Strength Of Tubular Members Research Articles

Strength of Tubular Members Containing Holes

Abstract A small-scale, compressive-load test program was conducted at Chevron to determine the strength of tubular members with 1 to 3 holes. The parameters evaluated include the hole size, hole shape, hole location, and number of holes. Results from these tests provide a basis for platform ultimate strength calculations that are needed in making decisions on platform repairs. More than 50 specimens were tested in air under displacment control. Test specimen lengths were limited by the test apparatus to 45 in. (1,143 mm). Tubulars used in the test had an outside diameter of 3.5 in. (89 mm), which gave member slenderness ratios of about 40. The tests were needed because of the lack of relevant compression tests on members with holes. Based on test results, there appears to be a limiting value of hole size below which the compression-load capacity of the member is practically not affected by the existence of the hole. For example, a hole that is 10 percent of the member diameter does not significantly reduce member strength. This means remedial treatment is not necessary for many small holes, when ultimate strength is the controlling consideration. Nonlinear finite element shell analyses using both ADINA and FACTS computer programs and a simplified analysis using DENTA-II PC program were performed and results compared with data. We found that nonlinear finite element programs provide good predictions of capacities of members with holes, and that a simplified DENTA-II program provides adequate and efficient predictions.

Impact of code differences for tubular members

Abstract This paper discusses the impact on the design strength of tubular members caused by differences in specifications from various regions of the world. The specifications that are considered are the latest limit states design codes from five regions. Both circular and rectangular hollow sections manufactured by either hot-form or cold-form methods are considered. The first comparison deals with the column buckling strength. Codes differ not only in the design equations, but also in whether a distinction is made between hot- and cold-formed tubes. The design strengths resulting from these differences can be over 20%. The comparisons continue with the consideration of local buckling in thin-walled members in both axial compression and in bending. Not only do the equations for the local buckling strength differ, but the codes vary on whether an interaction with overall column buckling is considered. The conclusion of the paper is that the same tube, particularly thin circular sections, used in various part of the world may have a significantly different design strength. Some possible reasons for these differences are stated.