ABSTRACT
In the past years, structural health monitoring (SHM) has been applied to more and more bridges and large buildings, in which environmental and structural parameters are measured to assess the state of the structure. For large structures, such as bridges, tall buildings, and spatial structures, operational modal analysis (OMA) based on ambient vibration is the most practical and efficient method to obtain the modal parameters, which are essential to the assessment of the structure. Modal parameters can be identified by OMA methods based on the vibration information measured via accelerometers placed on the structure. In this chapter, several commonly used OMA methods are reviewed, including frequency domain methods and time domain methods. Based on that, the SHM for several spatial structures are introduced, including the types and numbers of sensors, data analysis methods, and the results. The projects include the Shijiazhuang Yutong International Stadium, a hangar in Xi’an, and a space frame in Xuzhou. The measured results are analyzed and compared with the design value of the structures, which indicate that in practical engineering applications, the frequency domain methods work well enough for the modal frequency, and the stochastic subspace identification (SSI) method is more accurate in frequency, damping, and mode shape. The standard deviations of the damping ratios are much higher than those of the modal frequencies, especially for frequency domain methods. Therefore, the final measured results can take the mean value of a variety of methods. The measured modal parameters have significant difference with the design value for some projects, but the measured values can be used as the base information of the existing projects, which is essential for further monitoring, model updating, damage diagnosis, and state assessment of the structure in the future.
