1. Software Overview & Engineering Engine Architecture
SpaceGass is an industry-leading 3D structural frame analysis, finite element, and steel/concrete design software package widely deployed across Australia, New Zealand, the UK, and international engineering consultancies. Recognized for its high-speed numerical stiffness matrix solver and unmatched graphical interface for 3D space frames, SpaceGass is the industry standard for industrial portal frame buildings, complex space trusses, pipe racks, bridge superstructures, and high-rise structural steelwork.
In professional structural engineering practice, SpaceGass provides complete integration between 3D frame static/dynamic FEA, non-linear geometric P-Delta sway analysis, linear eigenvalue buckling mode extraction, and structural steel verification according to AS4100:2020 (Australian Steel Standard), NZS 3404:1997 (New Zealand Steel Standard), and Eurocode 3 (EN 1993-1-1).
Structural Performance: SpaceGass solves multi-degree-of-freedom space frames with member-level compression buckling verification ($\phi N_{cx}, \phi N_{cy}$) and lateral-torsional buckling moment capacity ($\phi M_b$) in real-time with automated section optimization loops.
2. 3D Space Frame Solver & FEA Matrix Formulations
SpaceGass models 3D space frame structures using 6-degree-of-freedom per node Timoshenko frame elements that account for axial, torsional, bi-axial bending, and shear deformations:
| Solver Module | Numerical Method / Matrix Formulation | Engineering Application |
|---|---|---|
| Linear Static Solver | Direct sparse Matrix Decomposition $[K] \{u\} = \{F\}$ resolving 6 DOFs per node ($u_x, u_y, u_z, \theta_x, \theta_y, \theta_z$). | Primary gravity Dead, Live, and Wind force distribution. |
| Non-Linear P-Delta Engine | Iterative Newton-Raphson update of geometric stiffness $[K_g(P)]$ under axial force vector $P$. | Sway displacement amplification in slender portal frames and tall building columns. |
| Eigenvalue Buckling | Generalized eigenvalue solution: $( [K] - \lambda_i [K_g] ) \{\psi_i\} = 0$. | Critical global frame buckling multiplier $\lambda_{cr}$ and mode shape extraction. |
| Dynamic Frequency | Subspace iteration mode extraction $[K] \{\phi_i\} = \omega_i^2 [M] \{\phi_i\}$. | Natural frequency (Hz) check for floor vibration and dynamic wind response. |
3. AS4100:2020 Steel Member Capacity Verification Equations
SpaceGass automates AS4100 structural steel design checks across all load combinations. The fundamental member capacity equations evaluated by the solver include:
A. Section Flexural Capacity ($M_s$) & Member Buckling ($M_b$)
For I-sections (UB, UC, PFC) bending about the major axis:
Section Capacity: M_s = f_y * Z_e
// Where Z_e is the effective section modulus accounting for plate compactness (Class 1-3).
Member Buckling Capacity: M_b = α_m * α_s * M_s ≤ M_s
// α_m is the moment distribution modifier along segment length L_e.
// α_s is the slenderness reduction factor: α_s = 0.6 * [ sqrt( (M_s / M_oa)^2 + 3 ) - (M_s / M_oa) ]
B. Combined Axial Compression & Bi-Axial Bending Interaction
Members subjected to simultaneous axial compression load $N_{Ed}$ and bending moments $M_{x,Ed}, M_{y,Ed}$ must satisfy the AS4100 Section and Member interaction checks:
In-Plane Section Utility: ( N_Ed / (ϕ N_s) ) + ( M_xEd / (ϕ M_sx) ) + ( M_yEd / (ϕ M_sy) ) ≤ 1.0
Out-of-Plane Member Buckling Utility:
( N_Ed / (ϕ N_c) )^γ + [ ( M_xEd / (ϕ M_bx) ) * ( 1 / (1 - N_Ed / N_omx) ) ]^0.6 + [ ( M_yEd / (ϕ M_sy) ) ]^0.6 ≤ 1.0
4. Industrial Portal Frame Design & Restraint Configuration
Portal frames require precise definition of flange restraint types to avoid over-conservative effective length defaults in automated design runs:
[Geometry Setup] → [Restraint Codes (FF, FL, FU)] → [P-Delta Run] → [Eigen Buckling] → [AS4100 Auto-Select]
- 1
Fly-Bracing & Restraint Setup
Define top/bottom flange lateral and torsional restraint codes at purlin/girt locations (e.g.
