Reconstructing Element-by-Element Dissipated Hysteretic Energy in Instrumented Buildings: Application to the Van Nuys Hotel Testbed

Abstract

The authors propose a seismic monitoring framework for instrumented buildings that employs dissipated energy as a feature for damage detection and localization. The proposed framework employs a nonlinear model-based state observer that combines a nonlinear finite element model of a building and global acceleration measurements to estimate the time history of the seismic response at all of the model’s degrees of freedom. This includes displacements, element forces, and plastic deformations in all structural members. The estimated seismic response is then used to (1) estimate interstory drifts and determine the postearthquake reoccupancy classification of the building based on performance-based criteria, (2) compare the estimated demands with code-based capacity and reconstruct element-by-element demand-to-capacity ratios, and (3) reconstruct element-level normalized energy dissipation and ductility. The outcome of this process is employed for performance-based monitoring, damage detection, and localization in instrumented buildings. The proposed framework is validated using data from the Van Nuys hotel testbed, a seven-story reinforced concrete building instrumented by the California Strong Motion Instrumentation Program (Station 24386). The nonlinear state observer of the building was implemented using a distributed plasticity finite element model and seismic response measurements during the 1992 Big Bear and 1994 Northridge earthquakes. The performance and damage assessment results are compared with the postearthquake damage inspection reports and photographic records. The results demonstrate the accuracy and capability of the proposed framework in the context of a real-world instrumented building that experienced significant localized structural damage.