THICKNESS DETERMINATION FOR SPRAY-APPLIED FIRE RESISTIVE MATERIALS

摘要

The procedure demonstrated in Example 1 is the correct process for determining the spray-applied fire resistive material thickness when a higher rating on the beams in the assembly is not required. The procedure demonstrated in Example 3 is appropriate when substituting beams with a higher rating in an assembly with a lesser rating.Using data from existing UL tests to determine the correct thickness of spray-applied fire resistive material requires the correct assessment of thermal restraint (RESTRAINED) and a basic understanding of ASTM E119 test procedures. The data reported in a single UL test may include variations in slab thickness, differing deck depths, lightweight and normal weight concrete, fluted and/or cellular deck, etc. then, thickness data is provided for multiple fire durations and differing conditions of restraint for both the assembly and the test beam. The sheer volume of information available makes the calculation of the correct thickness of spray-applied fire resistive material complex. A frequent response to dealing with the complexity is to take a conservative approach and assume the assembly to be thermally unrestrained and to use the spray-applied fire resistive material thickness associated with an unrestrained beam. If this excessive approach were used in Example 1 above, a two hour rated assembly with two-hour beams, the spray-applied fire resistive material would increase from 0.35 board ft/ft~2 to 0.70 board ft/ft~2. The fiber spray-applied fire resistive material represented by UL D902 has an in-place cost in the range of 0.57 dollars to 0.85 dollars per board foot. Thus, an unnecessary cost of between 0.20 dollars and 0.30 dollars per ft~2 of building area is incurred by the taking the conservative approach.