Brana, Petar, Čulo, Ksenija, Sigmund, Vladimir, William. G. Sullivan, Munir, Ahmad, Dieter, Fichtner, Wilfried, Sauer, Gerald, Weigert, and Thomas, Zerna
The operation of a tower crane is characterized by cycles which occur in a specific order, but do not have a specified time of duration. The undefined time of duration of each transport subprocess is not completely chaotic and arbitrary, so that there is a possibility of estimating when the process will take place, and in turn, prognosing the duration of the cycle. The duration of the transporting cycle can be prognosed by combining analytical relations, proved empirically, with the technics of simulation on the basis of which the modelling of transport processes of tower cranes is made possible. The aim of the structural and quantitative analysis of tower crane transport processes is to examine the nature of the influences affecting the duration of each subprocess and to create the foundation for prognosing the duration of both the subprocess and the entire cycle. The duration of the cycle cannot be calculated by simply adding up the duration of each of the subprocesses because they occur at the same time and in the certain order within one cycle. Tower cranes are in operation for a relatively short period of time in a working shift, so that for example, according to that amounts to only about 30% of the available operational time. Studies have shown that the duration of the state in which cranes wait with loads or on loads is the same of greater than the duration of the state of transporting. The study gives a simulation model for determining the duration of the operating cycles of a tower crane as variable, accidental quantitites.