Seismic protection of the Messina Cathedral Bell Tower through Vibrating Barriers

Seismic protection of heritage structures is an unresolved research problem that not only is a public safety issue but also encompasses the additional constraint of the protection of the artistic value. In this regard non-invasive techniques appear clearly the most appropriate. In this paper the recently proposed non-invasive vibration control device Vibrating Barrier (ViBa) is scrutinized and extended to reduce the seismic vibrations of the Messina Cathedral Bell Tower in Italy. A detailed study is first undertaken to determine a reliable model of the Cathedral and surrounding area. Original drawings and design calculations have been used to develop a pertinent Finite Element model. The seismic action has been modelled as a zero mean Gaussian process compatible with the response spectrum of the site where the Cathedral is built. In order to design the Vibrating Barrier device a reliable simplified discrete model has been derived and calibrated through an identification procedure. Due to the dynamic behaviour of the Bell Tower a novel design strategy accounting for the rotational coupling of the underlying structure-soil-structure interaction problem has been proposed. Interestingly, the influence of the rocking behaviour of the Tower on the performance of the ViBa has been addressed. The efficiency of the ViBa device has been measured through the reduction of the dynamic response in terms of displacements and internal forces. Reduction of the peak displacements greater than 20% has been achieved without modifying the Bell Tower. Challenges in the implementations of the ViBa and its limitations are also discussed.