An energy method for the analysis of structures subjected to earthquakes

Work toward developing a simple method for the aseismic design of structures considering energy dissipation as the prime design parameter is reported. Viscous damping is used to represent the non-structural energy dissipating elements in the system, and hysteretic energy dissipation is considered explicitly. A detailed parametric study of the energy dissipation characteristics of single degree of freedom systems is reported first. Here the amount of energy dissipated by both hysteretic and viscous damping mechanisms in each system is determined for various ground motions, viscous damping values, system strengths etc. The results of this study are presented in the form of spectra, relating total energy dissipated, and energy distribution between mechanisms to known system properties. The results and insights gained from the parametric study are incorporated into a design method which accounts explicitly for energy dissipation. The inclusion of a system strength parameter in the input of the proposed method is found to he most useful in terms of the limit state philosophy employed in the most recent editions of building codes. Also if special damping devices are to he built into the structure, this method will facilitate such design. Finally a preliminary study of the energy dissipation characteristics of multi-degree of freedom systems is reported. Here the distribution of energy dissipated by viscous damping and hysteresis, together with the location of the effective dissipating mechanisms within the structure, is studied. In particular the possibility of extrapolation from single degree of freedom spectra to the multi-degree of freedom systems is investigated and shown to give encouraging results.Applied Science, Faculty ofCivil Engineering, Department ofGraduat