LittleDef is optimized for high-performance structural analysis across multiple platforms:
SGI IRIX: Native desktop integration including .ftr files for icons and drag-and-drop support.
Linux & BSD: Full compatibility with Tcl/Tk 8.0 through 8.6.
Windows: Runs via the standard wish interpreter.
Performance: Uses a sparse stiffness assembly to minimize memory footprint. The fem_solver.so C accelerator provides a significant speedup for large-scale models.
2. Analysis Procedures
2.1 Linear Static Analysis
Calculates nodal displacements and internal forces (N, V, M) based on the Direct Stiffness Method. Results are visualized directly on the canvas; use the results toolbar to toggle different force components.
2.2 Second-Order & Stability
P-Delta Analysis accounts for the interaction between axial forces and lateral displacements, critical for slender frames. Stability Analysis computes the critical buckling factor (λcr) and identifies the primary buckling modes.
2.3 Modal & Seismic Analysis
The Modal Analysis module determines the natural frequencies and mode shapes of the structure. The Seismic Analysis uses these results in conjunction with a response spectrum to estimate earthquake loads according to EN 1998.
3. Eurocode Design Verification
LittleDef includes integrated verification modules that evaluate members based on Eurocode standards:
EN 1990 (EC0): Automated generation of ULS and SLS load combinations based on load case categories, including Second Generation (prEN 1990:2020) Equation 8.12 and consequence class scaling.
EN 1992 (EC2): Reinforced concrete design including N-M interaction diagrams, shear verification, and crack width control. Fully supports the **Second Generation** (EN 1992-1-1:2023) preview updates (CSCT-based shear capacity $V_{Rdc}$ without shear reinforcement, punching shear checking at $0.5d$, 2nd Gen crack width spacing factors, and dynamic column slenderness limit criteria).
EN 1993 (EC3): Steel design featuring automatic section classification (Class 1-4) and stability checks (Buckling, Lateral-Torsional Buckling). Fully supports the **Second Generation** (EN 1993-1-1:2022) preview (high-strength steels up to S700, moment distribution factor $f_M$, and Class 3 elasto-plastic classifications).
EN 1994 (EC4): Composite steel-concrete beam design verifications (ULS), checking plastic bending resistance, shear stud connections, and reinforcement ratio.
EN 1995 (EC5): Timber design considering load duration and moisture effects (kmod), including Second Generation (EN 1995-1-1:2025) materials.
EN 1996 (EC6): Masonry verification for vertical and shear resistance, including Second Generation (EN 1996-1-1:2024) compressive strength.
EN 1997 (EC7): Geotechnical pad footing checks, including soil-bearing resistance and sliding checks per Design Approaches (DA1_C1, DA1_C2, DA2, DA3), and Schmertmann's settlement estimation.
4. Productivity Tools
4.1 Load Case & Combination Manager
Organize loads into logical cases (Permanent, Variable, Snow, Wind). Create Result Envelopes to find the absolute maximum/minimum forces across all scenarios, ensuring a safe and conservative design.
4.2 Member Groups
Group individual elements into continuous Design Members. This is essential for accurate stability checks, as it allows the software to calculate the total system length rather than just the length of a single segment.
4.3 Model Healer
A suite of tools to maintain model integrity:
Merge Nodes: Consolidate nodes within a tolerance (e.g., 1mm).
Split Elements: Insert nodes at element intersections automatically.
Clean Geometry: Delete unconnected nodes and redundant elements.
4.4 Incremental Plasticity Analysis (Plastic Hinge Solver)
Predict ultimate collapse load multipliers and locate yielding zones. The event-to-event solver dynamically inserts physical hinges as components yield and reports the progressive collapse path in the status bar and console. Results are plotted on the canvas under the Plasticity status mode.
5. Keyboard Shortcuts
Key
Action
N
Add Node Mode
E
Add Element Mode
U
Add Support Mode
S
Selection Mode (Box/Pick)
Esc
Reset to Ready Mode / Clear Selection
Del
Delete Selected Items
Ctrl+F
Fit View to Window
Ctrl+L
Set active load case/combinations selector
F1
Open this User Guide
6. Command Line Interface (CLI)
For automated workflows, LittleDef can be run without the GUI: