In the modern construction industry, prefabricated building technology is transforming traditional construction methods with its advantages of high efficiency, environmental friendliness, and controlled quality. During the production, transportation, and installation of prefabricated components, the importance of lifting and anchoring systems, as key components connecting components to lifting equipment, is self-evident. More than just simple connectors, they provide a safety guarantee for the entire component, bearing its weight.

Definition and Function of a Lifting Anchor

A lifting anchor is a mechanical anchor pre-embedded within a concrete structure, designed specifically for lifting. It works with a lifting device (clutch, eye, shackle, etc.) to form a removable temporary lifting point. Its main functions include:

Safely transmitting lifting force to the concrete structure;

Preventing local damage such as splitting and edge chipping during lifting;

Enabling rapid hooking and unhooking, improving the operating efficiency of tower cranes or mobile cranes;

Meeting the complex load requirements of multiple turnovers (demolding, flipping, and on-site repositioning).

A typical lifting anchor system typically consists of three components:

Anchor rod: The portion embedded in the concrete, typically with a hook, thread, or a special tail shape (such as a wavy shape) to ensure maximum grip with the concrete and prevent pullout.

Exposed portion: The structure used to connect the lifting device, which can be a eye, threaded hole, or ball head.

Lifting device: The component used with the lifting anchor, such as a shackle or specialized sling, connected between the crane hook and the anchor.

The following are common lifting anchor types and characteristics used in precast components.

1. Spherical Head Anchor

Construction: Round steel with a forged spherical head on one end and an anchor foot or straight rod on the other; used with a lifting clutch.

Advantages:

360° rotation and oscillation to accommodate diagonal tension;

Small anchor head embedment depth, suitable for thin-walled panels;

Automatic clutch lock, installation and removal takes seconds.

Load range: 1.3–32 t.

Applications: General components such as staircases, exterior wall panels, columns, and beams, especially suitable for diagonal tension or tilting applications.

2. Threaded Socket/Foot Anchor

Construction: Thick-walled socket with a bottom anchor foot (or corrugated tail), internally threaded for eyebolt connection.

Advantages:

The lifting point is flush with the concrete surface, resulting in a clean appearance;

Replaceable bolts can be reused repeatedly;

Balanced shear and tensile properties. Load range: 0.5–20 t.

Applications: Components requiring high aesthetics, such as exposed concrete exterior walls, decorative panels, and pipe gallery roofs.

3. Double Head Anchor

Construction: A single anchor rod with forged ends and equipped with a dual-point clutch.

Advantages: Two-point load application, minimal out-of-plane deflection, and smoother rollover.

Applications: Rollover of slender components such as large floor slabs and hollow bridge decks.

4. Spread Anchor

Construction: The lower end of the anchor rod spreads out in a "swallowtail" or "fishtail" shape.

Advantages: Load distribution, reducing the risk of splitting at thin-wall edges.

Applications: Stair treads, balcony railings, and precast decorative tiles with a thickness of less than 80 mm.

5. Wavy Tail Anchor

Construction: The anchor tail is bent into a "wavy" shape in multiple sections, increasing the anchoring length. Advantages: Provides high pull-out strength without requiring additional anchors; suitable for low-strength early-stage concrete.

Applications: Components requiring rapid demolding, such as pipe corridors, box culverts, and thin-walled beams.

6. Disk Anchor (QuikLift® Disk)

Construction: Short rod + large-diameter disk. Used for the outer panels of sandwich insulated walls.

Advantages: Single-point lifting without penetrating the insulation layer; the disk provides a large bearing surface.

Applications: Lifting the outer panels of prefabricated sandwich insulated walls to avoid cold bridging.

7. Pin Anchor

Construction: Plain round pin + removable adapter head with a tapered hole.

Advantages: Low cost; the adapter head is recyclable; after removal, only a small tapered hole remains, making it easy to repair.

Applications: Components with low to medium loads, such as pipelines, box culverts, and curbs.

The selection and use of lifting anchors is not arbitrary and requires consideration:

Working load: The weight of the component to be lifted.

Dynamic factor: The effects of dynamic loads caused by sudden starts and stops during lifting. This factor is typically multiplied by a safety factor (e.g., 1.5 or higher) based on the static load.

Concrete strength: Concrete strength is typically low during demolding, and it is essential to ensure that it is strong enough to withstand the lifting forces.

Lifting angle: The angle between the slings significantly increases the actual load on the anchor rod; 60 degrees is a common and recommended angle.

Safety factor: The lifting anchor is designed with a high safety factor (typically ≥3 for the material itself and ≥2.5 for concrete cone failure) to ensure a safe and reliable lift.

Component shape and center of gravity: The number and location of anchor points must be calculated to ensure a balanced lift.