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    FIRE RESISTANT TUNNEL SOLUTIONS

    Why Use Fire-Resistant FRP for Tunnel Applications?

    Tunnels play an essential role in our day-to-day lives due to their importance in the mass transit and utility industries. Commuters in large metropolitan areas depend on tunnels for efficient and lower-cost transportation. However, many are aging, and those built with concrete and steel materials deteriorate in the damp environment. Repairing them is a complex undertaking and can have a significant impact on the lives of public users. For example, the tight spaces and harsh conditions in which they were built make repairs and reinforcement with traditional materials more expensive in terms of time and money. Fortunately, Fiberglass Reinforced Polymer (FRP) is an excellent alternative to conventional tunnel construction materials. 

    There are many advantages to using FRP as a reinforcement material for tunnels, such as: 
    • FireStrong® — The makeup of FRP can also be engineered to suit non-combustible applications. For tunnels, repair panels can be made with a phenolic resin that ensures the final material is non-combustible. This FireStrong quality is essential in confined spaces where the outbreak of fire and smoke could lead to catastrophic consequences
    • Design Flexibility — FRP can be custom molded into various shapes and sizes. This design flexibility can be leveraged to produce reinforcement components that encase damaged tunnel sections or larger panels become the new tunnel structure. This means time and money will not have to be spent entirely on demolishing and rebuilding them
    • Lightweight — Limited access for heavy construction equipment and handling parts means that lightweight FRP parts are the right solution. In many cases, erecting repair parts can be manually carried inside elevators or up and down flights of stairs
    • Non-slip Surface — Non-slip surfaces can be shop-applied to parts to enhance safety for maintenance personnel and emergency evacuation of transit passengers

    Canarsie Landscape

    HOW IS FRP USED IN TUNNELS?

    FRP CAN BE USED FOR MANY PURPOSES IN TUNNEL PROJECTS. FOR EXAMPLE:
    • FRP Reinforcement Panels — Deteriorating concrete tunnel walls results in spalling, which causes concrete pieces to fall on rail tracks. FRP panels are molded to the tunnel's contours, hand-carried into the tunnel, and bolted over the concrete. A great example is the repair of the Canarsie Tunnel between Brooklyn and Manhattan. The FRP solution prevented a 15-month shutdown that would have had disastrous economic effects. Learn more about the Canarsie Tunnel case study
    • FRP Plenum Plates — Ceiling plates provide an air plenum cavity for ventilation. Lightweight FRP plates minimize construction effort and attachment structures
    • FRP Reinforcement Bars — FRP is corrosion resistant, which makes it ideal for rebar used in tunnel structures as they are often exposed to corrosive compounds and other harsh environmental conditions

    Frequently Asked Questions

    • We have found agencies in the areas that must use de-icing chemicals to ensure safety of their passengers to be very receptive. Concrete deterioration is severely shorting the life of the stations to even just 15 years. And the surface spalling creates a tripping hazard. The corrosion resistance of FRP combined with the ease of installation within hectic train schedules is the combination that garners acceptance. Different agencies have different comfort levels, but we find that showing the advantages, limitations and technical details has been the way to convince the agencies.
    • The anchorage of the platform panels to the support piers using bolted clip connections is similar to the clip connection successfully used for 15 years for FRP pedestrian bridge decking. The biggest issue in the past was using neoprene pad as a shim/interface between FRP and steel or concrete in the first few years. Neoprene is not easy to bond in place. Over time some of the neoprene would slide/vibrate out of position. An interface is not needed on steel supports since both the steel and FRP surfaces are relatively smooth. For the FRP Tee panels, we are attaching UHMW PolyEthylene pads to the expansion end of the FRP panel that sits on concrete piers. This provides a low-friction, abrasive-resistive interface.
    • The standard FRP platform panels are combustible when exposed to a fire source. When the source is removed, the FRP is self-extinguishing. The panels have a Class 1 rating per ASTM E-84 for flame spread testing. The flame spread is slow; allowing passengers time to leave the station and meet egress requirements. There are FRP materials that are non-combustible that CA provides for tunnel applications, but the material costs more than the baseline material.
    • The standard panels are for exterior stations only due to the flame spread and smoke generation.
    • Being a relatively new technology, national standards are not yet in place. The requirements are in special provisions. We have a general specification that we can provide in Word format for customization by designers and agencies. We can also provide examples of the specifications from agencies with FRP platforms in use. Key items are having performance-based requirements to avoid a proprietary spec; and having strong manufacturer qualifications to ensure adequate experience.
    • Yes, the grates are FRP. The grates are ADA compliant.
    • We now use stainless steel for the connection clips and the embedded steel inside the FRP panels. In the past, we used galvanized steel clips on the exterior and embedded carbon steel. Since we are selling 100 year life for FRP, it made sense to use stainless. The cost increase is not much.
    • We have sample performance specifications that we provide as a Word document that the Engineer or owner can edit.
    • A small 3/8 inch by ½ inch drip strip is bonded to the bottom of the panel; just back from the edge. When water runs around the edge of the panel, it hits the strip and cannot wick back to the steel support structure.
    All FAQs