modal parameter identification using ambient vibration testing with introducing a new software

the ambient vibration measurement is a kind of output data-only dynamic testing where the traffics and winds are used as agents responsible for natural or environmental excitation. therefore an experimental modal analysis procedure for ambient vibration testing needs to base itself on output-only data. the modal analysis involving output-only measurements present a challenge that requires the use of special modal identification technique, which can deal with very small magnitude of ambient vibration contaminated by noise. two complementary modal analysis methods are implemented. they are rather simple peak picking (pp) method in frequency domain and more advanced stochastic subspace identification (ssi) method in time domain. according to these methods graphical user interface (gui) software developed in matlab. this program is called sip and can be used in modal parameter identification of large civil structures such as bridges and towers. this paper presents the application of ambient vibration testing and experimental modal analysis on large civil engineering structures and also gives brief review of program. also modal parameters of the babolsar arch steel bridge are extracted using sip and ambient vibration data from dynamic test carried out on this bridge.