Fire protection

Since steel was first used as a structural framing material, most regulatory standards have required that it be protected from high-temperature fire. Two options have been commonly used; either thermal insulation to separate the steel from fire or water sprinklers to put the fire out or cool the steel. For nearly a century the standards for fire protection have been based either on tradition or tests in specialized furnaces, practices that often resulted in immoderate protection requirements. As more and more of the world's population moves to ever-expanding urban areas, developers are exploring new avenues for protecting structures and their occupants, finding new ways to make the fire protection of steel more effective and economical.

The first of these is the transition from very expensive real-life testing to quicker and less expensive calculations using sophisticated computer models. Gradually, as calculation methods are being refined and regulatory authorities become confident in applying them, savings in steel protection can be realized in many ways. More realistic evaluation of fire conditions results in more precise application of protection, allowing for the elimination of excessive protection.

For structures such as those that use an exposed frame as an architectural feature, thermal insulation can be replaced with liquid filling of tubular members. If the members are hydraulically connected and the heated liquid is free to move, the steel frame is able to dissipate its thermal load through convective transfer to other, non-heated segments of the frame.

In another development, a Japanese steel producer has adapted technology developed for steels used in elevated temperature applications to the steels used for building frames: constructional steels have been developed which have superior residual strength characteristics at temperatures above 500 C. While not eliminating the need for fire protection, the special steels for this application require less protection than steels traditionally used.

The total cost of a completed structural frame includes the cost of the steel components, of fabrication, shipping and erection, plus the cost of fire protection. Studies in the United Kingdom have shown that for those cases where fire protection is a significant part of the total cost, it is possible to economically replace protection with additional steel. The concept is that a heavier, structurally overdesigned frame can tolerate higher temperatures. In addition, because of their larger size, heavier frame members heat up less quickly in a fire. The end result is the calculation of cost trade-offs in which more steel may be the route to more economical protection.