Steel Buildings in Europe

Part 7: Fire Engineering 7 - 42 fire wall protected beam purlin protected column purlin flexible fire protection material continuous purlin protected beam d  200 mm protected column fire wall fire protection purlin Rigid support fire wall purlin protected beam protected column a) Fire wall inserted between the flanges of columns b) Fire wall fixed to one flange of columns Figure 5.18 Design detail near fire walls parallel to portal steel frame If purlins are partially protected, the thickness of fire protection material may be calculated assuming a steel section exposed on four faces for the section factor, a standard fire exposure of one hour and a critical temperature of 500°C. Additional design recommendations for simple portal steel frames In the case of single-storey buildings with simple portal steel frame where the column height/beam span ratio of the frame ( h / l ) is greater than 0,4, the failure mode towards the outside can be avoided by designing the connections between columns and foundation, and the foundation itself, to have sufficient resistance to sustain the vertical loads in the fire situation together with an additional bending moment equal to 20% of the ultimate plastic moment of the column at normal temperature. Fire wall simple portal steel frame simple portal steel frame h L Figure 5.19 Single-storey buildings with simple portal steel frame Examples of fire walls Illustrations of fire walls adopting some of the above recommendations are shown in Figure 5.20. They show clearly that the fire walls were not damaged, despite the collapse of the steel structure.