Inexpensive reusable inflated forms are the basis of a patented system for building small bridges and culverts easily and rapidly. The three-step method involves:
- Inflating a closed-end cylindrical fabric form, and shaping it with metal tie-down straps
- Placing reinforcing steel on bar supports over the inflated form.
- Shotcreting several inches of concrete over the top in a single layer.
- The forms can be used as many as 40 to 50 times, and one form can be adjusted to build many sizes of culvert arch or other structures such as large diameter concrete pipe, tunnel linings, water tanks and buildings--either earth-sheltered or above ground. No shoring is needed and the form requires no cleaning or surface preparation.
A key feature is adjustability. By restraining the inflated fabric at intervals with inexpensive steel strapping, various shell sizes down to 2 feet in diameter can be created with the same form. This versatility reduces the contractor's initial form cost because he can use one form or one set of forms to make many shapes. One of the most promising uses for the cylindrical air-supported forming system is for drainage structures.