E08: ASME Frame Eigenvalues
- Gokhan Alkan (Unlicensed)
This frame is from ASME 1972 Program Verification and Qualification Library. It is a single story 3D frame with a single bay in each direction. The frame is made of 2-inch steel pipe segments welded to 2.75-inch steel cubes. The legs are welded to a heavy base plate to assure full restraint.
Determine the lowest 24 natural frequencies and mode shapes of the 3D structure considering the shear deformations.
The material properties of the pipes are:
The pipe section is constant throughout with 2.375 in. outer diameter and 0.154 in. wall thickness. The section properties for the pipes are:
The self weight of the structure is represented by mass elements at the joints. The steel cubes are modeled as mass elements at the corner joints of the frame.
The mass elements at the corner joints including the weight of 2.75 inch steel cubes are:
The mass elements at all other joints are specified as:
The natural frequencies computed by LARSA are in good agreement with the values obtained by ANSYS and EASE2 programs. LARSA and COSMOS results are identical. In ANSYS and EASE2 solutions, 24 eigenvalues are computed using the Guyan reduction method retaining only 24 mass degrees of freedom, whereas in LARSA and COSMOS, the eigenvalue problem has been solved using all degrees of freedom.
Tested Features
Reference
- Program Verification and Qualification Library, ASME Pressure Vessel and Piping Division, Committee on Computer Technology, 1972.
Sources
- ANSYS, Engineering Analysis System, Examples Manual, Swanson Analysis Systems, Inc., Elizabeth, PA, 1977.
- EASE2, Elastic Analysis for Structural Engineering, Example Problem Manual, Engineering Analysis Corporation,
- COSMOS, Finite Element Analysis Program
- LARSA 4D