約20年間暴露されたGFRP引抜成形箱形断面部材に対する残存曲げ性能の実験的評価

Abstract

GFRP引抜成形材は土木構造部材として広く用いられているが，長期暴露後のデータが少なく耐久性が不明確なことが，主要構造部材としての普及を妨げる一因となっている．本研究では，長期暴露後のGFRP引抜成形部材の残存性能を明らかにすることを目的に，約20年間屋外暴露されたGFRP引抜成形角パイプ及び同期間室内保管されていた同パイプを対象に，静的4点曲げ試験を行うことにより残存曲げ性能を明らかにした．また，長期暴露後においてもチモシェンコのはり理論により変形挙動を概ね評価可能であることを確認した．さらに，曲げ耐荷力を局部座屈応力の計算値や初等はり理論を用いて計算される破壊荷重と比較し，暴露後の供試体においては，載荷に伴う角部の破壊進行により回転拘束効果が低下し局部座屈耐荷力が小さくなる可能性を示した．

GFRP pultrusion-molded materials are widely used as civil engineering structural members, but they are not widely used as main structural members due to the lack of data after long-term exposure and unclear durability. In this study, static four-point bending tests were conducted to clarify the residual performance of GFRP pultrusion-molded members after long-term exposure. Specimen used in the tests were GFRP pultruded square pipes exposed outdoors for approximately 20 years and on GFRP pultruded square pipes stored indoors for the same period. As a result, authors revealed that the residual stiffness and bending load capacity of these members decreased after the exposure. It was also confirmed that the deformation behavior could be generally evaluated based on Timoshenko's beam theory even after long-term exposure. The obtained bending load capacities were compared with the calculated load capacities using the local buckling stress and elementary beam theory, and it was shown that the deterioration of the corners due to exposure may accelerate the progress of corner failure with loading and reduce the effect of rotational restraint, resulting in a smaller local buckling load capacity.