M-φ CHARACTERISTICS OF HIGH-STRENGTH STEEL PIPE PILES CONSIDERING LOCAL BUCKLING

Abstract

 In seismic performance verifications of steel pipe pile structures at port facilities, the evaluation of whether or not the calculation of the bending moment reaches full plastic moment is mainly performed by using the bilinear elasto-plastic model of M-φ characteristics. Since local buckling occurs in steel pipe piles with a large diameter-to-thickness ratio, which are used frequently due to economical design, the bending moment declines without reaching full plastic moment. On the other hand, the bending moment of steel pipe piles with a small diameter to thickness ratio slowly increase even after yielding, this effect cannot be taken into consideration in the above. Therefore, we have tried to clarify strength and deformation characteristics of steel pipe piles by three dimensional FEM analysis using shell elements, and we have proposed a verification method using ultimate curvature instead of full plastic moment. We have also confirmed that high strength steel pipe piles (570N/mm² tensile strength class) can cope with the same as conventional steel pipe piles by introducing a correction coefficient of yield stress.