Mahmoudabadi - Assistante Professor, Special Structures Dept., Structural Engineering Research Center, International Institute of Earthquake Engineering and Seismology, I.R. Iran

During Firooz Abad-Kojour earthquake (May 28, 2004) and Changureh (Avaj) earthquake (June 22, 2002), the response of a 14-story concrete building in Tehran has been measured by four SSA-2 accelerometers at basement 3, floor 5 and roof level. One accelerometer has been installed at lowest level of building (basement 3), other one at floor 5 and two remaining accelerometers have been installed at roof level. The building has been located about 75 and 225 km of two above mentioned earthquake centers, respectively. Maximum ground acceleration which has been recorded at basement 3 during these two earthquakes are 23.1 and 5.2 gal (cm/sec2), respectively. The records of these accelerometers have been used to extract dominant modal parameters of the building during above two mentioned earthquakes by using a parametric frequency domain identification approach. Modal parameters consist of modal frequencies, modal damping ratios and modal effective participation factors. Finally, identified fundamental modal frequencies in N-S and E-W directions have been compared with corresponding values of related periods obtained from Iranian code of practice for seismic resistant design of buildings.