A 66-foot-diameter concrete sphere, flanked by a curving wall 26 feet high and 262 feet long, is the architectural focal point for a new technical-vocational school in Montpellier, France. The concrete shell will house the school's planetarium. The segmental wall and adjoining sphere at the Jean Monnet school were built in 4 months, using a standardized proprietary forming system adapted for the project. The entire formwork operation was done by a crew of five with one experienced supervisor.
During construction of the foundation slab the outer formwork of the sphere was preassembled in 10 prefabricated segments. After prefabrication on the ground they were lifted by crane and attached to previously erected segments. When the outer form for the lower half of the sphere was completed, reinforcing steel was put in place, supported off the form at the proper distance. Then the inner face of the form could be put in place. After the first row of form boards was inserted and wedged into place between the I-beams, concrete placement began. Form boards were set just ahead of the concreting, so that the placement proceeded in a helical path. The operation proceeded in much the same way for the upper half of the sphere, except the crew worked from the outside of the sphere instead of from the inside.