β Scribed by Paolo Emilio Pinto
No coin nor oath required. For personal study only.
Methods for seismic reliability assessment are selectively reviewed, on the basis of their capability of providing, in their present form or in their foreseable state of development, a realistic measure of the total risk. Realism starts with description of the seismic input, which must be related to the main parameters of earthquake generation and wave propagation. It then involves structural models, which must be sufficiently accurate to incorporate physical measures of structural performance, to describe the actual sources of uncertainty, and to detect all important modes of failure. Finally, realism implies a degree of complexity of the method and computation which are acceptable to advanced engineering practice. As regards the input, it is argued that properly selected recorded accelerograms (and, in the future, possibly, synthetic accelerograms) satisfy the requirement of realism to a much higher degree than random processes and samples. The consequence of the use of accelerograms is that, whatever risk evaluation method is adopted, simulation is always necessary, in order to take account of sampleβtoβsample variability. Three main categories of method are distinguished: simulationβbased, FORMβbased (First Order Reliability Methods), and responseβsurfaceβbased, although the boundaries between the three are often blurred. A number of different proposals for implementation exist in the literature within each category. A subjective selection has been made of two or three of these proposals for each category, as a means of describing the general approach in more detail and for discussing their essential limitations. The opinion is offered that the subject area of seismic risk assessment still presents great opportunities for development, both of a fundamental and an applied nature. It is encouraging to note that large efforts are being made internationally on both aspects, and that the profession is showing increasing consciousness of the importance of the approach and a willingness to introduce it into common engineering practice.
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