Like any other bridge construction, footbridge construction should be long enough to cross the below obstacle and high enough to allow this obstacle function.
Building a footbridge is usually a considerable undertaking, particularly for
communities, and it is essential to make sure that it is really needed and is a top priority and commitment for the communities involved. Since it is going to be part of the landscape, more modern and aesthetic footbridge designs are becoming more common in the last decades.
2. Basic Requirements
Footbridges must be long enough to clear the obstacle underneath which is to be crossed and high enough not to interfere with the below obstacle. Footbridges are designed for pedestrians therefore there is no necessity for a gentle horizontal alignment as it was required for the train or highway bridges. Structural continuity is not a primary concern in the design.
Footbridges have a narrower path compared to the highway or railway bridges. Also they require smaller loads which makes them lighter steel structures.
They require accessories such as access ramps, stairs and handrails.
The flooring of the steel foot bridges are often wooden or composite. For wood floors, the timbers are placed across the steel girders. For composite floors, studs are used to transfer the load between the steel beams and the concrete.
For an example, please check our past truss footbridge projects.
3. Footbridge Types
3.1. Truss Type Footbridges
Trusses offer a light and economical form of construction, particularly when the span is large. The members of the steel trusses are significantly smaller compared to the beam type footbridges. Both hollow sections and hot rolled sections can be used for these bridges.
Figure 1 : Truss Type Footbridge
Truss elements of the bridge either welded to each other in the workshop or delivered to the site to be connected to the other segments or each truss member can be joined on the site with bolts. This decision is up to the site conditions, lifting availability, availability of the transportation.
Truss type bridges are often lighter than the steel beams due to their truss type structure but their fabrication and transportation costs might be higher.
3.2 Beam Type Footbridges
Beam Type footbridges are usually the simplest method of footbridge construction. They use several welded or hot rolled main girders to achieve stability and resilience.
Figure 2 : Beam Type Footbridge
Beam bridges are often only used for relatively short distances because, unlike truss bridges, they have no built in supports.
Both I beams and box sections can be used to build beam footbridges.
3.3 Temporary Footbridges
For emergency or temporary situations, temporary footbridges are designed with a modular structure to assemble and disassemble in a very short period of time. Their modular structure enables to cover various spans making them a versatile solution for immediate action.
Figure 3 : Modular Footbridge
Novelty Steel has designed and constructed temporary footbridges incorporated with stairs.
It is becoming a more common requirement for footbridges to be ‘landmark structures’. Therefore, the design of the footbridge structure is met with more attention than usual.
Many steel contractors are able to provide design and build service, using methods and details of construction developed to suit their particular fabrication facilities and expertise. However for advanced cases, a specialized engineering firm might be required to involve to deliver the ideal solution for the client requirements.