A completely new approach to the interpretation of seismic test results has been implemented at LNEC Lisbon, using research performed there at JRC Ispra. The research was divided into three parts:
- Improvement of data transfer protocols between data acquisition systems and post-processing computers.
- Computer implementation of numerical techniques for system identification.
- Trial applications to ongoing seismic tests.
Through the first research part, an almost online assessment of data acquired during shaking table tests is possible; this increases the accessibility of the facility to external users. The software developments for the second research part - system identification techniques were in the object-orientated language LabView, which is compatible with the new LNEC DACE system of the first part above. A feature of the new procedures is the ability to use existing software libraries for structural analysis, signal processing and system ID. Based on the Ibrahim Time Domain Method, one of the features of the new procedure is the ability to obtain the dynamic characterisation of structural properties using the final decay motions at the end of the input. The trial applications referred to in the third research part were conducted in collaboration with EERC Bristol on a specially designed test-piece, which exhibited pronounced non-linear behaviour. Two principal results emerged:
- It is possible to obtain a seismic vulnerability assessment by testing a single test-piece, rather than the expensive alternative of using virgin test-pieces for each level of excitation.
- Bayesian inference strategies can be used to update fragility, on the basis of prior knowledge, plus data from experimental tests.