What is your experience in discussing and convincing clients (DOTs and rail entities) that the design engineer's proposal to use FRP is advantageous when compared to concrete?
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.
Could you provide some information on typical problems & solutions for post-installed anchorage of items after construction?
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.
What is the fire resistance?
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.
How do you spec this on a design-bid-build project? Do you have a special provision?
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.
Were the grates for the scupper also FRP?
Yes, the grates are FRP. The grates are ADA compliant.
What type of corrosion protection is provided for the connection clips that connect to the beams?
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.
How do you prevent water and snow melt from reaching the steel support beams underneath?
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.
