An Assessment of the Atranos Castle Tower Remains` seismic response and recommendations towards its protection

Atranos Castle is an early Byzantine heritage founded by the emperor Hadrianus in the second century in Orhaneli, a district south of Bursa with mountainous geography. Two towers of the castle survived in partial to date. About 5m long main wall foundation and two more towers’ base were also identified during field study. The survey of the castle remains was done by use of a laser scanner and drone to reveal its disappearing cultural and archeological value. This partially collapsed tower has a partially circular shape in plan. Voids within the masonry body and early findings of the wood remnants in these holes reveal the existence of the bond beams. There were horizontally placed wooden bond beams within the tower walls at several levels in the original construction. The main purpose of these bond beams is to provide in-plane and out-of-plane stabilization of these masonry walls. The voids left after decayed wooden bond beams create weaknesses, such as stress concentration around the holes and a decrease in buckling resistance. A simplified finite element model of one of the partially collapsed towers is prepared and a parametric study is performed. Effects of the voids are examined and filling the voids with a mortar, modulus of elasticity of mortar close to the masonry wall, improved the response of the structure. As a minimum intervention approach to limit further degradation, before any archaeological excavation program starts on the site, mortar fill to the existing bond beam voids is proposed.