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Author(s): | P Khashaee; B Mohraz; Fahim Sadek; Hai S. Lew; John L. Gross; |
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Title: | Distribution of Earthquake Input Energy in Structures |

Published: | January 01, 2003 |

Abstract: | In developing an energy-based design approach and assessing the damage potential of structures, one must know the distribution of earthquake input energy among energy components: kinetic, elastic strain, hysteretic, and damping. This report examines the influences of the ground motion characteristics: intensity, frequency content, and duration of strong motion and the structural properties: ductility, damping, and hysteretic behavior on the distribution of input energy for a one- and a five-story building using 20 accelerograms, ten with short and ten with long duration of strong motion. Results indicate that for certain damping ratios, ductility has a significant influence on input energy and its distribution among energy components in a structure. For a given ductility ratio, small damping ratio (less than 5%) has a minor effect on input energy, but a major influence on the energy distribution. Damping ratios larger than 5% have a significant influence on the input energy and its distribution. Three energy ratios that relate to hysteretic energy were computed: the maximum ratio of hysteretic to input energy (E_{h}/E_{ir})_{m}, the ratio of the maximum hysteretic energy to the maximum input energy E_{hm}/E_{irm}, and the equivalent number of yield excursions N_{eq} = E_{hm}/(F_{y}, Up) where F_{y} is the yield strength, and Up is the plastic deformation. It is found that (E_{h}/E_{ir} reflect the energy demand for the entire duration of accelerogram. The study shows that (E_{h}/E_{ir}) m is independent of the duration of strong motion and period of structure; however, E_{hm}/E_{irm} is independent of both only for periods less then 1 s. Results indicate that as the duration becomes longer the equivalent number of yield excursions N_{eq} increases indicating more structural damage. The influence of ground motion characteristics and structural properties on the distribution of energy parameters for a five-story building with fixed-base, base-isolation, supplemental damping and semi-active control are examined using the 20 accelerograms. The results show that: 1) the distribution of energy through the height of the building is mostly independent of the frequency content and the duration of strong motion, 2) base-isolation, supplemental damping, and semi-active control reduce the damage potential by reducing the input and hysteretic energy demands and have significant influences on the distribution of energy through the height of the building. |

Citation: | NIST Interagency/Internal Report (NISTIR) - 6903 |

Keywords: | building technology,design spectra,earthquake energy,earthquake engineering,structural engineering |

Research Areas: | Building and Fire Research |

PDF version: | Click here to retrieve PDF version of paper (3MB) |