Numerical Assessment of Cracks on a Freestanding Masonry Minaret

The Minaret of the Sheikh Mutahhar Mosque was constructed in the beginning of sixteenth century. It is located in Diyarbakir, a city with moderate seismicity in Turkey. Although it has survived for five centuries, the tower is seemingly vulnerable to ground movements, because the minaret body simply stands freely on four cylindrical stone columns. A description of this special structure is provided. In recent years significant cracks have developed in two of the main lintels at the base of the minaret. The square cross-section minaret may be used as an ersatz, large-size seismograph, to examine the possible upper limits of seismic action that must have affected it without leading to overturning and stressed it beyond its strength to develop the observed cracks. Seismic response of the minaret is investigated through a numerical model generated using an explicit finite element code. The frictional contact behavior between stone units is included in the model and used to estimate the inherent damping. The 3D nonlinear finite element model results are compared with results of rocking rigid block model. It appears that the amplitude of the ground motion at the site did not exceed 0.15 g during the 500 years life span of the minaret.