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When fire occurs in a building, the structural parts tend to expand under the effects of the resulting heating. Thermal expansion of structural building components may be variously restricted according to the resistance offered at the supports or by the stiffness of abutting constructions. Restriction of thermal expansion has been shown by many fire tests and by evidence from building fires to have an important influence on the structural behavior of building elements during exposure to fire. Described in this paper are results and impressions gained in an exploratory study of the effect of varying intensities of restraint of the thermal expansion of precast, prestressed concrete double-tee floor elements during the course of standard fire exposures. The principal variable in the study was the amount of linear expansion along the axis of the span allowed before further expansion was stopped. Relationships between given expansions, the resulting expansion forces, and midspan deflection are presented. The changes in the location of the center of thrust at the ends of the members during the course of the fire exposure are discussed. Further investigations on the subject of restraint are suggested.

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