What this document is
Every example in this section was built in vfopro, analyzed, and compared automatically against an independent reference: a closed-form textbook solution, an independently-solved eigenvalue problem, or a real, published, physically-tested specimen. This is the same practice structural analysis vendors have long used to publish a verification manual, and it is how we check our own work, not just describe it.
The document has two parts. Verification (Linear, Modal and Nonlinear) checks that vfopro builds the correct mathematical model and solves it correctly, against answers that can be derived independently by hand. Validation checks that vfopro's nonlinear modeling reproduces the measured behavior of real, physically-tested structures.
How a result is classified
Every quantity is compared as a percentage difference, 100 × (vfopro / reference − 1), and classified using the same convention long used in structural-analysis software verification manuals:
| Exact | Matches to at least 6 significant figures — the difference is at the precision limit of the printed output. |
| Acceptable | Within 5% for a displacement or force quantity, 10% for an internal force or stress quantity, or 10% when the reference is a physical test (test data itself carries measurement and specimen-to-specimen scatter, so validation against experiment is held to a looser band than verification against a closed-form or reference-software solution). |
| Unacceptable | Outside those bands. Every Unacceptable result is discussed in its own example page, with the reason for the gap. |
An example's overall status is its single worst individual check — one Unacceptable row is enough to mark the whole example Unacceptable, even where the great majority of checks pass. Validation examples, which are compared against physical tests, carry no status tag; their pages report every comparison and discuss the differences.
Browse by category
| Verification — Linear | Elastic frame (beam-column) and truss members under determinate and indeterminate loading, checked against closed-form beam theory and the method of joints. This is the foundation every other example builds on: if the basic elastic elements aren't exactly right, nothing built on top of them can be trusted either. | 9 examples |
| Verification — Modal | Natural periods from eigenvalue (Modal) analysis, checked against closed-form and independently-solved benchmarks. | 2 examples |
| Verification — Nonlinear | The two building blocks every nonlinear and cyclic model in the Validation category depends on: that a hinge reproduces its own input backbone exactly, and that a cyclic loading protocol is expanded into the correct displacement history. | 2 examples |
| Validation | Full nonlinear models of real, published, cyclically-tested specimens — reinforced-concrete walls, coupling beams and columns, a buckling-restrained brace, and a steel moment connection — compared against each specimen's own measured response. | 5 examples |
Summary
18 examples. The 13 verification examples: 12 Exact, 1 Acceptable. The validation examples are compared against test data and reported as comparisons, without a status tag. Each ID links to its own page with the full model, reference and comparison detail.
Scope & limitations
This document is about what vfopro can already do well, and it is just as much about being clear on what it cannot do yet. The following are current, known limits on vfopro's analysis capability — not defects, but boundaries this document does not claim to cross:
| Geometric nonlinearity | Only small-displacement (linear) member behavior is currently available. P-Delta and large-displacement (corotational) effects are not yet modeled. |
| Response spectrum analysis | Not yet available. |
| Shell elements | Elastic only. Nonlinear shell behavior (for example, a wall modeled as a layered shell rather than a fiber wall hinge) is not yet available. |
| Wall fiber hinges | One reinforcement ratio and one concrete model apply across the whole wall cross-section. Separate boundary-versus-web reinforcement zones within a single hinge are not yet supported — see VAL1, where the specimen's own zoning is applied at the mesh level instead. |
| Frame fiber hinges | No explicit shear–flexure interaction, and no explicit bar-fracture or bar-buckling degradation. A section keeps carrying load past the point where a real member's reinforcement would buckle or fracture — see VAL4. |
| Units | Analyses run in US units (kip, in, s). |
Not yet covered
This is the first edition of this document. It does not yet include:
- Shell verification (plate bending, in-plane wall panels, curved shells against closed-form and standard benchmark solutions).
- Additional modal verification (plate frequencies; multi-story building and wall models cross-checked against SAP2000/ETABS).
- Cross-checks of the frame, truss and modal examples above against SAP2000/ETABS, in addition to the closed-form references already used.
- Dynamic time-history validation against shake-table test data.
- Loop-shape and cumulative-energy validation for the coupling beam (VAL2), and refinement of the wall (VAL1) and column (VAL4) small-displacement stiffness.
These are planned for future revisions of this document.
Last updated September 22, 2026 · applies to vfopro 20260922.0.0 or later