Dissipated hysteretic energy reconstruction for high-resolution seismic monitoring of instrumented buildings

This paper proposes a high-resolution seismic monitoring framework that employs dissipated energy as a feature for damage detection and localization in instrumented building structures. The the methodology consists of (1) implementing a nonlinear state observer to reconstruct the dynamic response at all degrees of freedom (DoF) of a structural model, (2) employing the reconstructed response to estimate element-by-element forces and displacements, and (3) using estimated displacement, forces, and constitutive laws to estimate element-level dissipated energy. The main advantages of the proposed energy-based approach are that i) the proposed feature is physically meaningful and correlates well with the level of cyclic damage experienced during strong earthquakes, ii) dissipated energy can be reconstructed from element-level stress-strain fields that can be estimated from global acceleration measurements, and (iii) dissipated energy can be calibrated using experimental data. The effectiveness of the proposed energy-based seismic monitoring framework is investigated using data from the Van Nuys hotel tested, a seven-story reinforced concrete (RC) building instrumented by the California Strong Motion Instrumentation (CSMIP) Program (Station 24386). The Van Nuys building experienced insignificant structural and mostly nonstructural damage during the 1992 Big Bear earthquake. Two years later, the building was severely damaged during the 1994 Northridge earthquake, in which localized damage occurred in five of the nine columns on the fourth story (between floors four and five) of the south longitudinal frame.