Ambient vibration tools to validate the rigid diaphragm assumption in the seismic assessment of buildings

Abstract

SummaryVibration tests are encountering a growing success in earthquake engineering as a valuable tool for the seismic assessment of buildings. Ambient vibration measurements, in particular, offer reliable support for the updating of mechanical models, as well as the enhancement of seismic mitigation strategies for existing buildings. In this respect, the common description of the floor diaphragms as planar rigid bodies tends to oversimplify the actual mechanical behaviour of some traditional structural solutions, especially in masonry buildings. This assumption can be violated even in modern concrete and steel buildings due to inadequate design, poor manufacturing, or damage. The paper addresses the mathematical validation of the rigid diaphragm simplification using vibration measurements. To this purpose, a model‐based inverse kinematic problem is stated and solved to discriminate the in‐plane rigid motion and the angular deformation time histories from vibration data. Simple formulas, leveraging the approximate solution in the case of problem under‐determinacy, exploit the spectral content of vibration data to discuss the diaphragm deformability. Natural modes exhibiting different (rigid, quasi‐rigid, or nonrigid) diaphragm behaviour are distinguishable by comparing the power spectral densities of the rigid motion and angular deformation. Modes of pure floor deformability can also be identified. The influence of adverse testing conditions is discussed through pseudo‐experimental data simulating the dynamic response of a simple frame structure. As a complementary contribution, the procedure effectiveness is experimentally verified by analysing vibration data related to, first, laboratory tests on a scaled concrete‐steel frame and, finally, full‐scale tests on a masonry building.

Postseismic Survey of a Historic Masonry Tower and Monitoring of Its Dynamic Behavior in the Aftermath of Le Teil Earthquake (Ardèche, France)

“…The concern is thus even more acute for cultural heritage buildings. Conducting ambient vibration measurements has proved to be a valuable tool to deepen the knowledge on their global dynamic behaviour, develop more realistic numerical models (Sivori et al, 2020), improve the seismic response predictions and support the decisionmaking (Ercan, 2018;Reuland et al, 2019) while limiting our imprint on those vulnerable structures. The Mw 4.9 Le Teil earthquake, i.e.…”

A methodological framework to relate the earthquake-induced frequency reduction to structural damage in masonry buildings

“…This experimental technique, thanks to its non-destructive and non-invasive characteristics, is today increasingly employed to support the seismic analysis of existing structures. The knowledge of the experimental modal parameters, which reflects the actual operative condition of the structure, plays a primary role in the formulation (Michel et al 2008;Spina et al 2019), validation andupdating (Mottershead andFriswell 1993;De Sortis et al 2005;Snoj et al 2013;Foti et al 2014;Sivori et al 2020;Cattari et al 2021b;Degli Abbati et al 2021;Ponte et al 2021) of experimental and mechanical models, significantly improving the robustness of seismic predictions. The employment of ambient vibrations, in particular, is extremely valuable for structural health assessment, often in the form of continuous monitoring systems.…”

Calibration of Numerical Models to Support Shm: The Consoli Palace of Gubbio, Italy

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