Underground auditorium to seat thousand spectators

Abstract

The Arts and Crafts School of Paris was in need of an auditorium, with accommodation for one thousand persons, suitable for lessons and lectures. Owing to lack of space, it was decided to build it underground, below one of the courtyards. The choice of roof shape was an ellipsoid of revolution, whose major axis is inclined to the horizontal. The maximum diameter is 32 ms and maximum height is 10 ms. The thickness of the roof structure is 50 cms along the lower part, and 20 cms near the crown. This solution was of special interest as it overcame simultaneously two difficulties; namely, the foundation, when this has to be based on fill soil, and the non-interference with the illumination of nearby buildings. In this case the loading on the soil is always less than 380 grams per cm-, even assuming a local settlement of the soil over any area of 20 ms in diameter. Concrete has been transported to the required sites by means of compressed air chutes, with the result that the rate of concreting has not been interfered with. Formwork has been carefully thought out, especially over the zones where the floor surface changes into the auditorium vault. The tubular structure supporting the formwork of the vault has been erected with columns which are normal to the inclined diametral plane of the surface of revolution. Owing to this unusual arrangement, the staff working at the site have often lost their sense of balance.