During the 1820s, truss bridges were built in most states in the United States, making them one of the oldest bridges in the United States. Its design makes it ideal to be constructed over areas with unstable ground since it can support an opening while the strength comes from the horizontal and vertical layout pattern on each side.
Trusses, resulting from joined elements that create a series of triangular forms, support the bridge. Early structures consisted of wood and metal materials, with timber being in abundance during those times, making this type economical to build. However, opposing views are still raised on the efficiency and practicality of this structure.
List of Pros of a Truss Bridge
1. Ability to accommodate heavy loads.
One of the qualities of a truss bridge is its capability to support the weight of cars and trucks. Its elements are designed to withstand compression and tension, making it able to bear the maximum of loads. The connected elements of the structure form triangular units which enhance its strength.
2. It is lightweight.
Basically, lesser materials are needed to construct the bridge, thus the reduction in weight.
The series of triangles with equal lengths in the structure are enough to make it rigid unlike having to connect elements to form a square. Moreover, there is only the need connect the elements at their ends with the forces applied at the joints.
3. Construction is convenient.
What makes a truss bridge a preferred structure over other types is its versatility to be built in locations where construction can be difficult such as deep trenches and long span of areas are needed. A truss bridge can be built conveniently to connect between mountains and over railways.
List of Cons of a Truss Bridge
1. It has a weakness to torsion.
Although a truss bridge can carry heavy loads and is known for its strength, the structure has the tendency to twist from torsion forces. During natural disasters like hurricanes and typhoons carrying high strong winds, this bridge type might not be spared from being damaged.
2. Maintenance requires time and expense.
An old truss bridge that has been constructed for a long period of time needs to be maintained for it to last longer and serve its purpose. This makes it harder for engineers to retrofit this type of bridge, given the construction method used when it was built years ago. It also needs meticulous inspection. Considering its size and complexity in design, it can take much time and money to conduct an inspection.
3. It is not spared from buckling and cracking.
Overtime, elements of the bridge can suffer from continuous use and abuse, which can lead to weakness, crumpling and cracking of gusset plates. As the structure is exposed to compressive forces, it can reach a point where its strength is put on the line and the vertical elements are affected which can lead to instability referred to as buckling. On the other hand, after years of use and the volume of cars and heavy trucks on the truss, heat can build up from friction and impact the components. It might not affect the whole bridge but this can weaken the structure.
Conclusion
A truss bridge is still one of the strongest and most durable types of bridge in modern times. It has also been a significant part of transportation and engineering history. And although truss fabrication can be quite expensive today and there are other bridge types constructed all over the world these days, it has managed to maintain its popularity.