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PROCEEDINGS OF THE EIGHTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY
Edited by: B.H.V. Topping, G. Montero and R. Montenegro
On the Dynamic Behaviour of a Singular Geometry Concrete Belfry
S. Ivorra1, F.J. Pallarés2 and M.L. Romero3
1Department of Construction Engineering, University of Alicante, Spain
S. Ivorra, F.J. Pallarés, M.L. Romero, "On the Dynamic Behaviour of a Singular Geometry Concrete Belfry", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Proceedings of the Eighth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 237, 2006. doi:10.4203/ccp.83.237
Keywords: dynamic interaction, bell forces, belltower, natural frequencies.
The church belltower of the Nuestra Sra. del Monte Vedat in Torrente (Valencia, Spain) is of recent construction. The project was designed in 1992 and finally built in 1994. After construction enormous problems were detected originated by the excessive movement of the tower when the bells swung. In this tower the ringing bells rotate in a complete circle and continue in the same sense. They are very balanced and are directly anchored to the tower windows . It is mentioned in the Anglo-Saxon literature as a swing to full circle , and it is characteristic in a large part of Spain. Before the excessive problems were observed, the turns of the bells in this tower were stopped for a period of several years until strengthening of the structure was carried out in 1998. This reinforcement consisted of the introduction of diverse metallic elements in the structure. In spite of this intervention, at the present time the two bigger bells continue without turning because certain movements continue and they can be appreciable when these bells are turning.
The tower has an irregular pentagon section to a height of 17.25 m, starting from this height one of the walls of reinforced concrete continues to the top of the tower. This wall belfry continues to a height of 26.4 m. At half of height of this belfry wall two cantilever beams appear with a length of 2.5 m. The external view of this belfry is similar of a cross. The walls of the whole tower are made of reinforced concrete and they have a thickness of 0.4 m.
Inside this wall belfry, there are several openings to house the six bells of different weights. The two bigger bells are situated in the superior part of the wall belfry, above the cantilever beam, and the other four also in the wall belfry, in the inferior part to the crown. The characteristics of these bells have been experimentally determined by Heyman and Therefall  and Ivorra and Llop .
This paper describes the analysis performed to investigate the phenomenon: the natural frequencies of the tower are determined by experimental techniques, a structural finite element model has been developed and it has been calibrated using the experimental results. Later the horizontal forces generated by swing bells have been evaluated and they are introduced into the finite element analysis. The horizontal forces have determined using the recommendations in references [1,5,6].
Three analyses have been carried out: static lineal analysis, modal analysis, and a time history analysis for each one of the bells of the tower, especially for the case of the two bigger bells, located on the top of the belfry walland consequently with a greater probability of being the most problematic.
The values of the horizontal forces introduced by the big bells are totally inadmissible for this belfry wall. Dynamic interaction between of the tower natural frequencies and horizontal forces generated by bells is very high and the displacements at the top of the belltower are excessive.
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