METAL MEMBER AND METAL PLATE MEMBER HAVING DIFFERENT WIDTH EXCELLENT IN FATIGUE CRACK DEVELOPMENT AND PROPAGATION SUPPRESSING CHARACTERISTICS, METHOD OF MANUFACTURING THESE METAL MEMBERS, AND METAL STRUCTURE HAVING THESE METAL MEMBERS

摘要

A metal member or a metal structure used for buildings, ships, bridges, construction machinery, and offshore structures and excellent in fatigue crack development and propagation suppressing property and method of manufacturing the metal member and the metal structure. The metal member or the metal structure is formed in such a shape that a plate-like metal rib with a length of (l), a height of (h), and a thickness of (t2) is projected from a metal main plate or a metal main tube with a thickness of (t1). The metal member or the metal structure is characterized by comprising a dent with a compressive strain of 0.5 to 25% in a plate thickness direction at a position apart a distance (s) of t2/4 to 4·t2 from a rib plate end part where the main plate or the main tube crosses the rib in a direction parallel with an outside maximum tensile stress, the size of the dent is such that the length (b) thereof from that position is t2/4 to 4·t2 in the direction parallel with the outside maximum tensile stress, and the length (L) thereof in a direction vertical to the outside maximum tensile stress with respect to that position is t2/2 to (5/8)W, and a compressive residual stress acts on the rib plate end part where the main plate or the main tube crosses the rib plate by the dent, where (W) is the width of the main plate or the outer peripheral length of the main tube.