighter vehicles in mind. Modern traffic can be too heavy for older spans. For this reason, many older truss bridges have been replaced with concrete or suspension bridges, and those that still remain often have warning signs listing their maximum weight capacities. Truss bridges still regularly find use in low-traffic areas and occasionally appear as pedestrian bridges.