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

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, which combines a nonlinear finite element model of a building and global acceleration measurements to estimate the time history of seismic response at all degrees of freedom of the model. This includes displacements, element forces, and plastic deformations in all structural members. The estimated seismic response is then used to 1) estimate inter-story drifts and determine the post-earthquake re-occupancy 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 the 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 is 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 post-earthquake damage inspection reports and photographic records. The results demonstrate the accuracy and capability of the proposed framework in the context of a real instrumented building that experienced significant localized structural damage.