Experimental Study on Delaying the Failure Time of In-Service Cables in Trays by Using Fire-Retardant Coatings

Improving the fire resistance of the key cables connected to firefighting and safety equipment is of great importance. Based on the engineering practice of an oil storage company, this study proposes a modification scheme that entails spraying fire-retardant coatings on the outer surface of a cable tray to delay the failure times of the cables in the tray. To verify the effect, 12 specimens were processed using five kinds of fire-retardant coatings and two kinds of fire-resistant cotton to coat the cable tray. The specimens were installed in the vertical fire resistance test furnace. For the ISO 834 standard fire condition, a fire resistance test was carried out on the specimens. The data for the surface temperature and the insulation resistance of the cables in trays were collected, and the fireproof effect was analyzed. The results showed that compared with the control group, the failure time of the cable could be delayed by 1.57–14.86 times, and the thicker the fire-retardant coatings were, the better the fireproof effect was. In general, the fire protection effect of the fire-retardant coating was better than that of the fire-resistant cotton.

Effect of temperature on the bond-slip between I-shaped steel and concrete

This paper presents results from an experimental study on the effect of temperature on bond strength of I-shaped steel and concrete. Eleven concrete encased steel (CES) specimens were tested by home-made fire test furnace to evaluate bond strength at various constant high temperatures (20°C600°C). The test results showed that: (1) the trend of the bond-slip curves at high temperatures were much similar to that at room temperature. Compared with room temperature specimen, the ultimate bond load and the residual bond load of specimens at high temperatures were significantly decreased. The specimens with the higher temperature had the less ultimate bond load and residual bond load. (2) In the descending stage, the P-S curve of the specimens with higher temperatures had more flat slope. The P-S curve of the specimens at the temperatures higher than 250°C had invisible descending stage. The ultimate bond load of the specimen at 600°C left with only about 5% of that at room temperature. (3) The ultimate slippages (i.e. the slippage at the ultimate bond load) of specimens at high temperatures were larger than that at room temperature, and varied from 2 to 5 mm. (4) The calculation formulas of ultimate bond load, ultimate slippage, and residual bond load at different temperatures were presented, the constitutive equations of bond-slip at different temperatures were obtained, which will provide a reference for the fire-resistant design of concrete encased steel columns.

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.