Structural Analysis of Gradačac Clock Tower Aiming Towards Intervention in Preserving Authenticity

Old masonry towers, in all their variety – be it a bell tower, a city tower, clock tower, inhabited residential towers, and/or guard/watchtowers – can be found all around the world representing typical urban centre feature, and in some cases –they are the countryside panorama landmark. Statics analysis and calculation are the first steps towards engineering interventions on cultural and historical heritage buildings. In the structural analysis of clock towers, the typical critical points and places where crucial damages that could lead to the collapse, are expected are in the top sections of the building - where the oscillation amplitude reaches its maximal value. Effect on building structure is observed concerning the oscillation frequency and building’s own frequency and energy, which can explain why minaret towers and high slim towers, in some cases, can better withstand earthquakes than extremely rigid buildings; given that the resonance, low-quality materials and other factors can lead to the vulnerability of a building structure. This type of building is designed on a simple, regular shape ground plan, or, in other words, the towers have a symmetrical ground plan and uniformly distributed mass and height. The second statement provides that, depending on building materials used and the cross-section dimensions, towers can be very heavy, which can cause the appearance of significant inertia forces during earthquake oscillations. If there’s mass eccentricity, the horizontal loads could tip the building over. Gradačac clock tower’s load-bearing structural walls are built with masonry stone blocks. The vertical loads are, via slabs and wooden beams, conducted to the walls and down to the foundations. Foundation structure consists of a slab, 80cm thick, positioned at -8.25m which sits on a well-compacted layer of soil. Wooden staircases are used for vertical transportation between storeys. Structural analysis calculation is based on a 3D model of a building and is performed by using the finite elements method (FEM) in Tower calculation software. The requirements for the authenticity in preservation actions imply that the interpretation and the presentation must correlate with basic authenticity principles, in compliance to Nara document (ICOMOS, 1994), protecting cultural values, from both – the hazardous influences of intrusive infrastructure and load of visitors, and incorrect and inappropriate interpretations.