Assessment of Vulnerability and Dynamic Characteristics of a Historical Building Using Microtremor Measurements

Microtremor measurement is a precise and applicable technique for evaluating structural dynamic characteristics and vulnerability index of historical buildings. in this research,a historical citadel in iran has been considered. karim khan citadel (arg-e karim khan) is a huge masonry structure,which has been built in the seventeenth century in shiraz,iran. the plan of this building has a rectangular shape and has a circular tower in each corner. the height of each three-story circular tower is 14 m,and the height of walls between each of the two towers is 12 m. one of these towers has been swerved,and for preventing its collapse,concrete was injected to the foundation of this tower. to study seismic behavior and vulnerability of the swerved tower and compare it with other straight tower,microtremor measurements were performed. measurements were done on the center of each tower and its basement simultaneously. for determining natural frequency and damping ratio of each tower,floor spectral ratio and random decrement method were used,respectively. results show that the natural frequency and damping ratio of the swerved tower are 1.9 hz and 1.55 %,while dynamic parameters of the straight tower are 2.12 hz and 3.86 %,respectively. in addition,the towers frequencies are very different to the site frequency (4.18 hz); therefore,the resonance phenomenon is not probable. in addition,the vulnerability indexes of the swerved and straight towers were calculated 131.31 and 76.9,respectively,which shows that the swerved tower is more vulnerable. © 2016,iran university of science and technology.