Heating Mechanism of Double Tubular Steel Columns Part 1 Verification using the Real-Scale experiment

The construction methods that exposed the steel tube surface from an aspect of architectural design may be used for columns of steel structures, and the method of double tubular steel columns is also one of them. The double tubular steel column secures the fire resistance performance by making some space outside the steel tube that bears load, and installing the finish steel tube. Generally, this space is filled up with cement mortar or insulation material. However, the part directly exposed to fire heating is the outside steel tube, and since the inside steel tube has the space. Even if the fillers are not used, the temperature of the inside steel tube will not increase rapidly. It is expected that the temperature rise of the inside steel tube is governed by the radiative heat transfer from the heated outside steel tube rather than convective heat transfer from the air of the space. Therefore, if the emissivity on the surface of steel tube is low by fitting of paint etc., the effect that controls the temperature rise of the inside steel tube is expectable. So, in this research, the fire resistance tests of the double tubular steel column which galvanized the outside steel tube are carried out. The temperature rise of each part of the member that the heat-resistant paint with low emissivity was applied on the perimeter surface of the inside steel tube, is compared with the temperature rise of each part of the steel that is not applied, and the influence that contributes to improvement in fire resistance performance is considered. In addition, Tokyo University of Science has applied for the patent about the fire-resistant construction method of the double tubular steel column with such heat-resistant paint.