Experimental evaluation of the axial capacity of cracked tubular member
Bachelor thesis
Permanent lenke
https://hdl.handle.net/11250/2774295Utgivelsesdato
2021Metadata
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Sammendrag
This thesis experimentally investigated the compressive axial capacity of cracked tubularmembers. Then compared it to NORSOK N-004 (Standard Norge 2004) formulae. Further,the test results were compared with other analytical models, such as non-linear finite elementanalysis from a separate thesis (Vågen 2021) and basic column formulae e.g. Perry Robertsonand the Secant method.
In this study, 11 tubular columns were tested with a diameter of 70 mm, 2.9 mm thickness,and 1.5 m height, due to the testing facilities limitation. Different crack sizes were placedperpendicular to the loading direction with sizes corresponding to NORSOK N-004 reducedcapacity of 25, 50 and 75%. The material properties were obtained by stub column tests. Tofurther study the effect of cracks on tubular members, angled cracks with respect to theloading direction were introduced to the stub column.For the specimens with cracks perpendicular to the loading direction, The test results weresomewhat unexpected and showed an inconsiderable reduction in the axial capacity, as thecrack surfaces bear on each other. However, the angled cracks introduced to the stub columnsshowed a considerable capacity reduction. The reduction is assumed to result from the cracksurface slipping, discontinuity in the material, and torsion due to the angled crack in the stubcolumn.
The conclusion was that angled cracks have the most significant impact on the compressiveaxial capacity. On the other hand, cracks placed perpendicular to the loading direction had aninsignificant effect on the capacity. Hence, the NORSOK N-004 formulae provide inaccurateformulas for capacity determination for such cases. Among the analytical methods presentedin this thesis, Perry Robertson gave the most accurate capacity. This result was somewhatexpected as the method was best adapted to the actual column behavior in the tests. This thesis experimentally investigated the compressive axial capacity of cracked tubularmembers. Then compared it to NORSOK N-004 (Standard Norge 2004) formulae. Further,the test results were compared with other analytical models, such as non-linear finite elementanalysis from a separate thesis (Vågen 2021) and basic column formulae e.g. Perry Robertsonand the Secant method.
In this study, 11 tubular columns were tested with a diameter of 70 mm, 2.9 mm thickness,and 1.5 m height, due to the testing facilities limitation. Different crack sizes were placedperpendicular to the loading direction with sizes corresponding to NORSOK N-004 reducedcapacity of 25, 50 and 75%. The material properties were obtained by stub column tests. Tofurther study the effect of cracks on tubular members, angled cracks with respect to theloading direction were introduced to the stub column.For the specimens with cracks perpendicular to the loading direction, The test results weresomewhat unexpected and showed an inconsiderable reduction in the axial capacity, as thecrack surfaces bear on each other. However, the angled cracks introduced to the stub columnsshowed a considerable capacity reduction. The reduction is assumed to result from the cracksurface slipping, discontinuity in the material, and torsion due to the angled crack in the stubcolumn.
The conclusion was that angled cracks have the most significant impact on the compressiveaxial capacity. On the other hand, cracks placed perpendicular to the loading direction had aninsignificant effect on the capacity. Hence, the NORSOK N-004 formulae provide inaccurateformulas for capacity determination for such cases. Among the analytical methods presentedin this thesis, Perry Robertson gave the most accurate capacity. This result was somewhatexpected as the method was best adapted to the actual column behavior in the tests.