Rankine approach for fire resistance of axially-and-flexurally restrained steel columns

Traditionally, the Rankine equation has been applied to investigate the load bearing capacities of steel columns or frames at room temperature. Recently, the method has been extended to predict the fire resistance of a simply supported steel column by taking the temperature effects on steel material into consideration. This paper further extends the Rankine equation to predict the fire resistance of an isolated steel column from the surrounding structure. The complicated boundary restraints contributed by the adjoining structure are represented by a linear spring and a pair of rotational springs attached to the column ends. Both the boundary restraints and creep strain are incorporated into the Rankine equation. The predictions of Rankine approach are verified experimentally and numerically. Generally, it is shown that under different external load utilization factors and boundary restraint levels, Rankine approach yields accurate and slightly conservative predictions.