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Building fire resistance rating (FRR),
Fire resistance is the ability of a passive fire protection system or material to withstand a standard fire resistance test.
On the other hand, Fire Resistance Rating (FRR) is the time in minutes
or hours that building materials or assemblies have withstood standard exposure to fire, under specified test conditions.
Characteristics of Fire Resistance Ratings (FRR)
FRR is a measure of the fire resistance of a material or assembly,
determined by performing standardized fire tests and calculations.
There is also a Fire Rating Level (FRL),
which is defined as the test result obtained after a fire resistance test has been carried out.
Although FRR and FRL are used interchangeably,
FRR is the required design fire resistance value specified by the fire design engineer.
While the latter is the actual test value achieved after performing the test.
The FRR for building materials or systems is specified by ASTM E119 or in accordance with Section 703.3.
Where the test sample is subjected to rigorous testing under controlled conditions to infer the corresponding FRR.
These exposure conditions may not match the real-world environments found in the buildings.
The fire resistance rating of a building element depends on the following factors:
- FRL or product test results.
- The type of building material used to make the item.
- The element’s location and proximity to other building elements during a fire, for example, could be floors, ceilings, columns, walls, or beams.
- Presence of non-combustible components near the building element.
How is FRR measured?
In order to determine the fire resistance ratings of materials within hours,
fire sets are installed in a propane gas furnace and its temperature is controlled,
The temperature is increased over a specified period of time in accordance with the standards specified in ASTM E119 “Materials Standard”
This relationship between time and temperature is called the standard temperature-time curve.
Fire ratings are also calculated based on the time it takes for a particular material or structure to fail during a fire.
It is measured from the time the component failure occurs, which does not necessarily mean that the component is destroyed at that point.
The FRR of a substance is measured based on three criteria:
- Structural sufficiency: This is a test of stability where the material continues to bear loads for the duration of the test.
- Integrity: This stage measures the ability of the material to remain intact without cracks when it catches fire.
- Insulation: This stage measures the material’s ability to slow the spread of heat from one side to the other.
Suppose the design requirement for a material or system is a FRR of 90.
In this case, the material must resist fire in three ways – stability, safety and insulation, each for 90 minutes.
After the test is carried out, the FRL rating is represented by three numbers giving the time in minutes for each criterion,
i.e. stability, safety and insulation, in the following formula _ / _ / _,
For example, FRL with a value of 90/90/90.
If no FRL value is obtained, the standards with a lower value are refined to obtain a higher fire resistance rating.
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