No tower head and draw bar are obvious features of topless tower crane. Compared with topkit tower cranes (with tower head, draw bar), forces and connection types of topless tower cranes are different. After installing, in service or out of service, stress state of hoisting jib and balanced jib upper and lower chords keeps the same, upper chord being pulled, lower chord being pressed, no effect of repeated press, its mechanical model is single and simple. Because of this, connection designing of topless tower crane is so simple, is convenient to mantle and dismantle the sections quickly.
Most of topless tower cranes apply regular triangle the space truss structure. Upper chord depends on pin shaft link bearing pulling force, lower chord depends on end faces of joint bearing pressure, then the connection of lower chord is very simple, can only depends on two positioning locking pins. When install, can firstly joint the upper hinge pins, then fall the jibs, two positioning locking pins prepared, at last install the bolts. One big hinge pins of upper chord joint jib sections, saving time, which is one obvious feature of topless tower crane. Potain, Liebherr, Terex and Kroll companies have started to produce topless tower cranes, that make topless tower cranes more and more popular.
It reduces the requirement of hoisting machineries that used to mantle and dismantle tower cranes. Because topless tower cranes don’t have tower head, small element mass, lower installing height, the installing height can be lower 10m than similar topkit tower cranes. When install hoisting jibs of topkit tower cranes, it has to be finished on the ground, jointing all jibs and draw bars firstly and then hoisting completely, which needs large loading capacity and high hoisting height. Because after jointing the hinge pins of end jib, then raising the draw bars, so it is easy to appear safety accidents, but topless tower cranes don’t have the problem. Hoisting jibs of topless tower cranes usually have 4m, 5m or 10m. For example, if 50m hoisting jib, its max. element mass is 1/5 of total weight of hoisting jib, that can save mantling and dismantling fees.