Architects have increasingly taken steel structures and expressed them in their architectural designs leading to the relatively new defined term in steel design codes and handbooks, namely, Architecturally Exposed Structural Steel (AESS). When meeting building code requirements, fire safety for the primary steel structure requires fire protected steel for virtually all non-industrial-type buildings to give the structure fire resistance (known as passive fire protection). When tubular steel, or Hollow Structural Sections (HSS) are selected for an AESS project it can be passively fire protected by external application of intumescent coatings. (HSS can also achieve passive fire protection by protecting the potentially exposed surfaces with conventional sprayed fire resistive materials or gypsum board, or internally by concrete filling or by water filling the void down the centre of a HSS.) Intumescent coatings are paint-like and give the designer an AESS that is decoratively painted in appearance and also fire protected. The intumescent coating’s chemical composition reacts due to a fire’s heat and expands up to fifty times the applied coating thickness. The expanded ash layer provides an insulating layer between the steel and the heat of the fire. Steel will lose about 50% of its strength at 600o C. To establish the insulating layer’s performance under high temperatures, representative steel test specimens are subjected to standard fire exposures in furnaces fired to follow standard time-temperature curves. Fire test standards, such as ASTM E119 (USA), CAN/ULC-S101 (Canada) and ISO 834 (Europe) have test protocols from which hourly fire resistance ratings are determined for the tested assemblies. This paper overviews the use of intumescent coatings on HSS for two projects where fire resistance ratings were required by the applicable building code.
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