How Precast Concrete Elements Are Lifted and Positioned

Introduction

Precast concrete construction moves large, heavy elements from a casting facility or storage yard into their permanent position in a structure. Between those two points, each element is lifted, transported and positioned by a team of crane operators, riggers and erection personnel working to an engineered plan.

Understanding that sequence — in full, in order — is the starting point for any engineering discussion about how workers interact with suspended precast elements, and where that interaction creates exposure. This article describes the sequence. Hazard analysis, engineering controls and the question of hands-free positioning are addressed in the articles that follow.

The Precast Element Family

The term precast element covers a wide range of structural and architectural concrete components cast off-site or on-site in a position other than their final location. [Source: Precast NZ Industry Guide 2015, §1.2]

Common types encountered in building and civil construction include:

• Wall panels — vertical elements used as external cladding or load-bearing walls. They may be solid, have window or door openings, or be sandwich-insulated panels. Typically tall and relatively thin in cross-section.
• Hollow-core floor slabs — prestressed floor units with longitudinal voids to reduce weight. Typically lifted without cast-in lifting inserts, using external clamps or slings. [Source: Precast NZ Industry Guide 2015, §10.3.2]
• Precast columns — vertical structural elements, typically square or rectangular in cross-section.
• Precast beams — horizontal structural elements in rectangular, L-shaped, inverted-T or other profiles designed to seat floor units on their ledges.
• Double-tees — wide floor or roof units with two downward-projecting stems, common in car parks and industrial buildings.
• Stair flights — full stair sections cast as a single unit, lifted and set onto landings.
• Tilt-up panels — wall panels cast horizontally on or near the building floor slab and tilted to vertical at the point of erection. [Source: OSHA SHIB 10-15-2003]

Each type has its own geometry, lifting insert arrangement and erection sequence. The sequence described in this article applies broadly across the family, with tilt-up panels noted separately where their sequence differs.

Lifting Inserts, Clutches and Rigging

Lifting inserts

Most precast elements are lifted using components cast into the concrete during manufacture — called lifting inserts. Inserts are designed by the precast engineer for the specific element, accounting for the element's weight, dimensions, sling angles, concrete strength at the time of lifting, and proximity of the insert to edges and openings. [Source: Precast NZ Industry Guide 2015, §4.1.1, §3.2.3] Reinforcing bars must not be used as lifting points. Before any lift, inserts must be inspected and confirmed undamaged, clear and compatible with the clutch to be attached. [Source: Precast NZ Industry Guide 2015, §10.3]

Lifting clutches

A lifting clutch engages the insert and connects it to the crane rigging. Clutches must be compatible with the specific insert type, visually inspected before each use, and rated for the loads to be applied. Clutches from different suppliers than the insert must be confirmed compatible before use. [Source: Precast NZ Industry Guide 2015, §4.1.2, §10.2]

Spreader bars and strongbacks

A spreader bar widens the sling geometry to reduce insert loads where sling angles would otherwise be too steep. A strongback is a beam bolted to the element face to add stiffness, distribute lift forces, or add supplementary lifting points. Where used, the strongback's weight must be included in the total lift weight calculation. [Source: Precast NZ Industry Guide 2015, §1.4, §3.2.4]

Taglines

Taglines — ropes attached to the suspended element — are used to control swing and rotation during crane travel and approach. Workers using taglines must remain a safe distance from the element. [Source: Precast NZ Industry Guide 2015, §1.4, §10.3]

The Erection Sequence

1. Preparation before the first lift

Before any element is lifted, the erection team confirms: crane capacity at the required reach; rigging and clutch compatibility; bearing pads, shims and anchor hardware in position; bracing components on hand; drop zone clear; and exclusion zones established. [Source: Precast NZ Industry Guide 2015, §10.2]

2. Pickup from storage or transport position

Wall panels and vertical elements are stored in A-frames or racks. Horizontal elements are stacked on dunnage at appropriate support points. Lifting clutches are engaged and the crane takes initial tension slowly — confirming all connections are seated and the element lifts level before clearing the rack. Individual elements must not be released from transport restraints until the crane has taken that element's load. [Source: Precast NZ Industry Guide 2015, §6.1, §6.2, §7.3.1]

For tilt-up panels, the panel begins horizontal. The crane lifts from face inserts and the panel rotates about its bottom edge, which remains on the casting bed until the panel is vertical. The bottom edge must not slide uncontrollably. [Source: Precast NZ Industry Guide 2015, §3.2.8]

3. Initial lift and stability check

Once clear of its support, the element is checked for correct hang attitude. If it tilts unexpectedly, the lift is lowered and the rigging reassessed before proceeding. Elements must be lifted in a controlled manner and restrained from uncontrolled horizontal movement. [Source: Precast NZ Industry Guide 2015, §10.3, §5.2.4]

4. Crane travel to the installation position

With the element stable, the crane moves it toward the installation position. Taglines maintain rotation and lateral drift control during travel. The crane operator must retain visual contact with the load wherever possible. [Source: Precast NZ Industry Guide 2015, §10.2]

5. Approach and final positioning

As the element approaches its installation position, crane movement slows and the erection crew moves from travel management into active positioning. The element must be brought onto its bearing surface — shims or bearing pads — while simultaneously aligning with adjacent elements, anchor bolt groups or other fixed references. At this stage, authorised erection personnel may need to be close to the element. The crane operator's visibility is often reduced as the element descends.

6. Landing and levelling

The element contacts its bearing surface and is levelled by shim adjustment. Shims must be on solid foundations, of appropriate material, and their total height is subject to design limits. [Source: Precast NZ Industry Guide 2015, §10.4] At this point the crane continues to support part or all of the element's weight until temporary bracing is in position.

7. Temporary bracing and stabilisation

Precast wall panels and tilt-up panels require temporary bracing to remain stable until permanent connections are made. [Source: OSHA 29 CFR 1926.704] Where possible, braces are attached before lifting. [Source: Precast NZ Industry Guide 2015, §10.3.3] Where not possible, the crane holds the element while braces are installed. [Source: Precast NZ Industry Guide 2015, §10.3.4] At least two braces are required for most panel configurations. [Source: Precast NZ Industry Guide 2015, §8.3.2]

8. Conditions required before crane release

The crane must not be released until: the element is at the correct position and confirmed level; all required bracing or propping is in place and connections made; the element is confirmed stable; and the erection supervisor has authorised release. [Source: Precast NZ Industry Guide 2015, §10.3, §8.1; OSHA 29 CFR 1926.704]

Where Erection Personnel May Need to Be Close to the Element

Several stages above require authorised erection personnel to work in close proximity to the suspended or recently landed element:

• During final positioning — to observe and confirm alignment with the seating, anchor bolts or adjacent panels
• During brace attachment — to connect brace hardware to panel face inserts and floor slab anchors while the crane holds the element
• During shim adjustment — to place or adjust levelling shims at or near the element base

These tasks require skill, judgement and planned working positions established before the lift begins. A rigid push-pull tool such as RiggerSafe® may be one option for specific, controlled, low-speed positioning tasks where the erection plan permits an authorised worker to approach and where a suitable working position exists — but it does not replace rigging design, taglines, exclusion zones, temporary bracing, crane control or the engineered erection procedure. Its application in precast wall panel erection is assessed in Hands-Free Positioning of Precast Wall Panels.