Design Method for RC Beams to Reduce Residual Deformation and Construction of Highly Reproducible Analytical Model for RC Frames

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04365
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 23010:Building structures and materials-related
• Research Institution: Kagoshima National College of Technology
• Principal Investigator: KAWASOE Atsuya 鹿児島工業高等専門学校, 都市環境デザイン工学科, 教授 (50710290)
• Co-Investigator(Kenkyū-buntansha): 安井 賢太郎 鹿児島工業高等専門学校, 都市環境デザイン工学科, 准教授 (70897701)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 残留変形 / 二次剛性 / MSモデル / 復元モーメント / 高強度鉄筋

Outline of Final Research Achievements

A design method for RC beams that reduces residual deformation after earthquakes by using high-strength rebars at the top of the beams and exerting secondary stiffness in the skeleton curve has been proposed for low- to mid-rise reinforced concrete buildings that are prone to beam yielding. Loading experiments were conducted on the improved beams, and it was confirmed that the test specimens using SD685 for the upper reinforcement were capable of simultaneously reducing both residual deformation and maximum shear force.
Analytical models of the improved beams and column bases were created using models with rotational springs and multi-springs, and the hysteretic characteristics were largely reproduced. Using the above analytical models of columns and beams, analytical models of an RC frames were created, and a response analysis was performed using seismic waves to clarify the effect of the improved beams in reducing residual deformation.

Free Research Field

建築構造

Academic Significance and Societal Importance of the Research Achievements

大地震により大変形しても，残留変形を無視できる程度に抑制するRC建物の可能性について示した。提案する建物は，梁の下端の普通鉄筋が早期に降伏した後，上端の高強度鉄筋による二次剛性の効果によって，層間変形角が1/100rad.程度では残留変形は生じず，1/50rad.に達しても残留変形を1/400rad.未満に抑制する。また，建物に想定外の変形が生じても層せん断力が大きく上昇しないように，梁の部材角が1/50rad.程度で降伏するように高強度鉄筋の降伏強度によって制御する。このようなRC建物は，地震による残留変形を抑制する様々な従来工法に比べて簡単かつ安価であり，施工費用の抑制に効果的である。