The Roof Evaluation/Design report details the results of the design or analysis of supported cone roofs, and the results of the computations made according to the rules of API-650 Appendix F. The roof report begins with the required thickness and actual weight of the roof plates, and the design roof load.
If a supported cone roof was designed or analyzed, the resulting structural member sizes and loads are reported next. This information begins with the number of girder rings, the radius to each girder ring, and the number and length of the girders in each ring. This report is shown below.
Also shown above are the rafter details. This information includes the number of rafters in each rafter ring, the spacing on the outer girders, the number of rafters resting on the outer girders, the spacing on the inner girders, the number of rafters resting on the inner girders, and the rafter length. Note that at the center of the tank, and at the shell, the number of rafters per girder is reported as zero.
The next section of the (supported cone roof) report details the rafter and girder sizing parameters. This information includes the unit load on the member, the selected cross section, the required section modulus, and the actual section modulus. This information is provided for each rafter and girder ring, and is shown below.
The next section of the (supported cone roof) report details the column sizing parameters. This information begins with the column load, height, allowable compressive stress, and required radius of gyration. This is followed by the selected cross section, the actual compressive stress, and the actual radii of gyration. This information is shown below.
Following the column sizing details is the summary of the checks made according to Section 5.10.3. These checks determine the acceptability of the structural elements based on allowable stresses and unbraced lengths.
Following these checks is a weight summary of the supported cone roof components.
Following the roof design/analysis report are the results of the Appendix F computations. This information begins with the uplift force due to internal pressure and the resisting force due to tank weight.
This information is followed by the maximum design pressure limited by uplift, the maximum pressure at the roof/shell junction, and the compression ring failure pressure. All pressures are reported in the user’s units for pressure and in “inches of water”, an API unit.
The last section of the roof report shows the required area of the roof/shell junction as per Section F.5, and either 5.10.5 or 5.10.6.