A truss bridge is a framework that has a triangulated design and where in trusses are used to support and stabilize the bridge. The elements used are to handle compression, tension and weight of the different types of loads. It was in the 1820s when truss bridges where built in the United States and considered to be one of the oldest types of bridges. Materials used are metal and timber since these are found in abundance during those times.
Also part of what is termed as beam bridge construction, truss bridges gained popularity during the early parts of the Industrial Revolution. As manufacturing and production also increased, there was also an increase in the need of transporting products to consumers. It was also during this time when engineers came up with different designs for this bridge type, from using wood to creating iron models and a combination of both. In the United States and the world, there are numerous truss bridges still in operation. Despite the popularity of truss bridges, there are still advantages and disadvantages associated with idea of using this bridge type.
List of Pros of Truss Bridges
1. Heavy Load Accommodation
Experts say that a truss bridge is a reliable type because of its ability to withstand the weight of heavy loads of the cars and trucks that use it to get to and from a destination. Since it is designed in such a way that its elements can withstand compression and tension, maximum loads from vehicles are easily handled. Also, the strength of truss bridges is supplied by the connected elements of the structure which are triangulated.
2. Ease of Construction
Engineers prefer building truss bridges because these structures have the flexibility to be built in different locations with different depths and width. They can be erected in deep trenches, under water and areas with long spans. Moreover, they can be built with ease in between mountains and even over railways.
The design of truss bridges allows for more rigidity and stability despite the lesser number of materials use. This is because the triangles formed as materials that are connected are stable and the required number of materials is lesser. Unlike in forming a square where four parts need to be joined, a triangle only requires three parts. This will not only result to stability but also being light. Since bridges like these are lightweight, they are also easier to transport and materials can easily be mobilized. With lesser materials needed for construction, lesser weight is to be expected.
With the convenience in construction and the abundance of supply, it will be possible to build truss bridges anywhere. This is very important especially in locations where there are lesser roads, say, in mountainous ranges. A truss bridge can be built to connect to islands or two cities separated by sea. With more bridges constructed, people will be able to move from one place to another, products can be delivered to consumers living in other destinations.
One of advantages of building truss bridges is the availability of jobs for people, from different professions, from engineers to skilled workers. With the construction of more bridges, more manpower will be needed and this can open job opportunities.
List of Cons of Truss Bridges
1. Maintenance Requirements
If a truss bridge has been in existence for decades, it needs to be maintained and checked every now and then which requires time and expenses. Moreover, an old bridge is most likely to be worn and rustic due to its age. As a result, engineers will have a challenging time to retrofit this bridge type especially that construction applied to this structure is different from how bridges are constructed nowadays. Aside from meticulous inspection, it has a complex design and its size can be enormous. For just a simple inspection, it might take months to carry it out as well as require a substantial amount of money for inspection and repair.
2. Torsion Issues
It is true that a truss bridge is able to bear heavy loads from cars and trucks passing through. However, critics also notice that it is not spared from the tendency of twisting from torsion forces. Typhoons and hurricanes are just two of the natural disasters that can affect the structure. These forces of nature can carry strong winds and heavy rains which can damage truss bridges. If this happens, stability and strength will be jeopardized.
3. Buckling and Cracking
In the passing of time, the materials or elements used in the construction of the bridge are exposed to use and abuse. As stated previously, strength of the truss bridge can be put in line and can lead to crumpling as well as cracking of the plates. The bridge is subjected to compressive forces and the vertical elements are also affected which can lead to instability of the bridge. Also, as the number of cars and trucks driving through increases and the frequency of the instances of passing through also increase, friction and impact on the components can result to heat build-up. And although this might not have an effect on the totality of the bridge, this can also weaken the structure.
4. Space Consuming
Perhaps one of the setbacks of building truss bridges is the amount of space it can eat up by the infrastructure. For this reason, other structures will be affected to give way for construction, including converting farm lands and displacing people. Critics argue that this can affect livelihood and the lives of families living the in area.
5. Different Designs
There are numerous designs for truss bridges and all have its advantages disadvantages. The existence of variable designs is part is one of the cons of these bridges. The Warren Truss, a popular truss bridge design uses isosceles triangles. This design allows for distribution of load. However, it can be expensive to build because of more members needed. Also, it is not reliable when it comes to concentrated load.
Truss bridges are still popular and still one of the most durable types of bridges. Despite the emergence of other bridge types, truss bridges remain reliable. On the issue if they have more advantages and disadvantages, perhaps, it depends on the budget and location of where it will be constructed.
Crystal Lombardo is a contributing editor for Vision Launch. Crystal is a seasoned writer and researcher with over 10 years of experience. She has been an editor of three popular blogs that each have had over 500,000 monthly readers.