A beam bridge, also known as a girder or stringer, is a simple bridge that supports modern weight requirements. It has columns below it that accommodate the required extra length. A pier or the abutment on the ends of the span supports the beam bridge. There are so many types of beam bridges. Below are some of their pros and cons.
Pros of a beam bridge
1. It is an affordable building option: Since a beam bridge is a simple construction, it has minimum building costs. Using a beam bridge makes it an ideal way to save some cash on infrastructure construction with design simplicity. The bridge provides an alternative to arch and suspension bridges.
2. Faster construction process: A beam bridge typically takes the shortest time possible to construct compared to other types of bridges. The process is much faster in places where material transportation is not a problem, for example, places with good roads. Another factor that makes the construction faster is steel and reinforced concrete, which make the construction process fast.
3. They are helpful in almost any location: All beam bridges perform adequately no matter their location. Although some bridges work better than others depending on their site, the beam design is fundamental in various situations. The bridge is used commonly in highways and railroads
4. Multiple design options: Beam bridges can take different designs. The most common one is side-by-side box rafters and trusses. A beam bridge is not limited to a single span. When constructing, the use of concrete elements improves the strength of the bridge, making these bridges very suitable
5. A beam bridge has multiple material options: For instance, you could use wood products to build a simple bridge for pedestrians. You can also use other materials such as planks, slabs, and steel when making this type of bridge. These materials tend to be inexpensive. Wooden bridges are made in this design to reduce the amount of labor to transport materials to the location.
6. No moments are transferred: Beam bridge does not have arches that facilitate the transfer of moments; hence the design cannot accommodate thrust. Designs with bow-string arches and lenticular trusses are added to the structure to contain the horizontal forces that the bridge must withstand.
7. Beam bridges are highly durable: The beam bridge design has significantly higher durability. The simple nature of the design allows the materials to resist rust, rot, and other environmental damages that may negatively impact the functioning of the bridge.
8. Opposing displacement in every direction: Some beam bridges taking an example of a fixed beam bridge, tend to oppose displacement hence useful in moments of inertia
9. Can retain integrity: Beam bridges can maintain their integrity even during natural disasters such as floods and earthquakes. Since most of them are wood, they are resistant to moisture damage, unlike other types of material.
10. Easy to sustain thermal expansion: An extra beam to the arm of the existing beam of the beam bridge, as in the case of a cantilever beam, helps sustain ground movements and thermal expansion since the beam rests on the arm, giving it that ability.
Cons of a beam bridge
1. Existing span limitations: When using a beam bridge, you only need to cross a specific amount of space because this design requires ongoing pillar support. You may fail to find a single span of more than 250 feet since this option has a higher resistance to bending forces. When multiple you use multiple spans with many pilings, the construction process can go unlimited. Still, the result may not be feasible in communities that experience adverse weather events.
2. Beam bridges can start to sag: A beam bridge has a weakness in that it does provide weight transfer as the traffic crosses on top of the deck. If the bridge receives a consistent weight in its placement on a specific area, the support mechanisms start to buckle as the bridge ages. The sagging gets worse unless maintenance intervention takes place.
3. Do not offer a lot of flexibility: The function of a beam bridge is to provide a safe deck to cross a span and nothing more. Engineers constructing this bridge have limited options when handling challenging atmospheric conditions at the placement location. Severe side winds lower-traffic protection, thereby increasing wear and tear. As a result, the maintenance costs are much higher.
4. High maintenance costs compared to their bridges: Beam bridges are affordable from an initial construction viewpoint. Using steel and concrete in building the bridge helps lower the costs involved, but it is still expensive when you put together bridges and roadways expenses.
5. There are limited placement options: Many beam bridges cover short spans due to the limited piers and pilings necessary to support the bridge. Most of them cover small waterways, highways, and natural obstacles. If you construct a bridge over a navigable waterway, the design of a beam eliminates it as an option of that type of placement.
6. The deck span width is limited: The limitation of the span causes the beam bridge to carry traffic that only provides two lanes of traffic support. If more lanes of traffic are supported, more bridges are built instead of one, and this process will provide unique and challenging infrastructure questions.
7. The cost advantage of a beam bridge can disappear: Beam Bridges are cheap to build, but this may not apply to all communities. When constructing a small and single-span bridge, a beam bridge can be a more expensive design option to build, primarily when you use steel and reinforced concrete.
8. A beam provides only essential support: Beam bridges are not fancy in any way. The objective of the beam is to get one specific done successfully. There are no crucial aesthetic elements of construction in this design of a bridge artwork that is necessary to improve its appearance.
9. There are no built-in supports: Although this kind of design of bridge support only some considerable length, most of them are used for short spans because there are no built-in supports for the bridge.
10. Beam bridges can go through wear and tear: Beam Bridges can undergo a significant amount of wearing and tearing in their lifetime. The bridges usually have a lifespan of fifty years or less. Poorly maintained bridges generally wear out faster hence a decrease in their lifespan. Ongoing maintenance increases the lifespan of a beam bridge, preventing it from wear and tear.