２相ステンレスＰＣ鋼材の基礎的諸特性およびこれを用いたプレストレストコンクリート部材の曲げ載荷特性に関する研究

Abstract

The duplex stainless prestressing steel has been developed for durable prestressed concrete members. This steel is cold drawn and has microstructure with two phases composed of ferrite (α) phase and austenite (γ) phase.The duplex stainless steel is excellent in durability. But there are few studies about cold drawn duplex stainless steel compared with those for annealed duplex stainless steel. So we have made research on both the basic properties of the duplex stainless prestressing steel and flexural behaviors of prestressed concrete beams using this tendon.This paper presents the results of tensile test, fatigue test, stress relaxation test, corrosion test and pull-out test, and further flexural test of the prestressed concrete beams using the tendon. The outlines of these results are as follows.The properties of fatigue and stress relaxation of the duplex stainless prestressing steel were roughly equal to those ordinary high carbon prestressing steel, and had satisfactory resistance to stress corrosion, chloride corrosion and satisfactory bond strength to concrete. The prestressed concrete beams using this tendon showed similar flexural behaviors to the concrete beams using the ordinary high carbon prestressing steel tendon.The duplex stainless prestressing steel is small in the elongation at ultimate strength and excellent in durability. Therefore, the tendon is suitable for the external cable system in which the cable tension is not expected to increase so large as in the internal cable system and durability is required. However, the behaviors of the cable at the saddle must also be investigated.A defect of the duplex stainless prestressing steel compared with high carbon prestressing steel is that the tensile strength is low.