BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:Critical Excitation Methods for Important Structures - Prof Izuru Takewaki\, Dept of Urban &\; Environmental Engineering\, Kyoto Universi ty DTSTART:20080711T140000Z DTEND:20080711T150000Z UID:TALK12751@talks.cam.ac.uk CONTACT:Zelda Stuck DESCRIPTION:There are various buildings in a city. Each building has its own natural period and its original structural properties. When an earthq uake occurs\, a variety of ground motions are induced in the city. The co mbination of the building natural period with the predominant period of th e induced ground motion may lead to disastrous phenomena in the city. Man y past earthquake observations demonstrated such phenomena repeatedly. On ce a big earthquake occurs\, some building codes are upgraded. However\, it is true that this repetition never resolves all the issues and new seri ous problems occur even recently. In order to overcome this problem\, a n ew paradigm has to be posed. To the author’s knowledge\, the concept of "critical excitation" and the structural design based upon this concept c an become one of such new paradigms. \nEarthquake inputs are uncertain ev en with the present knowledge and it does not appear easy to predict forth coming events precisely both in time-history and frequency contents. For example\, recent near-field ground motions (Northridge 1994\, Kobe 1995\, Turkey 1999 and Chi-Chi\, Taiwan 1999) and the Mexico Michoacan motion 198 5 have some peculiar characteristics unpredictable before their occurrence . It is also true that the civil\, mechanical and aerospace engineering s tructures are often required to be designed for disturbances including inh erent uncertainties due mainly to their "low rate of occurrence". Worst-c ase analysis combined with proper information based on reliable physical d ata is expected to play an important role in avoiding difficulties induced by such uncertainties. Approaches based on the concept of "critical exci tation" seem to be promising.\nThe most critical issue in the seismic resi stant design is the resonance. One of the promising approaches to this ph enomenon is to shift the natural period of the building through seismic co ntrol and to add damping in the building. However it is also true that th e seismic control is under development and more sufficient time is necessa ry to respond to uncertain ground motions.\nIn this talk\, the role of cri tical excitation methods in the design of important structures is discusse d extensively. The problem of critical excitation for time-dependent perf ormance indices is treated first. Then the problem of critical excitation for earthquake input energy is discussed. The application of various cri tical excitation methods to high-rise buildings\, base-isolated buildings\ , nuclear reactor facilities\, etc. will be presented.\n\n LOCATION:Engineering Department - LR6 END:VEVENT END:VCALENDAR