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Measuring Structural Motion Without Permission

Description: 

The experimental assessment of the modal frequencies of engineering structures is a key step in several seismological applications, such as defining the input for seismic response spectra, calibrating and validating dynamic models, evaluating the effects of interventions or retrofitting of existing structures.

Active testing has given way to more convenient passive approaches. Accelerometers are still the preferred transducers within the engineering community, whereas the seismological community favor geophones, due to their higher sensitivity, which make them more suitable for weak-motion analysis.

More recently, sensors that measure displacements—based either on electromagnetic wave source-to-target travel times or on interferometric techniques—have also begun to be used. These have the advantage of being contactless and capable of investigating a larger portion of a structure from a single acquisition point, at the cost of much larger datasets to be processed.

We will present some unconventional approaches for performing dynamic characterization of structures. First, we will show how the dynamic behavior of many buildings can be identified even in ground-based recordings acquired for completely different purposes. Seismic stations themselves, which are almost always installed inside structures of various sizes, contain information about the dynamic properties of the hosting structure. In the case of large structures—such as viaducts, towers, and wind turbines—their dynamic behavior can be detected even at large distance from the structure. Being able to recognize this contribution is a fundamental step in ground-motion studies.

We will then illustrate how instruments external to seismology, such as standard video cameras, can be employed to assess the modal frequencies of structures. Optical approaches have long been used to study mechanical vibrations in laboratory settings where many variables can be controlled. Here, we apply them to detect the modal frequencies of typical structures under operational conditions. We will explore different processing workflows and discuss their performance.

Session: Earthquake Ground Motions and Structural Response: Emerging Tools and Applications - II

Type: Oral

Date: 4/16/2026

Presentation Time: 11:00 AM (local time)

Presenting Author: Silvia Castellaro

Student Presenter: No

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