The hydraulic lifting method behind some of the most technically complex heavy lifts in construction
Definition
Strand jacking is a hydraulic lifting technique that uses bundles of high-strength steel strands and multi-strand hydraulic jacks to lift, lower or incrementally position heavy loads with precision. The strand passes through the jack in a cyclic grip-and-release sequence — upward strokes grip and lift; the strand feeds through on the return stroke. This gives strand jacking its defining characteristic: it can lift loads beyond practical crane capacity, reach or access — at heights and clearances cranes cannot reach.
A single multi-strand jack typically develops capacity from tens of tonnes up to 1,000 tonnes or more, depending on manufacturer and strand configuration. Multiple jacks are used in parallel for larger loads — synchronised hydraulically so that the lift remains level and load is distributed as designed. Capacities of several thousand tonnes are achievable with appropriately configured systems.
The lifting medium consists of multiple individual high-strength steel strands, typically 15.7–18 mm diameter in 7-wire construction, bundled to suit the required jack capacity. As an indicative example, a jack carrying around 90 such strands reaches a nominal capacity on the order of several hundred tonnes, approaching 900 tonnes depending on strand size and safety factor. The strand feeds through the jack body and engages wedge-type anchor grips on each stroke.
How a Strand Jack Lift Works
The sequence is cyclic. On the lift stroke, hydraulic pressure extends the jack ram, and wedge grips engage the strand — the load rises. At full extension, the upper anchors lock, the ram retracts, and the lower anchors release. The strand feeds through. The next stroke begins. Each stroke length depends on the jack model — refer to manufacturer specification for the applicable range. Over a full lift, thousands of strokes accumulate to reach the required height.
Control systems monitor strand load at each jack and adjust hydraulic pressure to maintain synchronisation. On multi-point lifts — lifting a bridge deck from four corners, for example — the control system ensures that no single jack carries disproportionate load as the structure moves.
Strand jacks can lower as well as lift, giving them a controlled descent capability that cranes at maximum radius cannot always provide.
Where Strand Jacking is Used
The method is applied wherever crane access is impractical, load capacities exceed crane limits, or precision control at height is required. On the London Eye, strand jacks rotated the fully assembled 120-metre diameter wheel from horizontal to vertical — a lift in which balance and controlled rotation were the governing requirements, not raw capacity.
On stadium roof erections, strand jacks lift pre-assembled roof structures from ground level to final bearing elevation. On bridge projects, strand jacking is used to thread new cables into cable-stayed structures, to lift precast segments into final position, and to provide controlled lowering of falsework after deck closure.
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Strand jack lift cycle — stroke sequence, grip engagement and multi-point synchronisation
Original diagram — EE&HL Network 2026 · In preparation
Frequently Asked Questions
Strand jacking is a hydraulic lifting technique that uses bundles of high-strength steel strands and multi-strand hydraulic jacks to lift, lower or incrementally position heavy loads with precision.
The strand passes through the jack in a cyclic grip-and-release sequence. On each upward stroke, wedge grips engage and the load rises. The ram retracts, the strand feeds through, and the next stroke begins. Stroke length depends on the jack model — refer to manufacturer specification for the applicable range.
Strand jacking is used where crane access is impractical, load capacities exceed crane limits, or precision control at height is required — including stadium roof lifts, bridge segment placement, cable installation and offshore operations.
