IN-SITU MEASURED DYNAMIC RESPONSE OF THE BELL TOWER OF AGIOS GERASIMOS IN LIXOURI-KEFALONIA, GREECE AND ITS UTILIZATION IN THE NUMERICAL PREDICTIONS OF ITS EARTHQUAKE RESPONSE

Abstract eng:
The dynamic and earthquake response of the bell tower of Agios Gerasimos, located at the city center of Lixouri in the island of Kefalonia, Greece is examined here. This structure was subjected during the winter of 2014 in an intensive earthquake sequence. The dynamic characteristics of this bell tower were measured in-situ through a series of free vibration tests that were performed following the earthquake sequence. Subsequently the dynamic and earthquake response of the bell tower was numerically simulated employing a 3-D elastic numerical simulation shell elements. The foundation was included in the numerical model assumed to be a mass-less concrete block that is formed by mass-less horizontal slabs and vertical slabs. A number of linear horizontal and vertical links are also employed aimed at representing the resistance of the soil surrounding the foundation block in the x-x (N-S), yy (E-W) and vertical (z-z) directions. The numerical simulation examines the value of the stiffness of these vertical or horizontal links in a parametric way. First, the axial stiffness for all the vertical and horizontal links attains the value of 10000000KN/m that represents a nondeformable soil. Next, the vertical and horizontal links are given a value for their axial stiffness in such a way that the resulting 1st translational E-W (y-y) eigen-frequency is approximately equal to the corresponding value that was measured during the free vibration tests. Then a third case is also examined whereby the stiffness of these links becomes even lower. The obtained numerical results of all these examined cases are presented and discussed. It is demonstrated that the soil – foundation – structure interaction influences the dynamic and earthquake response predictions for this structure quite significantly. It also demonstrates the usefulness of such in-situ testing towards formulating realistic numerical models in order to yield realistic predictions of the dynamic and earthquake response of the examined structures.

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