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No abstract available

[en] The Seismic Experience Database makes use of the empirical data gained from the actual performance of equipment in earthquakes throughout the world. The approach is really only the traditional scientific method, with the important proviso that there is no control over the ''experiment'' - the natural earthquake. The lack of control and hence the consequent objectivity of the data, mean that the experience data approach enjoys the credibility of realism that is unparalleled by computational or shaker table methods, resulting in a reduction in design pessimisms and hence project costs. The Database was developed as a result of a US Nuclear Regulatory Commission requirement for the operators of nuclear plant, mainly pressurized reactors to demonstrate the ability of critical systems and components in existing nuclear reactors and to withstand seismic events. The specific objectives of this approach were: to determine the most common causes of seismic damage or operational difficulties in facilities that contain structures, systems, equipment and components similar to those in nuclear facilities; to determine the threshold of seismic motion for various types of documented earthquake damage; to determine the performance of structures, systems, equipment and components regardless of the maximum levels of seismic motion; to determine minimum standards in equipment construction and installation to ensure the ability to withstand anticipated seismic loads; and to provide a much less costly qualification procedure. (author)

[en] This paper investigates quasi-static behavior of lead cave walls radiation shields made by stacking lead bricks. The bricks have high stiffness, whereas the joints are weak and incapable of supporting tension. Global behavior of this kind of wall is strongly influenced by size friction coefficient of the brick elements. The general finite element code ANSYS was used for the analysis of the lead caves. A series of 2-D models that spanned the range of height-to-width aspect ratios of the cave wall were constructed. Two types of contact elements were incorporated in the model. The point-to-point contact element was used to represent contact in the horizontal direction. This element permits either compression in the direction normal to the surfaces or opening of a gap. The point-to-surface contact element was chosen to represent contact in the vertical direction. This element allows sliding in addition to the compression or gap formation normal to the surface. A series of static analyses were performed for each model. A l-g. vertical acceleration representing gravity was applied. The lateral acceleration was increased until the solution would not converge. This acceleration is defined as the critical lateral acceleration. This was achieved with a set of load steps with increasing lateral load. The critical acceleration was found to depend on the wall aspect ratio. For a wall with an aspect ratio up to three, the maximum acceleration is above the required 0.1 g. The wall failure mechanisms were also identified based on the numerical results. The two failure modes are the rotation and loss of interlocking among the blocks or silding of upper layers of the wall

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[en] The study shows that the seismic response of two separated pics system is badly estimated by Rosenblueth's formula. Errors may reach 20% in the worst cases (little damping, one of the oscillators in a transitory phase, level ratio of the oscillators is nearly equal to 1). The averaged maximum is under-estimated in this case. To take these effects into account, we purpose a modified formula using the H function depending on the different parameters of the problem. This function is tabulated by numerical simulations. This tabulation is nearly complete except the cases of different dampings and both oscillators in the transitory phase. The proposed formula applies well to multi-degree of freedom systems even when their frequencies are close. The maximum is lightly overestimated. (orig./HP)

[en] The original article has been thus corrected with the corrected references and thus updated.

[en] A few basic notions which can be used for the seismological design are presented. All the study work and practical steps taken to protect the nuclear plants against possible earthquakes are described: main principles, design methods, tests, paraseismic steps

[en] The important basic facilities of public fields such as electric power, communication and gas, have been damaged due to the large earthquakes recently throughout the world. Especially, most of the electric panels which are essential to the operation of the basic facilities, are installed without anchorage on the access floor and then are very weak against the earthquake. Therefore, there is a high possibility that an electric panel may lose its function due to overturning and sliding during the earthquake. In order to prevent the damage of an electric panel on the access floor from the earthquake, seismic reinforcing system is developed and its seismic capacity is verified through the shaking table test in this study