Modal analysis of a cable-stayed bridge model using a modified Ibrahim Time domain algorithm

Modal analysis procedures are efficient techniques to identify modal properties of structures. The objective of this work is to conduct a vibration survey of a laboratory cable-stayed bridge model and to develop a systematic method for the extraction of the dynamic characteristics of the bridge model. The proposed method is based on the classical Ibrahim Time Domain (ITD) method and allows directly use the real time acceleration response measured from accelerometers due to ambient excitations. This is a clear advantage over classical ITD method. The feasibility and practicality are examined through a numerical study and an ambient modal testing of the bridge model. The modified method provides a very effective way to identify the dynamical properties of the structure. Modal analysis results shows that the bridge model is characterized by the presence of many closely spaced, coupled modes.