Evaluation of peeling risk and improving safety by ensuring unity on the interface between existing concrete and repair materials

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K04309
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22010:Civil engineering material, execution and construction management-related
• Research Institution: Tokyo Metropolitan University
• Principal Investigator: Uji Kimitaka 東京都立大学, 都市環境科学研究科, 教授 (70326015)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: コンクリート構造 / 補修・補強 / 施工

Outline of Final Research Achievements

The shear loading capacity in existing RC beams increases by attaching repair materials, for example, the carbon fiber reinforced plastic (CFRP) grids and the polymer cement mortar (PCM) to side areas of base concrete beams. In this study, the relation between shear bond strength and roughness, type of repair material, shape of bonding area, the shift of shear resisting area, were investigated.
Shear bond strength was directly proportional to the degree of surface roughness. From the experimental results and AE measurement results, it was clarified that the bearing areas of shear bond stress was limited at the bottom and upper part of specimen, which were near the loading point. The shear bond strength decreases as the area increases. Also, it was confirmed that the shear bond strength changes depending on the shape. Even if the total areas are same, the vertically long specimen show small value compared with horizontally long specimen.

Free Research Field

土木工学

Academic Significance and Societal Importance of the Research Achievements

本研究から、実務において考慮すべきせん断付着強度の考え方を、界面形状・面積や凹凸性状、断面修復材の種類・強度を要因として提示した。なお、せん断付着応力に対して界面の全面積が同時に抵抗するのではなく、面積のみに着目して補強設計を行うと、安全性に大きな問題を生じかねないことを示した。また、既設コンクリート構造物の補修・補強において、CFRP格子筋や金網を配置して断面修復材を施工することを想定した試験の結果から、付着面積の増加に伴いせん断付着強度が低下することが確認され、1格子内部の付着面積を考慮して、せん断付着強度を設定する必要があることを明らかにした。