23-09-2008, 12:27 AM
It is often desirable for structural steel members to pass through a fire wall
or common wall rather than being curtailed on each side of the wall. In such cases, the penetrating member will often be fire protected for a certain length on each side of the wall so as to minimise the possibility of fire spread through heat conduction and excessive temperature rise of the member on the unexposed side of the wall. This latter aspect is necessary to ensure that lateral restraint will continue to be provided to the top of the wall by the member on the unexposed side of the wall.
Such fire protection can be costly and it is not clear that it is necessary. The reasons for this is that although a steel member is heated intensely on one side of a wall, this heat will be readily conducted to the unexposed side where it will be lost by radiation and convection to the surroundings. Some heat will also be conducted into the concrete wall.
The ability of a penetrating member to act as an effective bracing member depends on the temperature of the member on the unexposed side of the wall: if the member is too hot, it will have insufficient stiffness to provide effective restraint. Similarly, high temperatures could lead to ignition of combustibles should these be in contact with the members on the unexposed side. .. .