In order to build the super tall skyscrapers of today such as the Wilshire Grand Center in Los Angeles, huge tower cranes are used. Tower cranes are capable of lifting very heavy loads of steel, concrete, generators and other building materials and can be erected to grow taller as the construction project moves upward.
Before a tower crane is ready to use, it needs to be stabilized at the jobsite. The process entails building a concrete pad with large anchor bolts embedded into the concrete that secures the base of the crane. Once a tower crane reaches its maximum height, it can be tied to the side of the structure with steel collars and moved upward as a project demands.
The gears and motor for the crane are contained in the slewing unit that is attached to the mast and which allows the crane to rotate. On top of that is the long jib that is used to lift the heavy materials as well as the counter-jib that works as a counter-weight to keep the crane balanced. The crane operator may control the unit from the ground or in a cab that is on top of the tower.
The tower crane mast is a steel triangular lattice structure that is constructed of vertebras generally 10 square feet in size. Once a crane has been fastened to the exterior of the building or in some cases to the interior and needs to be raised higher, the process is started to add new pieces. A climbing frame or metal sheath that sits between the slewing unit and the top of the tower is used to temporarily support that section of the mast while the jib moves a new segment into the space. Once the new piece is bolted down, the climbing tower then moves higher up along the mast ready for the process to begin again.
According to Wikipedia, typically the maximum unsupported height of a tower crane is 265 feet and the maximum reach of the jib is 230 feet. It has a maximum lifting strength of 19.8 tons.
Conco’s team of professional concrete contractors in the Portland area brings the highest level of integrity and principles to each project from pre-construction to finish. With the rapidly growing construction market, Conco is taking an active role in the Portland area with our expansion of high-quality commercial concrete services.