science

Strand jack

Strand jack is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Strand jack rather than just read about it. In short: A strand jack (also known as strandjack) is a jack used to lift very heavy loads (e.g. thousands of tons or more with multiple jacks) for construction and engineering purposes. Strandjacking was invented by VSL Australia's Patrick Kilkeary & Bruce Ramsay in 1969 for concrete post tensioning systems, and is now widely used for heavy lifting, to erect bridges, offshore structures, refineries, power stations, major bui…

Key takeaways

Strand jack belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Strand jack to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Strand jack from memory before moving on to harder problems.

Reference excerpt

A strand jack (also known as strandjack) is a jack used to lift very heavy loads (e.g. thousands of tons or more with multiple jacks) for construction and engineering purposes. Strandjacking was invented by VSL Australia's Patrick Kilkeary & Bruce Ramsay in 1969 for concrete post tensioning systems, and is now widely used for heavy lifting, to erect bridges, offshore structures, refineries, power stations, major buildings and other structures where the use of conventional cranes is either impractical or too expensive.

Use

Strand jacks can be used horizontally for pulling objects and structures, and are widely used in the oil and gas industry for skidded loadouts. Oil rigs of 38,000 t have been moved in this way from the place of construction on to a barge. Since multiple jacks can be operated simultaneously by hydraulic controllers, they can be used in tandem to lift very large loads of thousands of tons. Tandem use of even two cranes is a very difficult operation.

How it works A strand jack is a hollow hydraulic cylinder with a set of steel cables (the "strands") passing through the open centre, each one passing through two clamps - one mounted to either end of the cylinder. The jack operates in the manner of a caterpillar's walk: climbing (or descending) along the strands by releasing the clamp at one end, expanding the cylinder, clamping there, releasing the trailing end, contracting, and clamping the trailing end before starting over again. The real significance of this device lies in the facility for precision control. The expansion and contraction can be done at any speed, and paused at any location. Although a lone jack may lift only 1700 tons or so, there exist computer control systems that can operate 120 jacks simultaneously, offering fingertip feel movement control over extremely massive objects.

In construction Strand jacking is a construction process whereby large pre-fabricated building sections are carefully lifted and precisely placed. The alternative would be to do all assembly in situ, even if expensive, technically risky, or dangerous. Strand jacks used for heavy lifting and skidding operations are owned and operated by a large number of construction and heavy lifting companies around the world. They are manufactured by a small number of companies based in Europe.

Notable uses Kursk submarine disaster Erection of the London Eye wheel. Uses outside of construction

Costa Concordia disaster, in the ship salvage phase.

References

Illustrations

Worked examples

Example 1 — a first encounter with Strand jack

Start with the simplest possible case. Write down what Strand jack claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Strand jack before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Strand jack ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Strand jack

In research: Strand jack appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Strand jack in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Strand jack is common in secondary-school and first-year university syllabi. It links to neighbouring topics Construction equipment, Machines, so understanding it makes those chapters shorter.
In everyday life: Look for Strand jack outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Strand jack in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Strand jack means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Strand jack out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Strand jack in simple terms?

Why does Strand jack matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Strand jack?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Strand jack.