F= Fully Restrained,L= Laterally Restrained,U= Unrestrained) to reflect actual structural steel detailing. - 2
Haunch & Tapered Section Modeling
Model rafter knee haunches and apex connections using non-prismatic tapered frame elements with dynamic web depth updates along member axis $x$.
- 3
Non-Linear Second-Order Sway Check
Execute non-linear P-Delta analysis under governing load combination ($1.2G + 1.5Q + 1.0W$) to verify roof apex sway limits ($\delta_{sway} \le H / 150$).
- 4
Section Auto-Optimization
Run the SpaceGass steel section optimizer to evaluate universal beams (UB), channels (PFC), and hollow sections (RHS/SHS), outputting the minimum weight profile with governing utility ratio $\le 0.95$.
5. SpaceGass Batch Input & API Interface
SpaceGass supports headless batch file input (`.txt` / `.xml` script files) for automated structural parametric generation. Below is a structured SpaceGass text script defining nodes, materials, members, and running an AS4100 design check:
! SpaceGass Batch Input Script: 3D Steel Truss Node & Member Definition
NODE_DATA
1, 0.000, 0.000, 0.000, FIX=FIXED
2, 3000.0, 0.000, 0.000, FIX=FREE
3, 6000.0, 0.000, 0.000, FIX=PINNED
4, 1500.0, 2500.0, 0.000, FIX=FREE
5, 4500.0, 2500.0, 0.000, FIX=FREE
END_NODE_DATA
MATERIAL_DATA
1, NAME="Grade 300 Steel", E=200000.0, G=80000.0, DENSITY=7.85e-9, FY=300.0
END_MATERIAL_DATA
SECTION_DATA
1, NAME="460UB74.6", TYPE=UB, B=190.0, D=457.0, TF=14.5, TW=9.1, AREA=9500.0, IX=297e6, IY=16.7e6
2, NAME="150x150x6.0SHS", TYPE=SHS, B=150.0, D=150.0, T=6.0, AREA=3410.0, IX=12.1e6, IY=12.1e6
END_SECTION_DATA
MEMBER_DATA
1, N1=1, N2=4, SEC=1, MAT=1, RELEASE=RIGID
2, N1=4, N2=5, SEC=1, MAT=1, RELEASE=RIGID
3, N1=5, N2=3, SEC=1, MAT=1, RELEASE=RIGID
4, N1=1, N2=2, SEC=2, MAT=1, RELEASE=PIN_PIN
END_MEMBER_DATA
DESIGN_CODE
CODE=AS4100-2020, METHOD=LIMIT_STATE, PHI_F=0.90, PHI_C=0.90, MAX_UTIL=0.95
END_DESIGN_CODE
6. Technical Specifications & Features Matrix
| Feature Domain | Technical Capability / Standard |
|---|---|
| Structural Solvers | Linear Static, Non-Linear P-Delta, Linear Eigenvalue Buckling, Dynamic Natural Frequency, Transient Time-History |
| Design Code Engines | AS4100:2020 (Steel), AS3600:2018 (Concrete), NZS 3404:1997, Eurocode 3 (EN 1993-1-1), BS 5950, AISC 360-16 |
| Member Libraries | BHP/OneSteel Standard Sections, Lysaght Cold-Formed Purlins, European HD/HEB/IPE, US Wide Flange (W-shapes) |
| BIM & CAD Interfaces | Revit Structure 2D/3D Link, IFC4 Export, AutoCAD DXF Structural Wireframe, MS Excel CSV Batch Interface |