Trusses are a specific framework that is used in construction projects. When you look at the attic of the average single-family home in the United States, there is an excellent chance that you will see this technology at work.
This framework will consist of using struts, posts, and rafters to support the overall structure. Although the frames can take on virtually any shape, the most common one in use is the triangle. We can use this technology to put a protective roof on a home. It is also useful when a bridge is required to span a specific distance.
The reason why the shape is so useful for building bridges is the fact that when it is placed under stress, the tension or compression created makes the structure stronger. This process makes it possible to support dynamic loads under variable conditions.
Truss bridges are one of the oldest forms of construction used by humanity to cross significant spans. We are still using this design today to allow vehicles the opportunity to pass over rivers, valleys, and other structures safely.
These are the pros and cons of truss bridges to consider when comparing this technology to other methods.
List of the Pros of Truss Bridges
1. Truss bridges are one of the lightest options available to builders.
The most significant advantage of using trusses for bridges is that it allows us to span a considerable distance without creating a massive weight penalty for the structure.
This design makes it possible to install a bridge in places where the volume of the structure impacts the surrounding environment. You can still add reinforcements to this design without creating additional stressors that affect the quality of the span.
Many truss bridges incorporate lightweight metals or small timber lengths to brace the structure against the potential hazards that wind or precipitation would bring. Each part of the structure works to support every other component.
2. Truss bridges can span virtually any distance safely.
Engineers can install this type of bridge almost anywhere in the world today because of the efficiency of its design. Although many truss bridges tend to support smaller spans within transportation networks, the overall design of this bridge makes this a virtually infinite resource for builders. As long as the design of the bridge has enough width and column placement support for the traffic moving above, you could place this design almost anywhere to cover any length successfully.
3. Truss bridges place traffic on top of the structure instead of within it.
Another advantage of using trusses as the foundation of bridge design is that engineers can place the deck on top of the structure instead of incorporating the roadway within it. This process makes it easier to prevent ongoing traffic delays during maintenance efforts while also giving the bridge extra strength because it can transfer the pressure, weight, and momentum throughout the entire structure.
That’s why truss bridges can be built off-site, then installed once the pieces are delivered. You can have the road sections mounted on the framework, which cuts down the overall manufacturing costs of the structure.
4. Truss bridges can be built from multiple materials.
If you look at the average bridge today, then there is a good chance that it is constructed from concrete or metal. Even the concrete bridges use metal rebar as a way to create a firm structure. When using truss bridges, there are several additional material options engineers can use to construct the span that is necessary. If the bridge is for personal use, a wooden support frame is even possible.
Each material has different pros and cons to consider, but it also gives us more options to ponder when creating a framework that meets the needs of the region.
5. Truss bridges are extremely adaptable to changing conditions.
Truss bridges Will often go in places where other design options are impossible to use. The conditions that this design can withstand are quite impressive. There are places where trusses make it possible to have a bridge when it would normally be an impassible span. The versatility that becomes available because of this technology makes it a first-choice option whenever there is a call to expand transportation networks.
6. Truss bridges are one of the most affordable options available.
Truss bridge designs often require fewer materials to complete the structure when compared to other possibilities. Most of the pieces that engineers develop with this option can fit together quickly as the bridge builds outward. This makes it possible to save on design and implementation costs, while also reducing the labor needs of the structure. When the final cost considerations are added together, this bridge option can save some communities over 30% when looking at the final expenses.
7. Truss bridges offer a superior level of strength.
The truss design is useful in any situation where strength is essential to performance because of how the frames distribute weight throughout the entire structure. It also creates a minimal impact on the surrounding ecosystem because of how it naturally incorporates itself to the environment. That’s why it is the preferred choice for high-capacity situations where ongoing traffic needs must receive regular support. It provides consistency (despite the requirements for more maintenance) that other designs cannot offer in the same way.
List of the Cons of Truss Bridges
1. Truss bridges can sometimes become structurally unsound quickly.
The way that trusses distribute weight and pressure can cause premature wear and tear to occur when using this technology for a bridge. That is why shorter distances are usually covered with this option.
When the deck covers a long distance, then the pressure placed on each point becomes greater. Even with frequent monitoring and ongoing maintenance, a full replacement is often necessary faster using this option compared to the other designs that are in use today.
2. Truss bridges require perfect construction to be useful.
The goal of the trusses in this bridge design is to distribute weight evenly along each part of the framework so that every component can share in the work. If this process does not occur because of errors in the manufacturing or installation process, then some of the frames may not ever bear any of the weight coming from the deck. This imbalance can further the issues of premature wear and tear that this bridge option creates.
3. Truss bridges tend to create a substantial outcome.
Trusses can create a lightweight bridge design – in theory. When engineers implement this option to cover a span, the structure tends to be heavier than what other design options would be with the final product. Even when a bridge covers a short span, the trusses used for the design require additional support columns to maintain its effectiveness. If the installation location offers minimal clearance, then there is a strong possibility that the truss design will not work at all.
4. Truss bridges have a lower weight tolerance than other designs.
When you look at how the transportation industry has evolved over the last 500 years, we have gone from a horse and carriage society to one that used railroads and light vehicles. Our modern infrastructure uses heavy trains, semi-trucks, and other cars which continue to increase in size. Although the original truss bridges supported these networks, the load-bearing ratings are struggling to keep up with how vehicles are changing.
On older truss bridges, some drivers must pay attention to the maximum weight rating to prevent damaging the structure, their vehicle, or putting their life at risk. That’s because the design today offers a lower per-capita weight tolerance than other bridge designs.
5. Truss bridges require architectural and engineering specialists to be successful.
Although there are advantages to consider when manufacturing bridge components offsite, there are some disadvantages that can become problematic as well. The framework for this design may be simple, but it requires specialists to attach each component to the structure or fit the deck to its proper moorings. You’ll have fewer general laborers or steelworkers involved in the process, but it will also require the contractor to pay higher wages to those who are working on the project.
Even when there are specialists working on a bridge design like this, all it takes is one small error to change the weight distribution model. That creates another potential issue that can lead to premature wear and tear over time.
6. Truss bridges require a higher level of ongoing maintenance.
Even if none of the other disadvantages of truss bridges become apparent over the lifetime of this structure, the higher levels of support require maintenance personnel to work on the framework more often to maximize its value. There are several additional connections and components in this design that create a higher risk of failure at some point. Every inch of the structure plays a significant role in how the span performs. Routine inspections must look at the wear and tear that happens to prevent a shift in loading where some areas might receive more pressure than others when supporting the weight of the deck.
7. Truss bridges require more width than other designs.
Although there is some flexibility in the design of truss bridges, there are width requirements which must be met for the model to be successful. If you are looking at a lengthy span that the bridge must cross, then this disadvantage can make it impossible for the design to be useful. There are unique spatial needs that truss bridges require before they can be considered for installation at some locations.
The pros and cons of the truss bridge design let us see how past innovations can still create future outcomes for society. As we continue to learn more about the frameworks of support and how modern materials can evolve it, we can limit many of the disadvantages which are found here. That makes it possible to install a bridge for a minimal cost while still benefiting from its significant transportation improvements.
Brandon Miller has a B.A. from the University of Texas at Austin. He is a seasoned writer who has written over one hundred articles, which have been read by over 500,000 people. If you have any comments or concerns about this blog post, then please contact the Green Garage team here.