Dill1 concludes that, while exposure to fire will almost certainly cause warping and twisting of members, it does not inevitably follow that the strength of the steel is reduced. It is almost certain that any steel that has been heated hot enough to undergo damaging grain coarsening or that has been cooled rapidly enough to harden it will be so badly distorted that it would have no consideration for re-use anyway. This leads to the general statement that steel that has been through a fire but that can be made dimensionally re-usable by straightening with the methods that are available may be continued in use with full expectation of performance in accordance with its specified mechanical properties. Essentially then, the question is one of economics: if the steel can be straightened for less money than fabricating and installing a new piece, then that should be done.
Two possible exceptions to the above include quenched and tempered structural steels and high-strength fasteners. The mechanical properties of such heat-treated items may be affected by prolonged fire exposure and should be tested to determine the effects of the fire, if any.
Another reference is Council on Tall Buildings and Urban Habitat2. See also 11.2.4.
 Dill, F.H., 1960, "The Effects of Fire on Structural Steel," Proceedings of the 1960 AISC National Engineering Conference, AISC, Chicago, IL.
 Council on Tall Buildings and Urban Habitat, 1980, Monograph on Planning and Design of Tall Buildings, Volume CL, Tall Building Criteria and Loading, ASCE, Reston, VA.
 R. H. R. Tide, “Integrity of Structural Steel After Exposure to Fire”, Engineering Journal, First Quarter, 1998, pp. 26-38.
last modified 1 January 2006