Damage Identification Analyses of a Historic Masonry Structure in T-F Domain

Abstract

Fatih mosque, a landmark structure in Istanbul, has suffered structural damage during 1999 Kocaeli earthquake. Using spectral, time-domain (OKID/ERA for SISO and MIMO models) and T-F domain ( WT, HHT ) techniques on ambient vibrations, damage identification has been performed. Results of parametric and spectral analyses indicate close global peaks. Northwest arch ( O 3 ) that was expected to move in harmony with other arches cannot display such a consistent behavior and produces additional local frequency at 24Hz due to disintegrated stones around the crown. Southeast arch ( O 1 ) also has comparable damage producing another locality at 38Hz. Extending linear approaches into nonl inear-nonstationary methods, WT and HHT improved the results in the temporal-frequency energy distribution. Estimated individual and global structural behavior are consistent with visually inspected damage states for O 3 and O 1 . On a global scale, damage additionally generates significant nonstationarity. D ecompositions in WT and HHT show the capability of identifying nonlinear-nonstationary process hidden in the data. T-F analysis detects and localizes any anomalous system behavior and can adequately capture the dynamical behavior of damage in any instrumented part of the structure at any particular time epoch. For historical masonry structures with vulnerable components like large central dome and arches that have low redundancy, there is a need to develop automatic signal/image processing through image processing, machine vision, and pattern recognition for early diagnosis and prognosis for warning of gradually emerging structural degradations.