Tsuneo Katayama

Earthquake damage estimation and decision analysis for emergency shut-off of city gas networks using fuzzy set theory☆

Abstract Earthquake damage estimation for lifelines can be used for many purposes, for example, planning repair works or simulating network recovery. For gas networks, however, the issue is more crucial, as secondary disasters due to leaks are possible. If necessary, the gas supply should be interrupted in heavily-damaged areas. Therefore, emergency shut-off decision is vital and earthquake damage estimation can be effectively used for a more reliable and swift decision-making. The system proposed in this paper uses fuzzy set theory to formalize knowledge acquired from experience and assess earthquake damage from ground conditions and ground motion characteristics. The results are obtained as fuzzy damage indices. Fuzzy decision analysis is then utilized to transform this imprecise information into a clear-cut decision on whether to cut or maintain the gas supply in a given area of the network.

Use of dense array data in the determination of engineering properties of strong motions

Abstract A dense seismometer array in Chiba Experiment Station of the Institute of Industrial Science, University of Tokyo, was introduced including its complementary observation system for measuring soil and buried pipe strains. By using the dense array data, the variation of peak accelerations within a small area was examined. It was conclusively found that the axial pipe strain is almost equal to the surrounding soil strain in the pipe direction. The soil strains evaluated from dense array data were generally in good agreement with the directly measured soil strains and pipe strains even for a small finite element if the original accelerograms are processed through proper filters. For an incident wave of dominantly shear type, the pipe strain was found to be small, namely the pipe strain measured in 10−6 being only 0.15–0.30 times the peak acceleration measured in cm/s2.

Soil-structure interaction analysis of the Hualien containment model

This paper presents results from forced vibration tests, microtremor observations and earthquake response analysis of a nuclear reactor containment model constructed on stiff soil in Hualien, Taiwan. The dynamic behavior of the soil-structure system is simulated successfully with two numerical models: a sway-rocking model, whose soil parameters are evaluated on the basis of the continuum formulation method, and a finite element model, using the program SASSI with the flexible volume substructuring approach. The dependences of the soil parameters of both models on the amplitudes of the different dynamic excitations are investigated in detail. An original numerical simulation of microtremor is performed. Comparison with results of a previous study involving a rigid tower on a soft soil site in Chiba, Japan is offered.

Applications of Statistics and Probability to Seismic Disaster Mitigation Researches

There are many sources of uncertainties in the problems of earthquake engineering. These sources may be classified into three groups. They are (a) uncertainties In earthquake occurrences, (b).uncertainties In earthquake ground motions, and (c) uncertainties in structural response and seismic damage.