Current app version: StructureTool2D v3.0.
StructureTool2D © is a structural analysis and learning application for beams, frames, and trusses. The web interface is organized into three workflow tabs: A: Structure Data / Geometry, B-C: Stiffness / Slope-Deflection, and D-E: Unit Load / Force Method. The program uses Excel-based input workbooks, performs structural analysis, and produces plots, tables, DOCX reports, and instructional method outputs.
Tab A is the starting point. Use it to create a structure in the Builder, open an Excel structure data file, download the template, access resources, and preview the current structure.
If no user workbook is selected, the app can use the default structure template. When a workbook is loaded, the app reads its structure type and units, updates the preview heading, and prepares the related analysis tabs.
After a structure preview is generated, a thumbnail of the geometry appears in the left column when Tab B-C or Tab D-E is active. The thumbnail is hidden in Tab A.
The Builder supports frame, beam, and truss models. It can create nodes, members, supports, member-end hinges, nodal loads, member loads, dimension lines, custom label positions, display colors, number or letter node labels, node visibility, grid/axes visibility, and image exports.
Builder display items such as dimensions, manual label positions, colors, node-label style, node-marker visibility, and grid/axes visibility are visual aids. They do not change the analysis data written to the standard Excel workbook.
Use Builder Instructions for the full Builder workflow, including import, export, units, supports, hinges, loads, dimensions, labels, colors, and pre-analysis checks.
The Builder supports the app unit settings used by the workbook. Keep one consistent unit system for the full model. Changing the unit setting after building a model changes the active unit setting for input. It does not automatically convert all existing numerical values, so review coordinates, loads, E, A, and I if units are changed after objects have been created.
Section B1 contains the settings used by stiffness analysis and plot generation.
| Control | Use |
|---|---|
| No. Elements/Member (NE) | Controls member discretization where needed. NE updates automatically from the Structure Type dropdown. Truss sets NE = 1. Beam and Frame set NE = 10. |
| Deflected Shape Mag. Factor | Initial value is 10. After analysis, the app updates this value so the maximum plotted deflection is about 12.5% of the structure reference length. The displayed value is rounded to 2 significant digits. |
| Scaling Factor M, N, V Plots | Controls the diagram scale for beam and frame M, N, and V plots. Default value is 0.5. |
| Structure Type | The app auto-selects Truss, Beam, or Frame from the workbook. You may change the dropdown manually if needed. Changing this dropdown also updates NE automatically. |
| Show Node Numbers | Checked by default. It controls node-number display in the plots where the option applies. |
| M on tension side | Available for beams and frames. It controls the displayed moment sign convention. |
| M, N, V checkboxes | For beams, M and V are available and N stays inactive. For frames, M, N, and V are available. For trusses, these checkboxes stay inactive. |
| Reset Analysis | Clears the current analysis state and restores the default workbook state. |
| Solution Report (NE = 1) | Creates a student-style stiffness solution report for beam, frame, or truss models using NE = 1. |
2) Plot Structure Geometry can be used before analysis. Buttons 4 to 8 remain inactive until 3) Analyze Structure is completed. After analysis, the available buttons depend on the detected or selected structure type.
| Structure type | Active after analysis | Inactive after analysis |
|---|---|---|
| Truss | 4) Display Analysis Results, 5) Display Deflected Shape, 6) Display Truss Axial Forces | 7) Plot M, N, V Diagrams, 8) Plot Geometry, Loads & Reactions |
| Beam | 4) Display Analysis Results, 5) Display Deflected Shape, 7) Plot M, V Diagrams, 8) Plot Geometry, Loads & Reactions | 6) Display Truss Axial Forces, N diagram checkbox |
| Frame | 4) Display Analysis Results, 5) Display Deflected Shape, 7) Plot M, N, V Diagrams, 8) Plot Geometry, Loads & Reactions | 6) Display Truss Axial Forces |
After analysis, the app computes a practical magnification factor for the deflected-shape plot. It uses the largest practical structure dimension, based on global span and maximum member length, as the reference length. The target displayed maximum deflection is about 12.5% of that reference length. The app writes the rounded value back into the Deflected Shape Mag. Factor field, and button 5 uses that value.
For beams, the app plots bending moment and shear diagrams. Axial-force plotting is inactive for beams. For frames, the app can plot bending moment, axial-force, and shear diagrams based on the selected M, N, and V checkboxes.
For beam and frame geometry, loads, and reactions plots, the app draws reactions and labels near the support direction. These plots are visualization aids and should be checked against the numerical reaction values in the analysis results.
In Section 5 of the truss stiffness solution report, the member axial force at the start node is computed by projecting the global start-node force components onto the member local x-axis:
Ni = Fx,start cos θ + Fy,start sin θ
The report uses this sign convention: if Ni < 0, the member is in tension. If Ni > 0, the member is in compression. Values within a small numerical tolerance are reported as zero force.
Section C provides a dedicated Slope-Deflection Method workflow for eligible beam and frame workbooks. It summarizes classification, active unknowns, sidesway condition, solved unknowns, maximum absolute end moment, and stiffness-check information when available.
The current SDM implementation is intended for continuous beams and rectangular frames, with a maximum of one degree of sidesway and inextensible members.
Section D computes a truss displacement or redundant support reaction using the Unit Load Method or the Force Method. Select the target node and direction, then run the enabled method. The app enables ULM for determinate trusses and FM for supported 1-degree support-indeterminate trusses.
Section E provides the same type of instructional workflow for beam and frame workbooks. Target directions may be x, y, or rz. Positive x is to the right, positive y is upward, and rz follows the beam/frame solver convention.
The app enables ULM for determinate beam/frame workbooks and FM for supported 1-degree support-indeterminate beam/frame workbooks.
Educational Purpose: StructureTool2D © is intended primarily as an educational and instructional tool. It is designed to help users study structural modeling assumptions, stiffness-based analysis, slope-deflection relationships, unit-load concepts, force-method concepts, load idealization, deformation patterns, internal-force development, and overall structural response.
Users are expected to exercise sound engineering judgment and independent verification when preparing input data, interpreting analysis results, and drawing conclusions from the software output. Results should always be checked for consistency and reasonableness.
This software is provided for educational use, demonstration, and preliminary study purposes only. No warranty or guarantee is given that the application is free from errors, omissions, numerical limitations, modeling assumptions, coding defects, or user-input effects. The author and distributors accept no liability for any loss, damage, claim, or consequence arising from the use of the software or from reliance on its results.
StructureTool2D © must not be used as the sole basis for final engineering design, professional certification, construction decisions, or safety-critical assessment without independent checking and verification by a qualified engineer.