The seismic response of inelastic structures. (1974)
AuthorsSharpe, Richard Deaneshow all
Because of the importance being placed by modern building codes of practice on the need for the deterministic analysis of ductile frames as a means of assessing their ability to withstand severe seismic ground motions, an investigation of the more important factors affecting such analyses has been made. The problems encountered in writing a comprehensive computer program, with which the sensitivity of a two-dimensional inelastic frame can be measured, are dealt with in depth. These extend from that arising from the obvious need to simplify the input data and printed results, to that of the selection of an economic (and sufficiently accurate) numerical integration technique which can be shown to remain stable over a realistic frequency range. The difficulties met in designing a beam-model which will exhibit a moment-curvature relationship that can be satisfactorily tracked, are described and a recommendation made as to which method should be used. The sensitivity of a selection of frames to different aspects of their modelling is investigated in order to provide guidance as to the complexity of modelling that is required for dynamic analyses. In an attempt to correlate the damaging potential of various earthquake accelerograms, so that they may be related to the requirements of modern building codes of practice, a variety of possible scaling criteria were tested. Although no firm conclusions are reached as to which criteria is to be preferred, a series of inelastic analyses are reported, in which the varying effect of different earthquakes can be seen. Finally, two examples of structures whose design benefited by their having deterministic dynamic inelastic analyses performed, are described, together with the computer program used.