Types of Form Ties Used in Formwork

Form ties are essential accessories for formwork and provide many benefits. They are used to hold the formwork in place and help to maintain the desired dimensions and shape of the structure as the concrete is being poured and cured. Form ties are available in a variety of types, shapes, sizes, and materials, making them ideal for projects that require frequent formwork adjustments.

What is a Form Tie?

Form ties are essential accessories for formwork and provide many benefits. They are used to hold the formwork in place and help to maintain the desired dimensions and shape of the structure as the concrete is being poured and cured. Form ties provide increased strength and stability to the formwork, allowing it to withstand the pressure of the concrete being poured. They are easy to install and remove, making them ideal for projects that require frequent formwork adjustments. Additionally, form ties are cost effective, as they can be reused multiple times. They are also available in a variety of shapes, sizes, and materials, allowing them to be used in different applications.

Types of Form Ties

1. Continuous Single Member type:
   • This form tie consists of a single steel member that runs continuously around the formwork. This type of form tie can be used in circular and rectangular forms. It is used to hold the formwork in place and to provide a uniform pressure to the formwork. This type of form tie is usually used for smaller structures with minimal loads.
2. Internal Disconnecting type:
   • This form tie consists of two separate steel members that are connected to each other internally. This type of form tie is typically used for larger structures with heavier loads. It is used to hold the formwork in place and to provide a uniform pressure to the formwork. This type of form tie also provides flexibility to the formwork as it can be disconnected at any point.

Continuous Single Member type:

Continuous single member ties are often referred to as one-piece ties. They are held in place in concrete forms by special holding devices, and after the concrete has hardened some of these ties can be completely removed, while others must be broken to be taken out. The various types of continuous single member ties are listed below.

1. Flat Tie: Flat ties are one of the most common types of continuous single member ties. They are simple to use and provide a secure connection between two pieces of concrete.
2. Loop Tie: Loop ties are a more secure type of continuous single member tie. They are used when a stronger connection is needed between two pieces of concrete.
3. Fiberglass Tie: Fiberglass ties are often used when a lightweight and corrosion-resistant single member tie is required. They can be bent and twisted to fit most forms and are resistant to cracking and breaking.
4. Snap Tie: Snap ties are designed to be easily installed and removed. They are often used in applications where quick and easy installation is required.
5. Taper Tie: Taper ties are designed to provide a secure connection between two pieces of concrete while also allowing for slight movement. This makes them ideal for applications that require a tight connection but may also need to move slightly due to environmental conditions.
6. Threaded Tie: Threaded ties are a type of continuous single member tie that is designed to provide a secure connection between two pieces of concrete. They are threaded into place and can be easily adjusted if needed.

What is a Flat Tie?

A flat tie is a thin flat steel plate with holes at each end. These holes are used to lock the tie into forms using a wedge and pin. Flat ties are preferred for prefabricated modular form panels and light-duty applications.

Advantages of Using Flat Ties

Flat ties provide several advantages, such as being a one-time use product, meaning they cannot be removed from hardened concrete. Additionally, flat ties are easy to install and are relatively affordable. They also provide a secure connection that is less likely to move or rotate during the pouring process.

Removing Flat Ties

Flat ties are removed by braking and to facilitate braking, a notch is provided at a predetermined distance from its ends. To further ensure the tie does not rotate during braking, holes may be provided in its middle portion.

Uses of Flat Ties

Flat ties are commonly used in the construction industry to hold forms in place during the pouring of concrete. They can also be used for other structural applications, such as reinforcement or to attach a structure to another.

What is Loop Tie?

Loop tie is a single metal bar with looped ends, designed to provide space for locking systems such as wedge and pin. It is a preferred solution for prefabricated modular form panels and for light duty purposes.

How does Loop Tie Work?

Loop tie is designed to be permanently embedded in hardened concrete. It has a weaker cross section to prevent it from being easily removed from the concrete. Additionally, part of the middle of the loop tie is crimped to prevent it from turning against braking.

Advantages of Loop Tie

Loop tie offers a number of advantages for light duty purposes and prefabricated modular form panels. It is permanently embedded in concrete, meaning it can’t be removed or stolen. The loop tie also has a crimped middle portion which prevents it from turning against braking. This ensures that the loop tie remains securely in place. Additionally, loop tie is a cost-effective option compared to other locking systems.

Loop tie is a single metal bar with looped ends, designed to provide space for locking systems such as wedge and pin. This locking system is ideal for light duty purposes and prefabricated modular form panels. It is permanently embedded in hardened concrete and has a crimped middle portion to prevent it from turning against braking. Loop tie is also a cost-effective solution compared to other locking systems.

3. Fiberglass Tie

Introduction to Fiberglass Ties: Fiberglass ties are a new type of tie system created from glass fibers and resin materials. This system offers greater length and can be cut to size according to the requirements.

Installing Fiberglass Ties: Fiberglass ties are secured to form panels using a combination of grippers and tie wedges. After the concrete has hardened, the ties can be cut at the surface level, leaving no holes behind.

Benefits of Fiberglass Ties: Fiberglass ties offer enhanced flexibility as they come in a variety of colors, and they can also support greater loads compared to flat, loop, and snap ties.

What is a Snap Tie?

A snap tie is a metal rod that has enlarged buttons or loops on both ends for easy use with suitable tie holders. Plastic cones, metal washers, or pins are used to attach the tie for form spreading and water leakage prevention from concrete.

Why are Snap Ties Unique?

