Cranes on construction sites

      

Tower cranes are common sights on construction sites. Such cranes normally have large weights placed on and around their bases, these weights ensure that the centre of mass of the crane and its applied loading lie over its base area and that the centre of mass of the crane is low increasing its stability. Fig. 2-11a shows a typical tower crane on a construction site. Concrete blocks are purposely placed on the base of the crane to lower its centre of mass to keep the crane stable as shown in Fig. 2-11b.