What are Form Ties in Construction?
What are Form Ties in Construction?
Form ties are mechanical devices that connect opposite faces of wall formwork to restrain the applied concrete pressures. They transmit loads in tension between stiff vertical and/or horizontal members associated with the main formwork.
Form ties are used to connect opposite faces of wall formwork to restrain the applied concrete pressures. They transmit loads in tension between stiff vertical and/or horizontal members associated with the main formwork. The concrete is held in place by these form ties when it is poured into place, allowing it to set quickly.
Form ties are usually made out of steel or aluminum, depending on what is available locally. Steel form ties are more commonly used because steel is stronger than aluminum and can withstand higher compressive forces without deforming or breaking.
Form tie installation requires expertise from a professional contractor who knows how to navigate around obstacles such as electrical boxes, plumbing pipes and heating ducts without damaging them during installation.
Types of Form Ties
Form ties are used to hold forms in place while concrete is poured and set. There are two main types of form ties: continuous single member ties and internal disconnecting ties.
Continuous single member ties are one-piece units that require special holding devices to secure them in place. They cannot be removed from hardened concrete and must be broken to be removed.
Examples of continuous single member ties include flat ties, loop ties, fiberglass ties, and snap ties.
Internal disconnecting ties contain threaded ends that allow external members to be removed without breaking or pulling. These ties are classified into two types: she-bolt ties and bulb ties.
She-bolt ties consist of an inner tie rod with threaded ends and two outer she-bolt members, while bulb ties contain an inner tie rod with a bulb at one end and an outer tie rod with a threaded end.
Both types of internal disconnecting ties can be removed from hardened concrete and can be reused. The selection of the appropriate form tie system depends on the type and size of the formwork, the strength and stiffness required, and the intended reuse of the ties.
