Worst input direction of critical earthquake ground motion for irregular-shaped building structure and its plastic collapse mechanism

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K14871
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 23010:Building structures and materials-related
• Research Institution: Kyoto Institute of Technology
• Principal Investigator: Kojima Kotaro 京都工芸繊維大学, デザイン・建築学系, 助教 (10822786)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: ダブルインパルス / 断層近傍地震動 / 極限地震応答 / 不整形立体骨組 / 最悪地震動入力方向 / 平面骨組 / 部材断面最適化 / 中間層免震建物

Outline of Final Research Achievements

An evaluation method of the worst input direction of the critical double impulse for elastic-plastic irregular-shaped building structures was proposed. The worst input direction of the critical double impulse is defined as the direction which maximizes the input energy into the building structure. The relation between the ground velocity amplitude and the worst input direction can be evaluated efficiently using this proposed method.
The critical pulse-like ground motion can be estimated easily by using the double impulse input. Taking advantage of this characteristic of the double impulse, the optimization problem is proposed to obtain the optimal member cross sections of steel building structures under the critical double impulse. Furthermore, the minimum ground velocity level of pulse-like ground motions, which can damage the isolation bearing and damper in the mid-story seismic isolation building, is evaluated.

Free Research Field

建築構造・材料

Academic Significance and Societal Importance of the Research Achievements

弾塑性構造物の極限応答や弾塑性等価周期の評価には、非線形時刻歴応答解析を用いて地震動の周期と振幅に対する繰り返し計算が必要である。また、不整形立体骨組や偏心建物では、地震動の入力方向も地震応答に影響する。しかし、地震動の振幅と振動数および入力方向を考慮すると極限的地震動の評価における計算負荷は膨大になる。
本研究課題では、パルス性地震動の近似としてダブルインパルスを導入している。ダブルインパルスを用いることで、地動速度振幅毎の最も危険なパルス性地震動（極限的ダブルインパルス）と弾塑性立体骨組への入力エネルギーを最大化する最悪方向を効率的に評価することが可能になる。