Fire testing options for the Port of Miami Tunnel

Fire testing laboratory

The usual practice to conduct project specific fire tests for tunnels is to have segments or slabs sent from the project to an accredited fire testing laboratory. Project specific requirements such as time-temperature curve, restraint, realistic loadings etc. will be applied during a fire test. The advantage of this approach is that the exact concrete mix design and geometry are taken into account during such as test as the concrete specimen originates from the job site. Another advantage is that the full system is fire tested at once including all the system components such as anchors, anchors spacing, mesh for spray systems, gaps, joints etc.

For spalling tests on pre-cast segments, however, the disadvantage is that one may be over estimating the thickness. The fact that no spalling has occurred during a fire test using a certain thickness, does not say anything about the accuracy of the chosen thickness to prevent spalling. A thinner thermal barrier may have provided sufficient thermal protection but that cannot be concluded from just one test, so another test will have to be conducted. As per the 2008 edition, NFPA 502 introduced the RWS fire testing procedure. At that time, the US based fire testing laboratories were not familiar with the RWS testing regime amongst other factors such as. The furnace lining, the burner capacity, and the adaption of furnace software to be able to run RWS type time-temperature curves. To the best of the authors knowledge, up until the date of this publication there is no accredited fire testing labs in the US that can run RWS fires for tunnel linings. However, the existing accredited labs will aim to comply with RWS testing requirements in the near future.

To mitigate this situation, the Port Of Miami Tunnel main contractor could have shipped 5 segments to Europe for fire testing purposes at approximately 20,000 lbs (9,070 kg) each. This would have resulted in substantial transportation costs.

As a result of the above, the Port Of Miami Tunnel main contractor commissioned Efectis The Netherlands to come up with an innovative solution, which resulted in the use of the mobile furnace.