Steel Buildings in Europe

Part 7: Fire Engineering 7 - 20 g  is the gas temperature [°C] Figure 5.5 gives expressions to calculate the section factor of protected steel members. A m /V= (P-b) / A s b A m /V= (2h+b) / A s A m /V= 2(2+b) / A s A m /V= P / A s h b b h P : perimeter ; A s : cross-section area Figure 5.5 Example of section factor for insulated steel members It is important to note that thermal characteristics of fire protection materials are usually determined from fire tests performed under standard fire conditions. Consequently, referring to thermal actions based on natural fires, the use of Equation (8) for the fire design situation of protected steel members should be handled with some caution. The calculation should be performed only if appropriate data are available or if it can be shown that fire conditions have no significant effects on thermal characteristics and integrity of fire protection materials. Nevertheless, it is commonly assumed that thermal properties of an insulation material can be used under natural fire conditions when the temperatures of hot gases remain lower than the maximum temperature reached during the standard fire test for the insulation material (For example, about 1100°C for 4 hours of the standard temperature-time curve). The material properties given in Table 5.2 may be used as a first approximation to calculate heating of protected steel members. These average values are derived from fire tests by material manufacturers.