| The current seismic design procedures are based on strength and do not account for the duration of strong motion which can influence the damage a structure experiences during an earthquake. A design approach based on energy, on the other hand, takes into consideration the duration of strong motion. In developing an energy-based design approach, one needs an estimate of the earthquake input energy, and its distribution to various structural members. Among the components of earthquake energy, the hysteretic energy is associated with inelastic action and damage. This study examines the influences of the soil and ground motion characteristics (severity, duration, and frequency content) on earthquake input and hysteretic energies as well as their distributions in buildings. The study uses four sets of forty accelerograms each, classified according to soil sites B, C, D, and E of the International Building Code 2003. The distribution of energy is computed for buildings with: fixed base, supplemental damping, and base-isolation.; The study shows that the soil and ground motion characteristics have a major influence on the amount of energy transmitted to a building, but a minor influence on how the energy is distributed through the height. In addition, the structural system influences the amount and distribution of energy in structures. Expressions for estimating the earthquake input and hysteretic energy spectra are proposed and compared to those available in the literature.; A new damage index based on ductility is developed and compared to the Park-Ang index that is used by many investigators. Both indices were used to examine the influences of the ground motion characteristics and structural properties on damage potential. Results indicate that the proposed index correlates strongly with the energy dissipated through inelastic action. The advantages and disadvantages of the strength-based design approach are discussed and a seismic design procedure based on damage is outlined. |
