Analysis of the failure and remedial measures taken after the collapse of a historical bell

Abstract

[EN] This paper describes the collapse analysis of the historical El Jaume bell, cast in 1429, one of the bells in the Cathedral of Valencia's Micalet bell tower (Spain). In 1992 the yoke was completely restored and given a new steel axis. The failure occurred when the bells were being rung on Christmas Day 2014, fortunately without any casualties. After several field visits to assess the damage and failure "in situ", a diagnosis was made of the causes of the failure. The diagnosis was the result of (1) a detailed visual inspection, (2) a metallographic and fractographic analysis of the fractured steel axis, (3) a fatigue damage analysis by finite element modelling software and (4) an estimation of the bell's remaining fatigue life cycle using Wholer S-N curves. In view of the results obtained it was concluded that the fatigue life cycle should have been reached between 300,000 and 400,000 cycles, while the failure occurred at 346,500 cycles. Although these elements are usually designed to not fail during its life, they can sometimes suffer cracks during cyclic ringing. One of the main causes of the fatigue failure was the incorrect design of the steel gudgeon, which produced a high stress concentration and drastically reduced the fatigue strength at 10(6) cycles. The paper also describes the remedial measures taken to avoid fatigue failure in the other bells and the lessons that have been learned from the experience.