Steel, although a non-combustible material, has a very low fire resistance value. With an increase in temperature, it becomes softer and, therefore, decreases in resistance to the effects of tension and compression. At about 600 °C, its yield stress drops to only one-third of its value at normal temperature. When the steel members come in contact with the water used to extinguish the fire, they shrink, bend or distort, thereby jeopardizing the stability of the entire structure. In practice, it has been observed that unprotected steel beams buckle and steel columns buckle, resulting in collapse of the structure. Therefore, the fire-resistant properties of a structure require that all structural steel members be protected by covering with some insulating material. This can be achieved by completely covering the steel members with materials such as bricks, burnt clay blocks, terra cotta or concrete.
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