The BIG climb
04 March 2008
A number of different systems have been developed by manufacturers to raise tower cranes from one operating level to the next. While in the old days rope systems were used, sometimes even relying on the crane's hoisting winch, modern devices use one or more hydraulic rams. The main difference among them is in the means employed to overcome the limited height of a typical hydraulic cylinder's stroke.
Most systems are developed by the tower crane manufacturers and work with that tower. Especially in the US and Japan, however, specialized crane accessory manufacturers have developed their own systems suitable for cranes of different brands. The various types of internal climbing system include:
Stationary crane with rope operated jumping frame
In the late 1970s, large capacity tower cranes for heavy high rise steel erection work were only available as customer-made machines. American Bridge and Manitowoc developed a simple but effective way to convert Manitowoc 3900W2 and 4100W crawler cranes into self climbing tower cranes.
The upper cranes were installed on Favco towers, connected to the so-called jumping frame. The frame was supported by a column bracket and pinned members (flippers) that could be rotated for clearance during jumping. Beams with electric hoists were erected and connected to the tops of the columns in the bay where the crane was located.
Next, the crane, free standing about 30 meters (98 feet 5 inches) high on the jumping frame, was hoisted to a higher set of column brackets. Originally this hoisting process was done by steel riggers simultaneously operating hand winches at each column corner under the supervision of an engineer who had to keep an eye on the crane to make sure that it was kept in balance.
A similar jumping platform with integrated retractable support outriggers and electric winches based on top of the edge columns of the bay of the crane is still provided by Cornell for its TG luffing jib crane range. The main benefit of the system lies in the absence of any second upper support frame typical for European style internal climbing cranes. In addition, climbing steps can be easily adapted to the building requirements as well as the actual size of the jumping frame.
Floor climbing system with yoke and hydraulic ram
Typically for European construction crane design, like BKT, Manitowoc Potain and Linden for example, one or two hydraulic rams at the lower climbing collar lift the crane by a yoke (climbing traverse) that grips into lugs at the tower. Due to the limited extension of the hydraulic rams, several climbing steps are used to reach a new working level. Reinforced mast sections must always be located just opposite the climbing collars, setting limits to the freedom of the climbing distances from one working level to another. While the crane is on two climbing collars, a third set has to be installed ahead of further jumping the crane. In addition, the whole hydraulic jacking system has to be reinstalled on the second climbing collar.
This system is widely used by European manufacturers, for example, BPR-Richier, Liebherr and Wolff. In contrast to the floor climbing system with yoke and hydraulic ram method, the hydraulic jacking system remains located in the base section of the crane tower. A pair of steel ladders is hung on opposite sides of the crane tower, supported from the upper climbing collar. Dogs in the special base tower section engage on rungs, or slots, of these ladder devices, moving up the ladders and engaging new slots as the central lifting cylinder is actuated.
Before jumping the crane from one working level to the next, the climbing ladders have to be relocated and a new climbing collar has to be installed. Driven by recent high rise concrete building projects, Liebherr has developed a new 200IC internal climbing tower with outer dimensions of just 1.6 by 1.6 meters (5 foot 2 inches by 5 foot 2 inches) and a 256/355IC tower with 1.9 by 1.9 meters (6 foot 2 inches by 6 foot 2 inches) square size. The outer dimensions of these towers are smaller than the standard Liebherr HC tower system to cope with small lift shafts.
Long stroke rams
Cornell in the US and, originally, Favelle Favco, use a hydraulic extension of rams sufficient to raise the crane one entire typical floor height. If over-height floors must be climbed, intermediate steps must be arranged. At the tower base there are three telescopic beams. The middle one is connected with the hydraulic rams to raise the whole crane before the two outer ones are extended at the next level to support the crane.
Lifting column climbing system
This jacking device is realized on Kodiak cranes and can also be used for climbing inside an outer tower system as for floor climbing. A long column rests atop a beam that supports the crane at the old climbing level. Inside the crane tower hydraulic cylinders with a lifting saddle move alongside that column furnished with holes where, for every climbing step, a pin is inserted. Despite the fact that the climb is limited to the column's length, the fast working Kodiak jacking system enables a four-floor climb.
Japanese-style floor climbers
In contrast with most European climbing cranes, on Japanese tower cranes new tower sections are inserted through the slewing ring. The upper crane, therefore, can also climb alongside the crane tower, providing a real benefit for layout as an internal climbing crane. In operation mode, Japanese cranes are connected to the crane tower with an upper and lower lifting frame by pins hydraulically inserted into holes on the tower. By withdrawing the upper pins, and extending two main cylinders working alongside the tower, the upper frame elevates itself. Then the upper frame is locked again by pin and the lower frame is unlocked. By compressing the main cylinders the lower frame elevates itself.
As the tower elevates in small steps the connected foundation frame with retractable or foldable outriggers is lifted from the ground to the next suitable floor level. During that period the crane tower passes through the turntable and, usually, a hole in the boom foot section, while the machinery deck is resting with support beams connected to the upper climbing frame on the already built floor. As soon as the tower crane foundation frame rests on the designated floor level, the complete upper crane climbs the tower to its full free standing height.
The crane can climb alongside the whole, usually 30 to 45 meter (98 to 108 foot) tower, so this system is not tied to strictly rising by the height difference of a floor level. In addition, the climbing system is identical to the external climbing procedure, where tower sections are added through the turntable and the crane just climbs up again alongside the tower to the very top.
