2023-10-19 ピッツバーグ大学
◆部分的にデボンドされたストランドの使用は、プレストレス・コンクリート部材の潜在的な亀裂を減少させ、ガーダーの耐久性を高め、有用寿命を延ばすシンプルな技術です。研究では、部分的にデボンドされたストランドを使用することにより、ガーダーの局所応力が低減することが示されました。この結果は、AASHTOによって国立橋デザイン仕様に採用されました。
＜関連情報＞
- https://news.engineering.pitt.edu/cracking-down-on-cracked-concrete/
- https://www.pci.org/PCI/Publications/PCI_Journal/Issues/2023/March-April/Experimental-background-behind-new-AASHTO-LRFD-specifications-for-partially-debonded-strands.aspx
部分的に剥離したストランドの新しいAASHTO LRFD仕様の背景にある実験的背景 Experimental background behind new AASHTO LRFD specifications for partially debonded strands
Mathew W. Bolduc, Bahram M. Shahrooz, Kent A. Harries, Richard A. Miller, Henry G. Russell, and William A. Potter
Precast/Prestressed Concrete Institute Journal Published: March – April 2023
DOI:https://doi.org/10.15554/pcij68.2-01
Abstract
To develop a unified approach for the design of partially debonded strands in prestressed concrete highway bridge girders, a coordinated analytical and experimental investigation was conducted. This investigation examined amounts of partial debonding, distribution of partially debonded strands within the cross section, debonded lengths, locations and staggering of termination of debonded strands, confinement of debonded regions and their termination points, and the impact of adding nonprestressed reinforcement in the region of partial debonding. The results from testing full-scale I- and U-shaped girders indicate that partially debonding strands does not result in deleterious performance if adequate reinforcement is provided to resist the longitudinal tension due to bending and shear. Crack patterns and angles were not noticeably affected by the amount of debonding. Regardless of the debonding ratio, the maximum measured crack widths at the capacities predicted by the eighth edition of the American Association of State Highway and Transportation Officials’ AASHTO LRFD Bridge Design Specifications remained small. The requirements for debonded strands were revised significantly in the ninth edition of the AASTHO LRFD specifications based on the presented research.
