3.1 System Overview
Section 3 defines the primary structural skeleton of each floor module. It consists of a radial truss network integrated with dual circumferential ring beams, forming a continuous diaphragm at every 4.5‑meter level.
Primary Structural Role
- Forms a continuous diaphragm at each floor
- Transfers gravity loads to both core and perimeter
- Transfers lateral loads to the core (primary) and outer frame (secondary)
- Provides torsional stiffness for the helical geometry
- Creates redundant load paths and structural continuity across the full tower height
3.2 Global Geometry
| Floor-to-floor height | 4,500 mm |
|---|---|
| Outer diameter (base level) | Ø220,000 mm |
| Inner ring diameter | Ø160,000 mm |
| Central core diameter | Ø24,000 mm |
| Radial truss length | 98,000 mm |
| Radial spacing | 15° increments |
| Number of radial trusses | 24 per floor |
| Number of floor rings | 2 (inner + outer) |
| Module floor area | ≈ 38,013 m² |
3.3 Structural Configuration
Radial System
- 24 radial trusses
- Spaced at 15° intervals
- Connect the central core → inner ring → outer ring
Ring Beam System
- Outer Floor Ring Beam
- Inner Floor Ring Beam
Together, these act as circumferential compression/tension rings, stabilizing radial trusses and resisting torsion and lateral deformation.
Vertical Profile
- Radial trusses slope 4.5° downward (outer → inner)
- Enables load convergence toward core
- Improves drainage and service routing
3.4 Component Breakdown
1. Outer Floor Ring Beam
- Diameter: Ø914 mm
- Wall thickness: 40 mm
- Material: Duplex Stainless Steel (EN 1.4462)
- Function: Outer compression ring transferring loads to perimeter mega‑frame
2. Inner Floor Ring Beam
- Diameter: Ø711 mm
- Wall thickness: 35 mm
- Material: Duplex Stainless Steel
- Function: Intermediate load collector distributing loads between trusses
3. Secondary Floor Beams
- Section: 300 × 600 mm rectangular
- Wall thickness: 25 mm
- Material: 316L Stainless Steel
- Quantity: 48 typical
- Function: Supports deck system and transfers load to radial trusses
4. Radial Truss Chords (Top & Bottom)
- Section: Ø508 mm CHS
- Thickness: 25 mm
- Material: Duplex Stainless Steel
- Length: 98,000 mm
- Function: Primary axial load‑carrying members
5. Radial Truss Diagonals (Web Members)
- Section: Ø323.9 mm CHS
- Thickness: 20 mm
- Material: Duplex Stainless Steel
- Function: Triangulated system carrying shear forces and preventing buckling
6. Diaphragm Bracing
- Section: Ø219.1 mm CHS
- Thickness: 12.5 mm
- Material: 316L Stainless Steel
- Function: Provides diaphragm stiffness and connects adjacent trusses
7. Connection Node Assemblies
- Custom cast stainless steel nodes
- Thickness ≥ 60 mm
- Multi‑directional tube sockets
- Hybrid weld + bolt connections
8. Floor Deck
- Composite steel deck
- Thickness: 60 mm composite system
- Material: 316L Stainless Steel
9. Finished Floor
- Architectural layer (non‑structural)
3.5 Connection Node Engineering
Node Geometry
- Multi‑axis tubular connection hub
- Supports radial trusses, ring beams, and secondary members
Typical Node Dimensions
| Node width | 900 mm |
|---|---|
| Vertical dimension | 914 mm |
| Minimum thickness | 60 mm |
Connection Method
- Full penetration welds (primary)
- High‑strength stainless steel bolts (backup)
- All welds ground and passivated
3.6 Member Schedule
| Outer ring beam | Ø914 mm × 40 mm — Duplex SS — 1 |
|---|---|
| Inner ring beam | Ø711 mm × 35 mm — Duplex SS — 1 |
| Secondary beams | 300×600 mm × 25 mm — 316L SS — 48 |
| Radial truss chords | Ø508 mm × 25 mm — Duplex SS — 48 |
| Radial diagonals | Ø323.9 mm × 20 mm — Duplex SS — Multiple |
| Diaphragm bracing | Ø219.1 mm × 12.5 mm — 316L SS — Between trusses |
3.7 Material Properties
| Yield strength | 450 MPa |
|---|---|
| Tensile strength | 650 MPa |
| Elastic modulus | 200 GPa |
| Shear modulus | 77 GPa |
| Density | 7,850 kg/m³ |
| Thermal expansion | 13.5 × 10⁻⁶ /°C |
| Fire resistance | ≥ 2.5 hours |
| Corrosion resistance | Excellent (<2.5% loss) |
3.8 Design Loads
Gravity Loads
| Dead load | 5.0 kN/m² |
|---|---|
| Live load (office) | 3.0 kN/m² |
| Total service load | 8.0 kN/m² |
Lateral Loads
- Wind pressure (per Section 12)
- Seismic base shear (per Section 12)
- Diaphragm behavior: rigid
Ultimate Load Combinations
- 1.2D + 1.6L
- 1.2D + 1.0W
- 1.0D + 1.0E
3.9 Structural Behavior & Engineering Logic
Load Path
- Floor loads → deck
- Deck → secondary beams
- Secondary beams → radial trusses
- Radial trusses → inner ring, outer ring, central core
Ring Beam Function
- Act as continuous tension/compression hoops
- Prevent radial spreading and local instability
- Enhance global stiffness and torsional resistance
Truss Behavior
- Triangulated system for efficient axial force transfer
- Web diagonals resist shear and buckling
Torsional Stability
- Dual‑ring system + radial grid creates closed structural loop
- Essential for helical rotation and wind‑induced torsion
Redundancy
- Multiple load paths: core + inner ring + outer ring
- Failure of one element redistributes load through network
3.10 Fabrication & Construction Notes
- All tubes: seamless stainless steel
- Welds: full penetration groove welds
- All welds ground smooth and passivated
- Connections fully welded and/or bolted
- Fabrication tolerance: ±5 mm
- Installation tolerance: ±10 mm
3.11 System Summary
The Radial Floor Truss & Ring Beam System forms the primary structural backbone of each floor. It provides high‑stiffness diaphragm action, efficient load transfer, exceptional torsional resistance, long‑span capability (98‑meter radial reach), and extreme durability with a 150+ year design life.
