Mottarone cable car, Morandi bridge consultant: “You need a tac on the rope”

The truth takes time, but the technological tools are able to provide, with a rather high probability, an answer on the causes of the tragedy of the Mottarone cable car. Gianpaolo Rosati, professor of construction techniques at the Milan Polytechnic and consultant in the story of the collapse of the Morandi Bridge in Genoa, is convinced of this. The scene on the mountain overlooking Lake Maggiore shows a destroyed cabin – in which 14 people lost their lives – but in the impact first on the ground and then against a tree trunk, the trolley and the coupling beam resisted because ” of resistant steel and therefore with the means of diagnostics, but also on sight, you can have many answers “. In particular, he explains to Adnkronos, “an ‘industrial tac’ can be made on the ends of the rope, that is a tomography in which with high intensity X-rays – with a resolving power of even a thousandth of a millimeter – it is possible to distinguish whether the metal is or is not oxidized and if the failure occurred due to fatigue in the material “. One of the most quoted hypotheses among experts is that the blocked emergency braking system has intervened several times in an anomalous way, overloading the rope that has weakened until it breaks in the most delicate point, the ‘fused head’, where the cable hooks the trolley. and where “it may be more difficult to understand what is happening, because lead shields the magnetometric control system”. If lightning is a discarded hypothesis, “it cannot be excluded, however, that there has been an overlapping of the ropes: it is It is possible in a stretch of counter-slope that the wheels of the trolley cut the crossed rope. It has already happened “, explains the engineer. It is from the state of the rope at the breaking point, if cut cleanly or frayed, that we can therefore begin to exclude some hypotheses. Neglect has often accompanied the latest disasters in Italy, “maintenance responds to precise rules: in the manuals – he stresses engineer Rosati – it is established after how many hours of plant work it is necessary to intervene, for example in the rope lift when the rope has passed a certain number of cycles it must be replaced, regardless of its appearance. Otherwise safety is at stake “. What is forgotten is that “ropes, machines, bridges have a term life, another ignored aspect is that no matter how hard we work to reduce the probability of collapse of an element to zero, a probability that the rope breaks it always exists and an engineer cannot say the opposite. “Now all that remains is to give the consultants the right time to study. “The mistake that can be made is to focus attention only on one cause because it has more effect. It is probable that we will arrive at a list of the most probable causes and contributing causes, but it takes an adequate time which for the Morandi Bridge was two and a half years given the amount of documents to be examined and tests to be carried out. It is not only necessary to examine the final moment of the collapse, but to go back along the history of the cable car because there could be hidden eventualities, malfunctions or bad initial designs which in any case, even if distantly, could have reflections on the tragedy “. The elements to look at are not only the broken rope or the braking system, but for example also” the hauling winch and the mechanical systems that, due to malfunctioning, may have damaged the rope. It is the evaluation of all these aspects that allows us to reach plausible conclusions. It is a very delicate situation, it is right to make all possible hypotheses to reach it diagnoses to identify the most probable causes “, concludes the engineer Rosati.

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