Fire-resistance Rating of Square Steel Tubes and Concrete-filled Square Steel Tubular Columns Protected with Ultra-thin Fire-retardant Coating
To promote and criterionize the application of ultra-thin the fireproof coating s to building structures, four concrete-filled square steel tubular (CFSST) pillars as well as two square steel tubes, each protected along with ultra-thin the fireproof coating , were subjected to full-scale fire tests to investigate their fireproof level on the basis of the ISO 834 criterion time�degrees curve. Test results revealed not only the temperature variation characteristics of specimens suffered from inconsistent fire exposure, but also effects of the steel ratio of the test specimen and the number of fire-exposed sides on the fire-refractory level of the test specimen. Test results demonstrated that when protected with an ultra-thin the fireproof coating , the heating rate of the specimens was considerably lower than that of the test furnace, suggesting that the ultra-thin the fireproof coating exhibits good thermal insulation performance. The test results were compared with China�s current criterions for the fire-refractory level of square steel tubes and CFSST pillars, indicating that the criterions would lead to a relatively conservative fire-safe design for four-side fire exposure.