Assessment of seismic structure stability
One method currently used for the determination of the seismic vulnerability of structures is that of the shaking tables. Using this method, the model to be tested is fixed to a platform to which a motion representative of past seismic events is applied. The test has the advantage of being dynamically similar to a real earthquake, however it has two severe drawbacks. Firstly, the amount of energy needed to move the structure is so large that only reduced scale models can be tested. Such reduced models however are not fully representative of real structures. Secondly, the degradation behaviour of the structure cannot be followed accurately in real time with sufficient accuracy. In order to improve this model, three areas were researched. The first of these examined data transfer between the data acquisition systems used and the post-processing computers. A data assessment method was developed which is virtually on-line. This improves the existing method by allowing the degradation behaviour of the structure to be monitored almost in real time, in this way giving more accurate results. It also increases the accessibility of the system for users. In addition, a new software has been developed which enables the use of existing library software for structural analyses and system processing. One of the features of this software is the ability to obtain a dynamic characterisation of structural properties using final decay motions. Finally, trial applications were examined based on a specially designed test-piece. Using this test piece, seismic assessment can be carried out for each level of seismic activity. Until now, a new model has been required for each different level of excitation. This will allow shaking table operators to make more efficient use of their facilities, since seismic vulnerability can now be assessed using a single test piece, and the expense of new models for every test is removed. This research is of value not only to shaking table laboratories, but also to specialist firms and researchers who are involved in the dynamic testing of structures such as buildings, bridges and supply systems.
