Han, Zhao, Yang and Feng 2003
This paper includes an experimental study of hollow structural steel (HSS) columns filled with concrete, that are exposed to fire. HSS members filled with concrete increases the load bearing capacity, and increases the fire resistance as compared to steel tubular columns with no filling.
Experimental Study, Results, and Discussion
Thirteen Specimens were prepared which consisted of eight concrete-filled HSS columns with fire protection, and five without fire protection. The main parameters with diameter, tube thickness, fire protection coating thickness, and eccentricity. A furnace was used to heat the columns that was designed for testing loaded columns in Tianjin, China. It consists of steel framework and four steel columns, with the furnace inside the framework. A hydraulic jack with capacity of 500 tons was used to produce load along the axis of the column, which is located on the bottom of the furnace chamber. The temperatures are measured with eight thermocouples, and the axial deformation is measured as the displacement of the jack which supports the column. The specimens have pinned-pinned conditions. The ambient temperature prior to testing was20oC, and the fire curve follows ISO-834. Temperatures were read at all of the thermocouples every minute, and axial shortening was measured at these intervals. According to ISO-834, a specimen is considered to have failed if contraction reaches .01L (mm), amd the rate of contraction has reached .003L (mm/min). All of the tests failed by overall buckling, and behaved in a ductile manner. The ‘limiting temperature’ refers to the temperature at which the member fails under fire and loading conditions; the limiting temperatures for these specimens ranged from 530-590oC. The study concludes that the larger the diameter, the longer time it takes to reach the same critical temperature. The effect of fire protection thickness is significant: a fire protection thickness of 15mm exhibits an increase in resistance time of 126 minutes, as compared to a specimen without fire protection.
Reference
Han, L.-H., Zhao, X.-L., Yang, Y.-F., and Feng, J.-B. (2003). “.Experimental Study and Calculation of Fire Resistance of Concrete-Filled Hollow Steel Columns” Journal of Structural Engineering, 129 (3), March, 346-356. doi: 10.1061(ASCE)0733-9445(2003)129:3(346)