| Research Abstract |
From 2002 to 2003 March :
(1)First of all at the beginning of the year, the directions for the present research were searched towards for sustainable space structures for reticulated domes, cylindrical lattice shells and latticed arches. Damages are expected to members and other related structural elements in the upper structures (space structure), sub-structure (supporting structure) and connection such as shoes between the former two. Depending on the parts to be damaged due to severest earthquakes, structural systems were classified as follows : with respect to the upper structure, (a)(upper elements yielding type) a structural system with members to yield, not buckle, within itself to absorb seismic energy, and (b)(member yielding adjacent to shoe type)a structural system with members to yield adjacent to shoes, and (c)(viscous element type)a structural system with visco-elastic members in addition to ordinary elements, and by focusing on the sub-structure, (d)(buckling restraint me
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mber type)a structural system with buckling restraint members to yield, (e)(shoe yielding type) a structural system with shoes to yield, (f)(foot member yielding type) a structural system with sub column members to yield just above the footing, and (g)(intermediate isolation type) a structural system with intermediate base isolation between the upper and sub structures. All those are expected ductile structural systems to absorb seismic energy by yielding or viscosity, where damaged elements are expected to be repaired or replaced easily just after big earthquakes instead of much strengthening. Judging from the easiness of replacement and element reuse, the types of (b),(c),(d),(e),(f) and (g) excluding (a)are considered appropriate for application to structures. (2)Second, based on the searches, a system for time history response analysis as well as pushover analysis of performance based design were started following the previously accumulated results of researches. Soon after the preparation, (3)design schemes as performance based design for the buckling restraint member type and intermediate isolation type were examined adopting several numerical simulations.
From 2003 to 2004 March :
For each type mentioned above, simulations were repeated to examine if seismic energy can be absorbed within the elements that were assumed to work, how and what amount of energy the elements can absorb and if there are dangers to affect other structural members expected no to yield or buckle. Based on the results, effectiveness of each structure type as damage tolerant design was confirmed and the conditions where each type should preserve were made clear. At the late half of the year, a study was started for 3-D FEM scheme with elasto-plastic super large displacements towards a further research to be used to prove performance as a special hysteresis device called J dampers made SS400 (400N/mm^2), proving the usufulness and continuing still at present.
Based on the researches so far, papers have being submitted actively for publication in journals.
From 2004 to 2005 March :
Further activities of researches have been performed following the precedent years, and the results are begun as submission of papers for publication in journals. At the end of the research period from 2002 to 2004 fiscal years, a further search has been just started for developing the present research project up to more refined and more practical stages. One direction will be a study for two-mode pushover analysis for seismic performance design considering damage tolerant structures, and another one will be a design concept for structures for hospitals that are needed to function even after severest earthquakes. Less
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