Seismic design by the response spectrum method: A new interpretation of elliptical response envelopes and a novel equivalent static method based on probable linear combinations of modes

摘要: Abstract At the design calculation phase, seismic analysis of a nuclear building is usually based on assumption structural linearity. Moreover, codes impose to consider three-component ground motions. In this context, response spectrum method likely most used approach. Different variants exist, main differences among them being related way superposing contributions three motion components and treatment simultaneity physically distinct responses. A set n r  ≥ 2 simultaneous values responses can be called vector . The basic provide peak value each response, allowing definition parallelepiped envelope for vectors: conservative since peaks responses, in general, do not occur simultaneously. Conversely, so-called elliptical envelopes , which are hyper-ellipsoids dimension correctly take into account simultaneity. first part paper, new interpretation presented, notion probable linear combinations modes practical use straightforward when  > 3, like e.g. case shell finite elements with membrane forces moments. standard procedure consists approximating by an enveloping polyhedron, whose vertices define vectors. refined closer surface envelope, proposed second paper. Another commonly approach equivalent static where action represented force field applied structure. difficulty application taking all contribution modes. novel loads described third article, pseudo-inertia last both load representative reinforced concrete building. results compared those obtained several classical method.