Steel has a thermal expansion coefficient of 7.3E-6 in/in/deg-F. So if you assume that fire is uniformally heating a 53 foot long beam at delta-temperature of 2500 degrees F, that means the beam will want to expand axially about 11.6 inches or roughly one whole foot. If the beam is constrained and cannot expand, it will bend inducing compressive and tensile stresses in the beam while exerting forces at the connections. The beam can either fail due to buckling, or due to the failure of connection joints. If too many critical members fail, the building will eventually collapse after a domino-like effect.
Now I don't claim to be an expert, but I do have a B.S. in Mechanical Engineering if that lends me any credibility. In my opinion, it is possible for fire to cause a (poorly designed) steel building to collapse.
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