The materials you select for your new pedestrian bridge determine maintenance costs over its lifetime. Making informed decisions during the design process will save money and future frustration while ensuring a sound investment.
A pedestrian bridge consists of four primary parts: abutments, structure, deck, and railing. Keep in mind there is no single best material for pedestrian bridge structures: it depends on the application and environment. In this post, we’ll look at the materials commonly used for each and then compare material properties.
Pedestrian Bridge Components
Each part of a bridge has important considerations with regard to material choice:
- Abutments. Abutments support the bridge and transfer the bridge load into the ground, providing stability. Concrete is generally the material of choice for abutments because of its mix of corrosion resistance, formability, and compression resistance.
- Structure. The structure of the bridge consists of its primary load-carrying members. These are typically made of fiberglass-reinforced polymer (FRP), weathering steel, aluminum, and/or wood.
- Deck. The deck(s) on a bridge form the walking surface for pedestrians. Common bridge decking materials are concrete, FRP, treated lumber, and composite lumber.
- Railing. Railing materials are typically aluminum or steel. For small-scale bridges, such as those in many parks and golf courses, aluminum railings are used most often. This is primarily because of the lower cost of commercially available railing sections as well as aluminum’s high corrosion resistance. Steel railings are typically used for large, high-traffic pedestrian bridges. This is because of steel’s design flexibility, which allows it to coordinate with the project’s aesthetics.
Material Options for Load-Carrying Structures
As you consider the merits of each type of material, keep these additional points in mind:
Weathering steel is a good choice for the structure of a bridge given its high stiffness and strength. What’s more, it offers long usable life in freshwater environments.
FRP is a great choice for remote locations with limited access for large equipment and components. It also holds up very well in saltwater environments and other places where steel corrosion is a problem.
Aluminum offers similar advantages to FRP, but at a higher price point. It is not widely used for this reason.
Treated lumber is widely used for short-span bridges because of its lower cost. Most designers and builders are also very used to working with lumber and have a high comfort level with it. Treated lumber designs typically require regular maintenance and replacement in fewer than 15 years.
Material Options for Decking
Decking material selection should consider user safety and durability in addition to appearance. Here are some important notes about decking material options:
- Concrete and FRP offer similar advantages. Both are solid surfaces that minimize trip hazards, prevent corrosion of the substructure, offer excellent long-term life, and limit the amount of bracing required beneath the deck. FRP, however, is 80 percent lighter than concrete and offers many additional aesthetic choices.
- Treated lumber has been considered a standard decking material for many years, primarily because of its low cost. The downside of this material is that it needs to be replaced every 5 to 10 years due to either section loss (i.e. deterioration) or warping. It can also contribute to tripping or other injury hazards.
- Composite lumber has emerged as a viable replacement for treated lumber because it has a longer lifespan than treated lumber; however, its adoption has been less widespread due to limited aesthetic options.
Do you have a vision in mind for your project but you’re unsure how to execute it? When it comes to pedestrian bridges, Axcess, LLC can help you compare material properties, explore design options, and plan for construction and maintenance. Please give us a call!