No investment is needed in extra equipment to transform the crane into an internal climbing type. In general, the tower crane base can be easily adapted to the actual building bay using additional support beams with extendable shoes and even can be designed in a special way to accommodate the crane tower outside the centre of the bay.
The specialized tower crane base, working as a sole support of the elevated crane, is not always designed by the manufacturer of the crane upper. Yoshinaga Manufacturing Co. Ltd is the market leading company in highly sophisticated upper support beam and tower crane foundation frame construction with retractable outriggers in all crane capacity classes.
Adaptation of external climbing cage for internal climbing procedure
For the construction of the new 229 meter (751 foot) high Seven World Trade Center in New York, Falcon Steel, a daughter company of Helmark Steel, used specially adapted Link-Belt TG series internal climbing tower cranes beside an external conventional Pecco SN355 climbing crane.
The quickly erected steel structure provided large bays for the two TG cranes. To climb the cranes in a fast and economical manner they were based on a jumping frame with extendable outriggers that span the building bay opening. A conventional external climbing cage is mounted below the upper support beams, again equipped with extendable outriggers.
The crane tower above and below the upper support beams stretches over four floor levels in each way. When the external climbing cage hydraulic ram is operated the whole crane upper, including the crane tower, the upper support beams and climbing cage, are lifted. As soon as the upper support beams are resting on a higher floor level, the hydraulic rams are retracted to let the base crane follow up.
Adaptation of internal climbing devices for external climbing
As high rising building structures become more complex due to architectural freedom, it may even be desired to jump a crane outside the core of the building under construction or alongside large openings that can't be economically spread with a jumping frame.
On several prestigious projects under construction in China, special solutions were found for Favelle Favco tower cranes climbing alongside cores with sets of climbing collars mounted on specially designed outriggers. At first glance the “hanging” cranes look like external climbing cranes. They are jumped, however, in internal climbing mode, with the great benefit that no tower reaching down to the building base is interfering with the construction process below the crane level.
In some cases the building shape calls for a transformation of a conventional internal climbing crane into an external climbing crane with climbing cage. It can be, for example, to top out the building where space is restricted in the roof area. This repositioning of the crane is often associated with a removal from the centre to the edge of the building under construction. In this case the complete crane has to be derigged and rigged at another place on the building. This can be more easily done when a pair of cranes is engaged because then one crane is used as an assist crane.
Internal jumping frame
Creative solutions for internal climbing systems adaptable to upper cranes from different manufacturers have a long tradition in the US. One of the most successful is the 2002 patented flexible climbing device developed by Federated Equipment Company.
This device has already been used for jacking Favco cranes of different sizes, as well as Link-Belt/Cornell tower gantry cranes from the TG range, on prestigious high rise steel projects. The system is applied at, for example, the New Goldmann Sachs headquarters and Freedom Tower developments in New York.
On high rise steel construction projects the bay of a building under construction is normally larger than the cross section of a crane tower system with collars. This means that the floor area of the bay has to be filled up with temporary structures to accommodate the crane tower, which means there is a substantial amount of additional construction material and labor.
In addition, conventional crane lifting systems often require an entire day or even more to jump the crane causing severe down time in the construction process. Federated Equipment developed an improved lifting device in which the crane load is not distributed to horizontal beams of the building so the lifting can be performed rapidly. The system consists of an upper basket, a lower basket and a rectangular lifting frame for jumping the tower. The upper basket and the lifting frame are vertically sliding alongside the tower. The tower is attached to the lower basket that supports a tower crane and sits within a bay, formed by the vertical columns of the building under construction.
The basket has four outriggers with hydraulically operated sliding foot members resting on support stubs attached to the vertical building columns. Each outrigger consist of two arms leading from two edges of the basket to one column of the building bay, allowing best distribution of the forces generated by the crane tower. The lateral and vertical load is distributed vertically to the vertical columns rather than horizontally so no reinforcement of the building structure is needed.
Considering a typical 45 story steel building the savings in steel cost and labor is estimated to be between $500,000 and $1 million. For increased fall protection during operation of the crane and to allow workers to walk on the baskets during climbing operation, a platform fixed with the horizontal arms of the basket can cover the entire building bay.
The crane tower has to be slightly modified. Angle pieces are welded to the mid-points of the diagonal bracings of the crane tower where hydraulic jacks fixed to the upper basket can grip for climbing operation. Climbing is done in two steps. First, using the lifting frame, the upper basket is raised alongside the tower and seated on support stubs at the desired level. Then, using the upper basket as support, as well equipped with outriggers and sliding foot members, the lower basket, including the tower, is raised. By repeating these climbing steps different floor level heights can be used to accommodate the crane. Its main restriction is the free standing tower capacity of the crane. The whole jacking operation is efficiently completed in just a few hours.
Like the outriggers of a mobile crane the lower basket gives enough lateral support so that the upper basket may not be needed when the crane is in operating condition.
At the initial construction stage, therefore, the crane can be installed as a free standing tower, with just the lower basket, before it becomes a climbing crane later on in the construction process. As a further benefit in this condition no concrete foundation for the crane tower is needed. Instead, just the first steel grid of the building under construction is needed, which, in North America, is usually rigged by mobile cranes.
To cope with different shapes of the building bay, variable long outriggers can be rigged at the baskets. Even one arm can be longer than the other three.
A similar climbing device, but rope operated and equipped with a tower integrated lifting column as climbing unit, was engaged at the 212 meter (698 foot) Times Square Tower project in New York by steel erector Canron.