Snap ties are unique because they are permanent and cannot be removed from hardened concrete. This is due to the tie having a weaker cross section, which makes it easier to snap. In order to prevent the tie from turning inside the wall, a portion of the tie is crimped or weakened at a specific distance to make it easier to break.

How are Snap Ties Used?

Snap ties are used to form spreaders and prevent water leakage from concrete. The tie is attached to plastic cones, metal washers, or pins, and the breaking of the tie should only be done after the concrete has hardened. This will ensure that the tie snaps properly and does not turn inside the wall.

5. Taper Tie

What is a Taper Tie?

A taper tie is a rod that is threaded on both ends, designed to be inserted into formwork to secure them in place. It comes in standard lengths ranging from 34 inches to 60 inches, allowing for a variety of wall thicknesses to be achieved. The diameter of the rod tapers from a larger threaded end to a smaller one. After the concrete has hardened, the taper ties can be removed and reused.

How to Use a Taper Tie

To ensure easy removal, the taper tie should be greased before installation. Once the formwork is in place, the taper tie is inserted and locked by using wing nuts and washers. After the concrete has hardened, the taper ties can be removed and reused.

Benefits of Using a Taper Tie

The main benefit of using a taper tie is that it allows for easy removal once the concrete has hardened, making it a reusable product. It also allows for a variety of wall thicknesses to be achieved, making it a versatile product.

6. Threaded Tie

What is a Threaded Tie?

A threaded tie is a metal rod with a thread running along its entire length. It is secured to forms using nuts and washers at each end. It can be removed from hardened concrete if a plastic sleeve is fitted around it. The sleeve bonds with the concrete, allowing the threaded tie to be removed and reused. It can handle heavier loads when two nuts are used at each end.

Benefits of Threaded Ties

Threaded ties offer a number of advantages when used in concrete construction. They are easy to install, have a high load capacity, are reusable, and can be removed from hardened concrete with minimal effort. Additionally, they can be used for a variety of applications, including reinforcing walls, columns, and foundations.

How to Use Threaded Ties

Threaded ties can be installed quickly and easily. The metal rod is placed through the form, and the nuts and washers are secured at each end. If the tie is going to be removed from the concrete, a plastic sleeve is placed around the rod. This bonds with the concrete and allows for the easy removal of the threaded tie when the concrete has hardened. For added load support, two nuts can be used at each end.

Types of Internal Disconnecting Ties

Internal disconnecting ties are essential components used in construction to secure two or more members together. These ties are classified into two types: she-bolt ties and coil ties.

She-Bolt Tie: A she-bolt tie is a type of internal disconnecting tie which features threaded ends. This allows the external members to be removed without any breaking or pulling. They are used in a variety of structural connections, such as in roofs, walls, and columns.

Coil Tie: A coil tie is another type of internal disconnecting tie which is made of steel wire. It can be formed into a variety of shapes and sizes and is used to secure two or more members together. It is designed to provide secure and reliable connections which can be quickly and easily released.

1. The She-Bolt Tie System Explained

The she-bolt tie system is a secure and effective way of joining formwork during concrete pouring. It consists of an inner tie rod and two she-bolt members, each with one normal threaded end and one tapered end with a threaded hole. The tapered end is inserted into the formwork, with the tie rod being screwed into the threaded holes on both sides of the she-bolts. External threaded ends of the she-bolts are then secured to the formwork using a combination of wing nuts and washers. Once the concrete has hardened, the inner tie rod remains in the concrete, whilst the she-bolts can be removed and reused.

2. What is a Coil Tie?

A coil tie is a construction component used to ensure the integrity of concrete structures. It consists of two members: an inner tension member and an external holding member. The inner tension member is made up of two helical coils welded to the ends of two or four steel struts, which remain embedded in the concrete after it hardens. The external holding member consists of two bolts that are screwed into the coils at each end and supported by a washer and wale arrangement. These bolts can be removed and reused after the concrete hardens. Two strut coils are used for medium works, while four strut coils are used for heavier works. If needed, plastic or wood cones can be placed at each end of the coil to act as form spreaders. If the thickness of the wall is too large, two inner members connected by a threaded rod can be used.

Inner Tension Member:

The inner tension member of a coil tie consists of two helical coils welded to the ends of two or four steel struts. These components remain embedded in the concrete after it hardens, providing an inner layer of stability and strength to the structure.

External Holding Member:

The external holding member of a coil tie consists of two bolts that are screwed into the coils at each end, and supported by a washer and wale arrangement. These bolts can be removed and reused after the concrete has hardened.

Two vs Four Strut Coils:

Two strut coils are used for medium works, while four strut coils are used for heavier works. This is due to the increased strength and stability that the additional struts can provide, allowing the tie to better withstand greater loads.

Form Spreaders:

If necessary, plastic or wood cones can be placed at each end of the coil tie to act as form spreaders. This helps to evenly distribute the load placed on the tie, ensuring that the concrete forms correctly and the tie remains in place.

Threaded Rods:

If the wall thickness is too large, two inner members connected by a threaded rod can be used. This provides additional support and stability to the tie, allowing it to better withstand greater loads.

Load Capacity Range of Different Form Ties

Form ties used in construction come in a variety of sizes, types, and load-bearing capacities. The range of load capacity for different form ties can vary depending on the type, size, and material used. Generally, form ties can range in load capacity from 500 pounds to over 25,000 pounds. The most common form ties used in construction are steel and plastic, with each having a range of load bearing capacities. Steel form ties can have capacities ranging from 500 pounds to over 18,000 pounds, while plastic form ties can have capacities ranging from 500 to 25,000 pounds.