Full scale 90 and 120 minute fire tests on loaded compositely designed, concrete filled, hot finished structural hollow section columns externally protected by an intumescent coating have confirmed that substantial reductions can be made to the costs of providing an extended fire life to the finished column.
Minimum column size was first established by designing the columns as fully utilised, composite, concrete filled hollow sections, at room temperature. The columns were then protected with Nullifire S605 intumescent coating.
Substantial reductions were made in the intumescent coating dry film thickness by taking full account of the column’s improved ability to absorb heat due to the presence of the concrete core. The performance of the concrete core had been quantified by an earlier series of fire tests performed on a wide ranging set of indicative SHS specimens.
Table 1 compares the revised dry film thickness in microns (µm) of Nullifire S605 needed to provide 60 minutes fire resistance to typical sizes of concrete filled sections with the previous specified coating thickness, which was based simply on the Section factor (Hp/A) of the unfilled hollow section.
Tables 2, 3 and 4 show the reduced coating dry film thickness that can now be used in conjunction with Corus’s hot finished structural hollow sections to EN 10210, filled with a structural grade concrete and designed as composite structural concrete filled sections at room temperature, and protected with Nullifire S605 intumescent coating.