For the author, some of the most frequently asked questions about tower crane used in construction are:

How many types of tower crane are commonly used in building and construction projects for tall structures?

How is a tower crane erected?

How can a tower crane climb in pace with the ascending of the building structure?

How the crane is dismantled at the rooftop upon the completion of a construction project?

As most of the major operations in construction, no matter how sophisticated they seem, there is no sophisticated theory or mysterious magic behind. It is mainly a matter of whether you know it or not. To understand the subject, what you need is just to see it or to witness the process. This series of photos are thus specially selected, trying to answer the above questions.

Delivery of tower crane components to site.

Close up of the major components - a standard section of mast, slewing ring, control cabin and the winching machine segment (right upper corner).

Erection of the first section of mast of the tower crane. At the early stage, the crane is free standing on a mass concrete pad foundation. It can "climb" later by disconnecting the mast from the pad when the building structure ascends to a higher altitude.

Onward erection of the main mast.

Placing the slewing ring segment to the top of mast.

Lifting of the cabin module

Lifting Placing of the cabin module. the cabin module

Pre-fabricating of the jib on a cleared location on site. This jib measured more than 25m in length and composed of 4 standard sections. It is almost impossible to have them connected up in the air. The jib will be connected on ground level and lifted to the mast top in one piece for easy and safe erection.

Lifting up of the winching machine segment.

Connecting the winching machine segment onto the central mast section. Due to the heavy mass of the winching machine, together with the addition of precast concrete blocks to the slot at the tip of the platform, this segment usually serves also as a counter weight to balance the lifting action on the jib side.

The most difficult and dangerous part of the crane erection process - the articulating of the main jib, fixing of the tie members, and finally the placing-in of the lifting cables.

The method: for crane of larger size, a smaller tower crane will be erected with the help of the original crane, which is rested or anchored firmly on the newly completed rooftop, and with its weight carefully spread even on the roof structure. The new crane will help to dismantle the original crane and to lower the components down to street level afterward. Upon the completion, a simple derrick-type static crane or a hoisting rod system operated using winching machine will be installed, which serves to dismantle the smaller crane similarly to the original one. The derrick crane or hoisting rod is made of small articulating sections for easy handling and dismantling reasons. This process may be required to repeat once again by a even smaller set of winching equipment if the original crane is a very big one.

The "soon-be-dismantled" crane helps to erect a smaller crane, which will be used to dismantle the original crane afterward. Note that in this photo, the crane is a what it calls "luffing crane". One obvious feature of which is the tiltable jib, that can be slung upward to minimize its turning radius.

The original crane (the red one) and the smaller crane for dismantling the original. Note the footing of the smaller crane composing of layers of standard I-beam sections. Usually, simple shoring system will also be erected underneath the roof slab so that the weight of the crane can be adequately spread and supported.

Sections of the winching equipment being lifted to the roof by the second crane for later dismantling of the second crane.

A simple derrick-type winching equipment being erected. The yellow crane on the background is "second crane" pending for dismantling.

The mast of a 500 ton-m capacity tower crane being mounted and secured by heavy universal beam sections within the shaft of core wall.

Tower crane can be internally or externally mounted. Climbing action can be made using hydraulic lifting of the entire mast, or by extending the length of the mast by inserting additional mast sections as the building structure ascends.

A similarly crane being mounted inside the structural steel frame in "The Center" project.

Detail of mounting of the crane within the structural steel frame inside the "Center" project.

An externally mounted crane used in typical housing project of the Housing Authority

To mount the tower crane securely to the building structure, at least 2 sets of clamping devices that arranged of steel beam sections should be provided to grasp and station the mast of crane. The photo shows clearly the arrangement of the mounting.

The perfect location to position an internally mounted crane is the lift shaft or other structural openings, that have the void already in place as well as they are usually structurally strong enough for the imposed load of crane. However, sometimes it may be required to locate the crane on usual floor slab position as the one shown here. It may be possible subject to additional strengthening provisions and approval of project structural engineer. Note also the reinstatement of the floor slab at the lower floors.

Fitters working inside the lift shaft where the tower crane is mounted preparing for the soon lifting arrangement of the crane.

Close up detail showing the clamping devices and the built-in hydraulic jack system of the crane. The steel bar with rectangular slots is used to transfer the jacking action produce by hydraulic rod, stroke by stroke, to push the crane upward.

A typically external mounted crane used for the construction of the bridge tower for Ting Kau Bridge on the Tsing Yi Island side.

The standard mast module is ready for the insertion into the main mast through the external climbing device.

Close up detail of the main mast, the external climbing device module and the hydraulic jack arrangement.

Line drawing showing the typical construction of a static tower crane with an external climbing device.