Tower crane is the most common crane in construction sites It is one of the fixed cranes' type. It consists of two main parts, the mast of the crane is fixed through the base to the ground on a concrete slab or on the building sides. The upper part which is the horizontal jib is the part used for lifting. The upper jib is divided in two parts, one long and the other is short. The long part is responsible for lifting and moving weights. The short jib is used for keeping balance of the crane. This short part is loaded with concrete blocks or steel weights to keep the stability on both sides of the jib. The crane uses wire ropes for both lifting and bracing weights. These ropes are connected to electric engine. There is operator chamber for operating the whole crane. This chamber can be at the top of the mast under the horizontal jib or attached to the turntable.
Some cranes do not have the operator cab installed on it because it's operated through a radio remote control from the ground. For holding the lifted weights, the crane use hook which is hooked to the weights with the workers help. The operator in the cab must communicate with the men on the ground to know when and how to lift the weights.
This crane reaches the construction site in pieces then it is assembled by the aid of telescopic crane . when the height needed is bigger than the telescopic crane lifting range , a specific type of tower crane is used . this specific type is called self erecting crane. The tower crane must be fixed to the building walls when the height exceeds 80 meters.
