The risk assessment for road tunnels

The number of tunnels used for transportation purposes around the world is steadily increasing to reduce the number of cars at street level. Given the possibly dramatic consequences of large fires occurring in tunnels, there is a need for assessing the level of risk in these infrastructures. Since the publication of the Directive 2004/54/EC of the European Parliament, risk assessment has become an integral part of tunnel design. Also a great number of road tunnel will be requalified in the next years. A risk assessment tool allows to evaluate design alternatives respect to the safety goals identifying the “best” solution.

Why ARTU

The focus of ARTU is on life safety, so the expected output of analysis is the societal risk (expected number of fatalities per year). ARTU calculates an FN-curve related to the occurrence of a fire, in new and in existing tunnels that are due for renovation.

An example of ARTU output is reported below.

The innovation of ARTU

The innovative aspect of ARTU is that it uses a probabilistic framework in order to evaluate a large number of fire scenarios, and a deterministic approach to describe the interaction between fire products and people involved in the accident. The egress path of each agent in the software is simulated taking into account the environmental conditions (presence of smoke and other people). The effect of fire on each agent is estimated by the FED (Fractional Effective Dose) parameter, allowing a detailed description of damage in terms of life safety.

ARTU validation

Cantene appointed Lund University to perform a validation of the tool. Key and critical factors which may have an impact on the fire development and evacuation conditions were identified. After the literature study, experimental data-sets were chosen along with benchmark simulations conducted with the Fire Dynamics Simulator (FDS). Experimental results, FDS output and hand calculations were compared, by Lund researchers, with ARTU results. The result of the validation process is that overall, ARTU provides conservative results for risk analyses in road tunnels.

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