Gallery construction particularly in large theatres, cinemas and public assembly halls, demands especial consideration in regard to structural design. No columns being permissible in the direct line of vision and fireproof construction being imperative,
ordinary constructional methods do not apply. In smaller structures of rectangular shape the gallery construction usually consists of raking beams supported at the rear end and towards the fore end by a conveniently placed main girder spanning the whole breadth of building. This method has limitations, however, becoming uneconomical as the breadth increases and inapplicable when the building is pear-shaped in plan or semi-circular at the rear end. In such cases cantilever construction of the type shown on Figure la may be employed with advantage.
W. Scott Wilson