API PUBL 937-A:2005 pdf download

API PUBL 937-A:2005 pdf download.Study to Establish Relations for the Relative Strength of API 650 Cone Roof Roof-to-Shell and shell-to-Bottom Joints.
3.1.3 Roof-to-Shell Joint Failure Pressure
Using the SafeRoof program, the pressure for failure of the roof-to-shell joint was calculated to be 1.04 psi. The criterion for failure of the roof-to-shell is yielding at the roof-to-shell joint in compression. This yielding then results in local buckling and kinking of the angle which causes the roof attachment weld to fail and to initiate detachment of the roof. Since the roof-to-shell failure pressure is greater than the balanced uplift pressure of 0.295 psi, significant uplift occurs before the roof-to-shell fails.
Both the roof-to-shell and the shell-to-bottom joints are in compression, as shown in the details of Figure 3-8 and Figure 3-9. This is due to the “doming” that has occurred in the roof (where it has lulled from the railers) and the “bowling” of the tank bottom (which has resulted in a concave bottom). The defonnations of both the roof and bottom result in inward radial displacements at the roof-to-shell and shell-to-bottom joints and a corresponding compressive circumferential stress.
At the bottom, the radius at which uplift starts is98 inches (8.16 feet). so that the bottom has uplifted for a radial distance of 6.83 feet from the tank wall. The uplift displacement of the tank shell is 4.6 inches.
Equivalent stresses for the middle surface are plotted in Figure 3-10. These show that the top angle is at yielding (approximately 36.000 psi), while the stresses at the shell-to-bottom joint are large (approximately 26,000 psi), but not yet at yielding. At this load, the circumferential stresses in the bottom near the shell are in compression, Figure 3-1 1. The meridional stresses are in tension, with the largest (approximately 5,300 psi) values in the center of the bottom. However, in all cases, the meridional tension stresses in the bottom are much smaller than the circumferential stresses near the shell-to-bottom joint. Therefore, they are not expected to cause failure.