Noncontact Operational Modal Analysis of a High-Rise Building Based on an Interferometric Radar System and Combined Modal Estimation Scheme

Abstract

The dynamic characteristics of large-scale civil structures are generally evaluated by performing operational modal analysis based on ambient vibration records measured by contact sensors, e.g., accelerometers. However, owing to accessibility restrictions, it is sometimes inconvenient to conduct dynamic response measurements by contact sensors. Therefore, there is a need to adopt noncontact measurement technologies for monitoring the dynamic performance of civil structures. On the other hand, only response records are available for operational modal analysis on account of the unknown nature of ambient excitations, which may lead to uncertainties in modal estimates, particularly damping estimates. In this regard, this paper adopts a combined method consisting of modal decoupling, natural excitation technology, and an eigensystem realization algorithm to perform high-accuracy modal identification with uncertainty quantification. Through numerical simulation study of a frame structure, the accuracy and effectiveness of the combined method for identifying structural modal parameters are verified. Then, taking advantage of noncontact simultaneous multipoint measurements by an interferometric radar system and the combined modal estimation scheme, the noncontact operational modal analysis strategy is utilized to evaluate structural dynamic characteristics of a supertall building after experiencing a sudden vibration event that attracted considerable concern from the public. The purpose of this study is to provide a practical and reliable means of conducting modal estimation with uncertainty quantification from a single measurement and suggest a noncontact modal analysis strategy for structures with difficulty installing contact sensors.