Measurements of point rotations in full-scale structures during earthquake excitation do not exist at present, but average rotations can be computed from pairs of parallel transducers. The examples presented illustrate rotations in the range from 10-6 to 10-3 rad and angular accelerations from 10-4 to 10-1 rad/sec2. Measurements of rotations in the structures for excitation by microtremors are also described. It is argued that recording the rotational components of motion contributes significantly to the overall volume and quality of information. It is recommended that the development and deployment of instruments to measure rotational components of motion in free-field conditions and in full-scale structures will open a new frontier for advanced experimental identification of structural properties and for structural health monitoring.

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