EVALUATION OF DYNAMIC CHARACTERISTICS OF 19-STORY ASYMMETRIC STEEL BUILDING BY AMBIENT VIBRATION TESTS

摘要

In order to investigate the dynamic properties of asymrnetriC steel building with semi-joints connections．Ambient vibration tests are camed out on all asymmetric steel building constructed in the Tehran mega cit．The purpose of this work is to demonstrate a unified procedure for determining the natural frequencies．Modal damping ratios and modal shapes of the structure from its ambient vibration data．Fourier amplitude spectra have been calculated from several intervals of a 40 minutes period of ambient vibration record．Measurements made from the ambient vibration records show tllat the first-mode frequencies of horizontal vibration were 0．73 Hz on E-W direction，0．78 Hz on N- S direction and the first tensional vibration frequency was 1．66 Hz and damping ratio for first mode in E-W and N-S directions were 0．047．The results obtained from tests，were compared to mathematical model of the building．