A system developed in Austria for forming axially symmetrical curved structures such as funnels, cones, shafts, sewage digestion tanks, and water towers permits continuous placement of concrete without form ties. It is thus suitable for water-retaining structures, and they frequently can be built without cold joints, eliminating the use of waterstops. Bracing and work platforms are an integral part of the form system, and additional shoring to the ground is ordinarily not required.
FORMING CONE AND FUNNEL SHAPES
Formwork for conical and egg-shaped tanks and water towers is made of radial steel I-beam supports with small trapezoidal panels about 20 inches high wedged tightly between them.
Steel formwork for cylindrical structures up to 130 feet in diameter is fabricated with rigid tubular steel rings that hold inner and outer sheathing.