Skip to main content

How tower cranes work ?

These big birds of sky-high construction are engineering marvels 

Tower cranes fl ock to money. During the economic boom years, high-rise construction cranes migrated from Beijing to Shanghai to Dubai, where it was estimated in 2006 that there was one tower crane for every 44 residents of the desert boom-opolis. Tower cranes are feats of structural engineering that often outshine their creations. They are designed to stand 80 metres tall and reach 80 metres out supported only by a narrow steel-frame mast, a concrete foundation and several counterweights. The engineering principle that keeps the twiggy tower crane from tipping over is something called a ‘moment’. If you hang a weight from the crane’s jib arm, it exerts a 
rotational force or torque where the arm connects to the top of the mast. The magnitude and direction of this force (clockwise or anticlockwise) is called the moment. If the weight is hung close to the mast, the magnitude of the moment is lower than if the weight is hung far out on the jib. To keep the crane upright, counterweights are used to create a moment of equal magnitude in the opposite direction, balancing out the rotational forces. Once a tower crane meets its maximum unsupported height, it can be tethered to the building itself and continue to grow with the rising skyscraper. The tower cranes that rose with the construction of the record-breaking Burj Khalifa skyscraper in Dubai reached a truly dizzying height of 750 metres.

Self-assembling crane

 One of the most remarkable engineering feats of tower cranes is that they can literally build themselves. With help from a large mobile crane, construction workers secure the base sections of the tower and assemble the top unit of the crane – the slewing unit, jib and machinery arm. But before the top section of the crane is attached, workers slide a hydraulic climbing unit around the base of the tower. Once everything is in place, the hydraulic climbing unit lifts the entire top section of the crane (including the horizontal jib and operator’s cab) just enough to slide in a new section of tower beneath. Once the new section is secured, the hydraulic unit continues to climb up, section by section, as the crane slowly builds itself higher. 

Comments

Popular posts from this blog

How Energy conversion from coal is done?

Single generator sets of over 600 MW are now used in the UK, though there are many smaller generators in use. A 600 MW generator can supplythe average needs of over 1 million UK households. Three or four such generators are typically installed in a single large coal-fired station which isoften sited close to a coal mine, away from the city dwellers who consume the electricity. Such generators are usually driven by a compound arrangement of highpressure, intermediate-pressure and low-pressure turbines, increasing in size as the pressure decreases. Modern turbines rotate in a speed range from 1500 to 3500 r.p.m., usually 3000 r.p.m. for the UK’s 50 Hz system. For large coal-fired plant the steam pressure could be 25 megapascals (MPa) with steam temperatures of 500–600 °C to improve the thermodynamic efficiency. In nuclear reactors, which operate under less demanding conditions, the steam is superheated to about 5 MPa and 300 °C. Modern water tube boilers are complex and have ...

How ASPs works?

The Web and the Internet began to really heat up and receive significant media exposure starting around 1994. Initially, the Web started as a great way for academics and researchers to distribute information; but as millions of consumers flocked to the Internet, it began to spawn completely new business models. Three good examples of innovative models include:   • Amazon - Amazon (which opened its doors in July, 1995) houses a database of millions of products that anyone can browse at any time. It would have been impossible to compile a list this large in any medium other than the Web.   • Ebay - Online auctions make it easy and inexpensive for millions of people to buy and sell any imaginable item. It would be impossible to do this at a reasonable cost or in a timely manner with any medium other than the Web.   • Epinions - Thousands of people contribute to a shared library of product reviews. One of the Web's greatest strengths is its worldwide view a...

All about Electronics & Instrumentation Engineering)(EI)

  Vision : To be globally recognized as a seat of learning and innovation in Electronics for application to Communication, Transportation, Defence, Industry, Health Care, Entertainment, and many other consumer products.  Mission : 1). To produce quality engineers in the field of Electronics and related domains.  2) To conduct research and develop products in the fields of Chip design, Communication Systems, Electronics Instrumentation, Signal Processing and other related areas with strong emphasis on critical state of the art applications.  3) To grow in the area of Design and Manufacturing of chips, boards and systems.     Program Educational Objectives :  I.  To provide students a successful career in industry that meets the needs of national and multinational companies.  II.  To develop the ability among students to synthesize data and technical concepts for application to electronic product design and to solve real...