The LWF Blog

Fire Engineering for Healthcare Premises – Structural Fire Protection – Part 19

January 25, 2021 12:27 pm

In LWF’s blog series for healthcare professionals, our aim is to give information on best practice of fire safety in hospitals and other healthcare premises. In part 18 of Fire Engineering for Healthcare Premises, LWF began to look at the provision of structural fire protection. In part 19, we consider time-temperature curves and parametric time-temperature curves and their role in structural fire protection.

Time-temperature curves are mathematical formulas that regulate the temperature in a test furnace as a function of time. Their function is to try to assess and compare the different behaviours of building materials in the same fire scenario.

In the majority of situations, fire-resistance time is not related to the time available for escape from the building, or area of the building, in the case of many healthcare venues using progressive horizontal evacuation procedures.

Standard curves do not take account of fire load density, compartment size or ventilation, all of which have a very great bearing on the size of a fire and the rate of growth.

Time-temperature curves are a feature of standard test methods and do not necessarily provide data which can be used in a performance-based design.

In the case of parametric time-temperature curves, they are used for structural fire design purposes and developed for small and medium compartment fires. The method is reasonably precise in use, to estimate the temperature history of a fully-developed compartment fire. They relate, in the main, to cellulosic (wood-based) fires, rather than polymeric (synthetic organic materials and plastics).

Parametric time-temperature curves are only valid for compartment of moderate size (~100 m2 floor area, 4 m ceiling height) and a limited range of ventilation conditions.

Fire load in a given area is a key parameter in establishing the duration of a fire and its severity. However, fire load alone cannot determine the heat release rate (HRR); the nature of the material of the fire load, e.g. thin wall linings or solid blocks, will also be important.

In Part 20 of LWF’s blog series, LWF will discuss time-equivalent exposure and structural modelling. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.

Lawrence Webster Forrest has been working with their clients for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact LWF on freephone 0800 410 1130.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.

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