What are the three main criteria for determining fire resistance failure?

Failure is determined by loss of Stability (load-bearing capacity), Integrity (crack formation allowing flames through), or Insulation (temperature on the safe side exceeding limits).

What is the acceptable temperature rise on the unexposed side of a wall or floor?

The temperature rise on the unexposed face should not exceed an average of 140°C or a maximum of 180°C at any single point.

Does a column have an insulation or integrity criteria in fire testing?

No, for fully exposed load-bearing columns and beams, only the 'Stability' criterion (ability to carry the test load without collapsing) applies.

IS 3809

: 1979

Fire resistance test for structures

CurrentSpecializedTesting MethodFire Safety · Fire Safety

Download PDF BIS Portal Google

This standard lays down the testing method for determining the fire resistance of structural elements such as walls, columns, floors, and beams. It defines the standard temperature-time curve, the loading required during the test, and the exact criteria for structural failure based on stability, integrity, and insulation.

Fire resistance test for structures

Quick Reference Values

Average temperature rise limit on unexposed face140 °C

Maximum temperature rise limit at any single point on unexposed face180 °C

Standard furnace temperature at 30 minutes842 °C

Standard furnace temperature at 60 minutes925 °C

Standard furnace temperature at 120 minutes1049 °C

Standard furnace temperature at 240 minutes1153 °C

Key Formulas

T - T0 = 345 log10(8t + 1) — Standard temperature-time relationship where t is time in minutes

Practical Notes

Failure in a fire test is determined by three criteria: Stability (structural collapse), Integrity (passage of flames or hot gases), and Insulation (excessive temperature rise on the unexposed face).

Structural elements must be tested while bearing their full characteristic design load to accurately simulate real-world stress under fire conditions.