A bridge railing system’s primary function is to provide public safety along the length and edges of the bridge. It includes redirecting errant vehicles back onto the roadway without posing a safety hazard when struck, as well as ensuring bicyclist and pedestrian safety.
Even though railing systems do not provide structural strength to bridges in general, they must be crashworthy. As a result, bridge railing is stiffer than standard highway railing and more rigid than flexible highway railing.
Because it provides a gradual change in the hardness of the two railing systems, a transition railing is used to connect the two railing structures. Changes in vehicle size and power have resulted in railing design and requirements. The AASHTO Manual for Assessing Safety Hardware (MASH) is the most recent standard for crash testing devices for use on the National Highway System.
It involves redirecting errant vehicles back onto the roadway without posing a public health hazard when struck and ensuring bicyclists’ and pedestrians’ safety.
Although railing systems do not provide structural strength to the bridge, they must be crashworthy. However, much of the existing bridge railing does not meet current code requirements because it was designed for the standards in place at the time of construction.
Because it is allowed that replacing all such railing would be a significant expense, agencies often allow it to remain in place until it needs to be replaced. The bridge still has a reasonable service life remaining, and repair may be an option.
Railings come in various shapes and sizes, and they are used all over the country. The railing is chosen based on service level requirements such as design speed, average daily traffic volumes, the number of trucks using the route, and site geometry.
Other factors, such as functional and aesthetic considerations, influence the railing choice to be used. Bridge railings, Transitions, Approach guardrails, and Approach guardrail ends are the four basic railing systems at bridges and approaches.
These four basic components are intended to meet agency standards for acceptable heights, materials, strengths, and geometric features.
Different Types of Bridge Railing
1. Steel Bridge Railing
Steel railings are available in various cross-sections and designs. A tubular rail system is the most common type of steel bridge rail. Railings for concrete curbs or barrier walls are built separately.
Architectural steel railings are commonly used in low-traffic areas and for pedestrians. Bridges with architectural significance are not bulky and heavy in design, and they use decorative railings without jeopardizing pedestrian safety.
2. Concrete Bridge Railing
Concrete railings are attached to the deck slab to make a vehicle barrier. Concrete railings are the best option for urban areas or bridges carrying heavy truck loads. Concrete railings have a high initial construction cost.
In some cases, large concrete railings can obstruct a clear view of the road. The construction budget, bridge deck material, and required state determine the railing dimensions and construction.
3. W-Beam Bridge Railings
Consider W-Beam railing for smaller bridges or roads with less traffic. This system is typically 27 inches from the top of the bridge to the pavement and is attached to steel posts or truss girders.
The W-Beam is a basic steel railing system that increases strength. The Three Beam, like the W-Beam, is a steel railing that works best in areas with high traffic flow.
Pedestrian and steel railings completed with paint coatings or galvanization. Steel railing system specifications differ by state due to their popularity.
4. Thrie Beam Bridge Railings
Thrie beams are high-strength guard rail systems for highways, particularly on sharp curves and slopes. Unlike W-beams, three-beam rail has a three-wave cross-sectional design and high tensile and anti-corrosion properties.
The impact of out-of-control vehicles can be absorbed by three-beam rail systems, guiding them to a safer stop. These railing systems offer superior performance and versatility.
Conclusion
Preventive maintenance is the process of preventing deterioration of the railing system caused by moisture, de-icing chemicals, traffic vibration, and the environment.
Sometimes materials have flaws from the start, such as thin spots of galvanizing on steel or cracks in concrete caused by improper curing when poured, which can lead to premature failure.
Preventative maintenance aims to slow the failure process as much as possible by employing best-practice techniques and materials. This section describes some methods for providing such maintenance; it is not exhaustive.
Before working on any bridge railing, determine the extent of maintenance and supplies needed, as well as what signs and traffic controls are required.