Answer:
Pro
Extremely Strong
Uses materials effectively
Withstands extreme conditions
Roadways built onto the structure
Con
Requires a lot of space
High maintenance costs
They’re heavy
Step-by-step explanation:
PRO
Extremely strong
The structure of interconnecting triangles means that the load-bearing capacity of truss bridges is huge. The structure effectively manages both compression and tension, by spreading out the load from the roadway throughout its intricate structure. This means that no one part of the structure is carrying a disproportionate amount of weight. Sort of a ‘chain is only as strong as its weakest link’ type of situation.
Uses materials effectively
While the truss bridge has many, many linked parts to make up its structure—its use of materials is extremely effective. Materials such as wood, iron, and steel are all utilized to their highest potential, and every piece plays a role. The building of a large truss bridge can be a very economical option when compared to other bridge designs.
Withstands extreme conditions
Where other bridges such as beam and arch bridges may not be a viable option, truss bridges come into their own. They are able to span great lengths, and are often used in precarious locations such as deep ravines between mountaintops. You’ll regularly see truss bridges in use throughout mountainous areas to carry railways.
Roadways built onto the structure
Unlike other bridge designs, the truss bridge is able to carry its roadway on its structure. The load can be carried above (deck truss), along the middle (through truss), or on a bottom truss, which sits below the major truss structure. The options make the truss bridge both versatile and economical to build.
CON
Requires a lot of space
The structure of a truss bridge is, by design, large. The interconnecting triangular components need to be large in order to bear and distribute heavy loads. This means that in certain restricted spaces, the truss bridge may not be the best option.
High maintenance costs
Economies of scale! The truss bridge uses a LOT of parts. Each of these are relatively light, and used effectively within the design, which means that if you’re building a huge truss bridge it is economically sensible. However—the maintenance costs of so many parts can be expensive. A truss bridge, like any load-bearing structure, will require regular and detailed maintenance. So many parts to look after can mean that this is expensive—not to mention time-consuming!
They’re heavy
Because truss bridges are so large, and use a lot of materials, they are heavy. Depending on the landscape supporting the bridge, some reinforcement may be necessary to cope with the weight. There may be other bridge options such as suspension or beam bridges, which might be more suitable if your landscape can’t support a truss bridge.
As one of the oldest styles of ‘modern day’ bridges, the truss has been a trusty go-to design for many an engineer, since the early 19th century. Whether you’re building over steep ravines, crossing vast lakes, or planning a creepy B-grade railway horror movie—there’s a truss bridge to suit your needs.