A MODEL FOR DYNAMIC ANALYSIAS OF SLENDER TOWERS MADE OF NO TENSION MATERIAL

In this paper, a model is presented to analyse transverse vibrations of masonry slender structures such as ancient isolate towers and bell-towers. This type of structure, with simple geometry and flexural behaviour, have been modeled as continuous cantilever beams with hollow rectangular cross-section, assuming the material’s no resistance to tension. Developing the model has requested to define a non-linear constitutive equation for hollow rectangular cross-section beams, that gives generalized stress as a function of strain ones. Due to non-linear behaviour, coupling between transverse and axial motion occurs. Therefore, in order to obtain a numerical model simple enough to perform a large amount of parametric analysis, a further simplification has been made. By assuming the axial force known, a non-linear constitutive law expressing the bending moment as a function of the beam curvature only has been developed, so that transverse motion can be uncoupled from the axial one. Some examples presented evidence the difference in dynamic response obtained by means of the proposed model with respect to results from linear elastic models, that may be very consistent even qualitatively especially with regard to some dynamic phenomena such as resonance.