Document Type : Research Paper
Civil Engineering department, Islamic Azad University, Langarud Branch
Structures dynamic characteristics including natural periods, mode shapes and damping ratios are the most important factors of the structure's response to earthquakes. Numerical models used to determine the dynamic characteristics of structures are usually based on simple assumptions. The effects of non-structural components such as infill walls and also the soil structure interaction effects are not considered, as well as the damping rate in the structure depends on the materials consumed and the construction methods that can be measured only by field testing on the structure. In this research, forced vibration test was utilized to determine the dynamic characteristics of a six-roof building located at Rasht's Motahari Avenue. In this test, an exciter was placed on the 5th floor near the center of mass of the floor and the structure was vibrated at specific frequencies. The structure response was recorded by accelerometers and the data obtained from the experiments were analyzed by the SeismoSignal software. The dynamic characteristics of the structure, such as period and main frequencies, were obtained in both directions, as well as the damping and torsion of 5th floor. The results obtained based on forced vibration testing were compared with the empirical values of the Iranian Code 2800 and indicated that the main period obtained by forced vibration test on the actual structure is less than the calculated period according to the Code 2800. In addition, the amount of damping coefficient obtained the test was also less than the amount suggestion in the Code 2800.