GFRP rebar used for Electromagnetic Isolation in Miami Metrorail

| By jroberts | In News |

Miami-Dade Transit is nearing completion of the $506 million elevated heavy rail expansion of the Miami Metrorail Airport Link extension connecting the Miami Inter-modal Center at the Miami International Airport to the Earlington Heights Station. A unique aspect of the 2.4 miles of elevated heavy rail construction is the extensive use of Aslan 100 Glass Fiber Reinforced Polymer or GFRP rebar produced by Hughes Brothers Inc of Seward Nebraska, to improve the electrical isolation of high voltages.

The non-conductive and non-corroding GFRP rebar was used as reinforcing in concrete rail plinths and deck bars in both segmental precast and the cast in place concrete decks of the guide way superstructure. Hughes Brothers was a prime supplier to the JV and worked closely with both Odebrecht-Tower-Community JV and the rail contractor, Railworks, to fabricate and furnish the GFRP bars.

In the Miami system, the contact rail provides power to the transit vehicle, and the running rails act as the negative return for the power. Corrosion of the reinforcing steel is a concern in these types of systems due to stray currents. Previously, the reinforcement in the deck of the guide way girders was welded to create a grounded grid. Additionally, reinforcing in the plinth pads was welded to this grid and insulation was provided around the rail fastener anchors inserts for electrical isolation.

Detailing of the plinths and deck bars was optimized to ensure the most economical implementation of GFRP bars and to take advantage of the light weight of the material by prefabricating rebar cages for individual rail plinths. Adjustments for rail height variations around curves as well as pedestal heights complicated the fabrication of the GFRP bar, but according to Jorge Mendoza, Project Executive of Odebrecht-Tower-Community Joint Venture; “Hughes Brothers did a super job in aiding our project team in terms of efficiently detailing the project and logistically furnishing the bar all the way from Nebraska.”

In congested areas and portions of the elevated guide way that passed over major roadways, segmental precast members were launched from piers. In accessible areas, precast U-beams were positioned between piers with a site cast deck incorporating protruding GFRP bars to engage the site cast rail plinths that were completely reinforced with the FRP bars.

The AirportLink will provide Miami residents and visitors with direct Metrorail access to MIA via an Automated People Mover. With this project, Miami-Dade County joins other major cities with rapid transit connections to their airports.