Tham khảo tài liệu 'marine_structural_design episode 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 178 Part II Ultimate Strength Integrating AFb and AMb respectively the force Fb and the bending moment Mb acting at the bottom of a dent are obtained as Fb 2 AFbd0 Mb 2 AMbde where a represents a half dent angle and has a limiting value aL as mentioned in Chapter . After a is attained two other dents are introduced as illustrated in Figure c . For the specimen tested in this chapter aL zr 4 which coincides with the calculated results by . 1983 . Applying this model the stress distributions after local buckling may be represented as shown in Figure . In this figure the case with one dent is indicated as case A distribution and that with three dents is a case B distribution. For a case A stress distribution Eqs. and are replaced with P eo 3 3 4 577 Ụ t 6 where Z Fw Pị is the angle of the center of the i-th dent measured from the vertical centerline as shown in Figure . For a case B stress distribution Eqs. and are replaced with p l e0 3 fĩ hA -hy 5 i4 ự ụ i 6 9-63 Procedure of Numerical Analysis Until initial yielding is detected Eq. gives the relationship between axial compressive loads and lateral deflection. The mean compressive axial strain is evaluated by Eq. . After plastification has started the analysis is performed in an incremental manner using the plastic component of deflection shown in Figure . This deflection mode expressed by Eqs. thru gives a constant plastic curvature increment in the region I. If the actual plastic region length d in Figure a is taken as I it reduces to prescribe excess plastic curvature especially near the ends of the plastic region. To avoid this a bi-linear distribution of plastic curvature increments is assumed in the region ld as indicated in Figure b . Then the change of the plastic slope increment along the plastic region may be expressed as d6p lddKp 2 Chapter 9 Buckling and Local Buckling of Tubular Members .
