Experimental Assessment of Fire Damage to Reinforced Concrete Tunnel Liners

Graduate Student: Nan Hua

Principal Investigators: Negar Elhami-Khorasani, Anthony Tessari

Project Completion Date: July 2021

Extreme fire events in tunnels may have catastrophic consequences, including loss of life, structural damage, and major socioeconomic impacts due to service disruptions. Historically, the collapse of tunnel structures due to fire hazards is rare, but reinforced concrete tunnel liners incur significant damage when exposed to high temperatures and experience irrecoverable residual deformations that could influence the operation and long-term serviceability. Thus, a reliable methodology is needed for the damage assessment of reinforced concrete structures after fire.

Experimental investigation was conducted to study the level of fire damage to the ceiling of a tunnel lining. The test specimens included: (1) 4 large-scale 2,440 mm x 1,830 mm x 300 mm flat reinforced concrete slabs for furnace testing, and (2) 27 small-scale 100 mm x 200 mm concrete cylinder samples for determining the compressive strength (ambient and residual) and moisture content. The effects of three parameters on the response of reinforced concrete slabs during heating and cooling were investigated: (1) concrete composition, varied by the addition of polypropylene fibers that are commonly available in the US market, (2) level of restraint, induced using post-tensioned strands, and (3) fire intensity and duration. The tests showed that a moderate railway tunnel fire could lead to irrecoverable damage in the absence of passive or active fire protection.

This project was supported by CAIT Region 2 UTC Consortium, and the Institute of Bridge Engineering at the University at Buffalo.