実体波と表面波から構成される地震動を受ける 弾塑性構造物に対する極限外乱

摘要

超高層建物や原子力施設などの重要構造物は，可能な限り幅広い特性の大規模地震に対して構造的に安全であり，継腰使用が可能であることが望まれる。地震による構造物の損傷は入力特性や構造物特性に依存し，不確定要素が多く予測することは困難である。しかしながら，起こり得る地震動の中で構造物の応答が最大となる最も危険な地震動（極限外乱）に対して建物を適切に設計することで，建物の安全性を大幅に向上させることができると考えられる1-6)。%This paper investigates critical earthquake inputs for multi-degree-of-freedom (MDOF) inelastic structures considering the evolution of seismic waves in time and frequency. The ground acceleration is represented as a combination of seismic waves with different characteristics. Each seismic wave represents the energy of the ground motion in certain frequency band and time interval. The amplitudes and phase angles of these waves are determined to produce the highest deformation or damage in the structure subject to (0 explicit constraints on the energy and the peak ground acceleration and (ii) implicit partial constraints on the frequency content and the arrival, time of the seismic waves. The material nonlinearity is modeled using a bilinear inelastic law and the member fracture is also included. The study explores also the influence of the properties of the seismic waves on the energy demand of the structure. Numerical illustrations on modeling critical earthquake excitations for several structures are provided.