Sizes and Materials
Sizes of gang forms vary substantially from smaller units that are handled manually, to much larger units that are handled and raised by cranes. Smaller gang forms are typically 2 x 8 ft (0.61 x 2.44 m) and 4 x 8 ft (1.22 x 2.44 m), and weigh between 50 and 100 lb (23 and 45 kg). Larger gang forms are limited by crane carrying capacity and can reach 30 x 50 ft (9.1 x 15.2 m). Some literature refers to smaller gang units as ‘‘modular forms,’’ and to the larger units as ‘‘gang forms.’’
Gang forms can be made of aluminum (all-aluminum), plywood face and aluminum frame, plywood face and steel frame, and steel. All-aluminum gang forms consist of aluminum sheathing supported by an aluminum frame along with intermediate stiffeners. The aluminum sheathing can be plain or take the shape of a brick pattern for architectural finish. Aluminum sheathing is not popular because of its relatively higher cost and the tendency of concrete to react chemically with aluminum. A common module for all-aluminum gang is 3 x 8 ft (0.91 x 2.44 m) panels.
A more popular and widely used alternative to the all-aluminum gang forms is the aluminum frame with plywood. This system is lighter and less expensive than the all-aluminum gang form. Plywood is attached to the aluminum frame by aluminum rivets.
Another method of attaching plywood to aluminum beams is to use the nailer-type joists in the assembly of the gang form. The plywood is nailed to the nailer type beam by regular nails. A common module for this system is 2 x 8 ft (0.61 x 2.44 m) panels. Figure 6.4 shows a gang form with aluminum frame and plywood face.
The third type of gang forms consists of a plywood face supported by steel walers. Walers are typically made from double channels to allow ties to be inserted between the channels and to reduce the deflection of the gang form. The advantage of this sys
tem over the above mentioned systems is its ability to carry greater loads at longer distances between walers. A common module for this system is the 4 X 8 ft (1.22 X 2.44 m) panel.
The all-steel gang form is made of steel sheathing and steel studs and wales. This system is used to support fresh concrete for high, thick, and multiple lifts. This system has an unlimited number of reuses as long as good storage practices are followed. A common module for this system is the 2 X 8 ft (0.61 X 2.44 m) panel because of its heavy weight.