Authors: Francisco Castro, Nuno Viriato Ramos, Francisco Queirós de Melo, Pedro Moreira, Mário Vaz.

The failure of a large tower crane can cause high economic losses and serious injuries or fatalities, that’s why it’s extremely important to identify, not only the causes of its collapse for the attribution of responsibilities, but also and specially focusing on the prevention of new disasters. This paper aims to study and investigate the main causes of the accident and its reconstruction by sequenced collapse stages. Static and dynamic computational simulations were performed to understand the main changes of the structure dynamic behavior due to the height increasing and eventual material changes, which was not contemplated in the manual. It was possible to conclude that the main cause for the accident was due to the excitation of natural frequencies of the structure associated to a pendulum effect of the suspended loads. The changes in the flexibility of the structure due to the increase in height and its dynamic interaction with the oscillations of the suspended load are presented and discussed.

Francisco Castro, Nuno Viriato Ramos, Francisco Queirós de Melo, Pedro Moreira, Mário Vaz.