No abstract

A structural damage detection method using uncertain frequency response functions (FRFs) is presented in this article. Structural damage is detected from the changes in FRFs from the original intact state. The measurements are always contaminated by noise, and sufficient data are often difficult to obtain; making it difficult to detect damage with a finite number of data. To surmount this, we introduce hypothesis testing based on the bootstrap method to statistically prevent detection errors due to measurement noise. The proposed method iteratively zooms in on the damaged elements by excluding the elements which were assessed as undamaged from among the damage candidates, step by step. The proposed approach was applied to numerical simulations using a 2D frame structure and its efficiency was confirmed.

A sequence of two strike-slip earthquakes occurred on April 14 and 16, 2016 in the intraplate region of Kyushu Island, Japan, apart from subduction zones, and caused significant damage and disruption to the Kumamoto region. The analyses of regional seismic catalog and available strong motion recordings reveal striking characteristics of the events, such as migrating seismicity, earthquake surface rupture, and major foreshock-mainshock earthquake sequences. To gain valuable lessons from the events, a UK Earthquake Engineering Field Investigation Team (EEFIT) was dispatched to Kumamoto, and earthquake damage surveys were conducted to relate observed earthquake characteristics to building and infrastructure damage caused by the earthquakes. The lessons learnt from the reconnaissance mission have important implications on current seismic design practice regarding the required seismic resistance of structures under multiple shocks and the seismic design of infrastructure subject to large ground deformation. The observations also highlight the consequences of cascading geological hazards on community resilience. To share the gathered damage data widely, geo-tagged photos are organized using Google Earth and the kmz file is made publicly available.

We report a procedure by which structural parameters and input ground motion are identified from measured responses only. We have assumed that the coda of the response time history represents the free vibration response of the structural system. Because the coda is not effected by the input ground motion, we can first identify such structural parameters as the masses, damping coefficients and spring constants from this part of the record. Input ground motion then is estimated from the full record and the identified parameters. The identification and estimation are made with the Kalman filter. To verify the effectiveness of this procedure, we have simulated the responses of a linear, three-degree-of-freedom system for different earthquake inputs and made estimations using the simulated responses as observed records. The estimated accelerograms, the identification of which usually more difficult than the identifications of velocitigrams and displacementgrams, are in good agreement with the recorded ones for the actual earthquakes.