Project objectives

This project aims to propose a design framework for ensuring self-extinction based on a quantitative analysis of critical mechanisms that may prevent this phenomenon, including extended exposure of timber surfaces, char fall-off, and encapsulation failure.

The framework is intended to be validated in a broader project using an experimental campaign based on large-scale compartment tests where the different failure modes can be isolated. The large-scale campaign explores critical conditions based on a parametrisation of the duration of the fire. The research will build a series of six to ten Cross-Laminated Timber (CLT) compartments that will be tested under fire conditions during 2019 and 2020.

Four different stages are designed to evaluate self-extinguishment by isolating the complexities of (1) ratio of exposed surface, (2) encapsulation failure and (3) char fall-off:

Stage 1: Baseline tests & encapsulation failure [completed]

Stage 1 aims at developing a characterisation of the fire dynamics in a compartment with no combustible linings and investigating the criterion for encapsulation failure.

This stage consists of two tests in which the CLT is completely encapsulated and the duration of the fire is varied. The intent of this stage is to demonstrate the principles of the methodology in which the duration of the fire can be parametrised so that failure can be induced or prevented. In this case, the failure mechanism relates to the plasterboard as no CLT surfaces are exposed. The baseline tests provide a characterisation of the thermal conditions induced by the compartment geometry and the fire scenario with non-combustible linings.

  • Test 1.1 (no encapsulation failure) - Completed.
  • Test 1.2 (encapsulation failure) - Completed.

Stage 2: Char fall-off tests [completed]

Stage 2 aims at investigating the criterion for char fall-off, when the encapsulation failure is prevented.

This stage consists of at least two tests in which the ceiling and a lateral wall are exposed, and the rest of the internal surfaces are encapsulated with a robust system. Based on previous research, this configuration leads to extinction if no char fall-off or encapsulation failure is attained. The intent of these tests is to induce char fall-off before encapsulation failure occurs.

  • Test 2.1 (self-extinguishment achieved) - Completed
  • Test 2.2 (char fall-off and compartmentation failure) - Completed.

Stage 3: Ratio of exposed timber tests

Stage 3 aims at investigating the ratio of exposed surfaces and ventilation that inhibit self-extinguishment to be achieved, when both char fall-off and encapsulation failure are prevented.

This stage consists of at least one test in which more than two surfaces of CLT are exposed, and tested for shorter time scales than char fall-off and encapsulation failure. The fuel load will be the same as Test 2.1. These tests provide validation data points in which an energy balance can be solved, and where extinction is only dependent upon the thermal feedback and not other complexities.

  • Test 3.1 - Scheduled in August 2020.

Stage 4: Effect of fuel nature

Stage 2 aims at investigating the effect of fuel nature on the fire dynamics that affect the occurrence of self-extinguishment in CLT compartments.

This stage consists of at least a test in which the ceiling and a lateral wall are exposed; the rest of the internal surfaces are encapsulated. Based on previous research, this configuration leads to extinction if no char fall-off or encapsulation failure is attained. The fuel load density will be the same as Test 2.1, but using a wood crib. The intent of these tests is to compare the outcomes of the test with Test 2.1.

  • Test 4.1 - Scheduled in October 2020.