Problem Description
A one-story, one-bay in each direction, three-dimensional, fixed-base frame made of 2-inch steel pipe segments and 2.75-inch steel cubes is analyzed for the first 24 modal frequencies using eigenvectors. The frame is Problem No. 1 from the ASME 1972 Program Verification and Qualification Library (reference ASME 1972).
The material and section properties, and the mass at each node, shown in the figure below are consistent with those used in the above mentioned references. Because masses are specified in three directions at 14 nodes, this problem has a total of 3 * 14 = 42 dynamic degrees of freedom.
Results Comparison
| Mode | Output Parameter | OpenBrIM | SAP2000 | Independent | Percent Difference OpenBrIM - Independent | Percent Difference SAP2000 - Independent |
|---|---|---|---|---|---|---|
| 1 | Frequency | 111.2411 | 112 | 112 | 0.68% | 0% |
| 2 | Frequency | 115.8023 | 117 | 116 | 0.17% | 1% |
| 3 | Frequency | 137.1839 | 138 | 138 | 0.59% | 0% |
| 4 | Frequency | 215.8188 | 218 | 218 | 1% | 0% |
| 5 | Frequency | 404.1598 | 415 | 404 | 0.04% | 3% |
| 6 | Frequency | 422.5049 | 434 | 423 | 0.12% | 3% |
| 7 | Frequency | 451.4506 | 463 | 452 | 0.12% | 2% |
| 8 | Frequency | 548.8523 | 561 | 554 | 0.93% | 1% |
| 9 | Frequency | 733.3078 | 752 | 736 | 0.37% | 2% |
| 10 | Frequency | 758.2787 | 777 | 762 | 0.49% | 2% |
Tested Features
- Three-dimensional frame analysis
- Modal analysis using eigenvectors
- Joint mass assignments