Verification › V.04 Dynamic analysis
V.04.2Space Frame with Joint Masses
All 12 frequencies match STAAD.Pro's 3 decimalsOpen in the app and solveNo sign-up needed: it runs in your browser.
Problem
Find the natural frequencies, mass participation and dynamic weight of a space frame whose masses are joint masses that differ by direction.
Reference
- STAAD.Pro V8i SS6, the same input file run by Sutranet (no published solution).
Model
- Two-storey, 2 × 1 bay space frame with unsymmetric prismatic columns and beams
- One bay X-braced with truss members
- Joint masses given as loads in the mass case, different in X, Y and Z; one sits on a support, which STAAD drops
Comparison
| Mode | STAAD.Pro | Sutranet | Difference |
|---|---|---|---|
| 1 | 1.524 | 1.524 | none |
| 2 | 1.572 | 1.572 | none |
| 3 | 2.064 | 2.064 | none |
| 4 | 2.563 | 2.563 | none |
| 5 | 4.166 | 4.166 | none |
| 6 | 4.259 | 4.259 | none |
| 7 | 4.611 | 4.611 | none |
| 8 | 5.040 | 5.040 | none |
| 9 | 6.715 | 6.715 | none |
| 10 | 15.536 | 15.536 | none |
| 11 | 30.269 | 30.269 | none |
| 12 | 30.332 | 30.332 | none |
| Direction | STAAD.Pro | Sutranet | Difference |
|---|---|---|---|
| X | 690.0 | 690.000 | none |
| Y | 690.0 | 690.000 | none |
| Z | 390.0 | 390.000 | none |
- Mass participation agrees within 0.005 percentage points in every mode. The same frame with self-weight as mass also matches.
Reproduce in Sutranet CAD
- Open the project in the app (no sign-up needed), or download the file and open it with 📂 Import Job JSON in the File group.
- Modal Analysis (member self-mass is off in this project, as in the STAAD mass case).
The app works in SI units; results in kip and inch are converted (1 kip = 4.448 kN, 1 kip-in = 0.1130 kN·m, 1 in = 25.4 mm).
Automated test: staad_modal.rs, run on every change.
Run your own models the same way
Create free accountFree account: build frames, trusses and towers, import STAAD .std files, and run IS 800 and AISC design checks in your browser.