restrained and unrestrained assemblies in fire rating

huangyhg

restrained and unrestrained assemblies in fire rating
hi guys,
need to know what does it meant by restrained and unrestrained assemblies as per ulc fire rating. for unrestrained it gives less fire rating time compared to restrained. but what is actual restrained and unrestrained conditions for beams and other components.

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restrained condition is where the end connections offer considerable restraint for arching action to occur under the action of fire. if the ends are unrestrained, no thrust can be developed and hence, no arching action. the cover requirements are higher for unrestrained conditions.
thanks.