4.1 System Overview
Section 4 defines the primary lateral load‑resisting enhancement system of the 900‑meter helical supertall. It consists of outrigger trusses connecting the central core to the perimeter frame, and belt truss mega‑rings acting as circumferential stiffeners.
Primary Structural Role
- Reduces overturning moment
- Reduces lateral drift
- Reduces core rotation
- Couples stiffness between core and perimeter mega‑frame
- Acts as a global stiffness amplifier
- Redistributes loads across the structural system
4.2 System Distribution (Vertical)
| Outrigger Levels | Every 20 stories (10 levels total) |
|---|---|
| Belt Truss Levels | Every 10 stories (5 levels total) |
| Total Building Height | 900 m |
| Floor Height | 4.5 m |
| Total Floors | 200 |
4.3 Global Geometry
| Core diameter | Ø24,000 mm |
|---|---|
| Building diameter (base) | Ø220,000 mm |
| Outrigger truss length | 44,000 mm |
| Outrigger truss depth | 8,000 mm |
| Belt truss segment length | 22,000 mm |
| Belt truss depth | 6,000 mm |
4.4 Outrigger System Configuration
Structural Type
- Vierendeel‑type truss system
- Rigid frame behavior (no diagonal triangulation in primary form)
Primary Components
1. Central Core
- Material: Duplex Stainless Steel
- Diameter: Ø24,000 mm
2. Outrigger Truss
- Length: 44,000 mm
- Depth: 8,000 mm
3. Truss Members (Per Truss)
| Top chord | Ø1,016 mm × 40 mm — Qty: 2 |
|---|---|
| Bottom chord | Ø1,016 mm × 40 mm — Qty: 2 |
| Vertical posts | Ø508 mm × 25 mm — Qty: 4 |
| Diagonal members | Ø508 mm × 25 mm — Qty: 4 |
| Material | Duplex Stainless Steel (EN 1.4462) |
Engineering Behavior
- Transfers moment from core to perimeter
- Converts core bending into axial forces in perimeter columns
- Functions as a stiff horizontal lever arm
4.5 Outrigger Node Connection (Core Interface)
Node Components
- Core wall interface (Ø24 m)
- Upper and lower CNC‑machined node rings
- Connection plates and stiffeners
- Diagonal brace interfaces
Node Dimensions
| Node ring diameter | Ø2,100 mm |
|---|---|
| Node ring thickness | 80 mm |
| Chord tube diameter | Ø1,016 mm |
| Chord thickness | 40 mm |
| Brace diameter | Ø508 mm |
| Brace thickness | 25 mm |
Connection System
- Bolt type: M64 (Grade 8.8)
- Weld type: Full penetration groove weld
- Stiffener plates welded
4.6 Outrigger Plan Geometry
Radial layout around core connecting core → inner ring → mega frame.
| Core diameter | Ø24,000 mm |
|---|---|
| Building diameter | Ø220,000 mm |
4.7 Belt Truss System
Structural Role
- Circumferential mega‑ring
- Load redistribution system
- Connects all perimeter columns
Belt Truss Geometry
| Segment length | 22,000 mm |
|---|---|
| Truss depth | 6,000 mm |
Member Schedule (Per Segment)
| Top chord | Ø1,219 mm × 45 mm — Qty: 1 |
|---|---|
| Bottom chord | Ø1,219 mm × 45 mm — Qty: 1 |
| Diagonals | Ø762 mm × 30 mm — Qty: 4 |
| Vertical posts | Ø610 mm × 25 mm — Qty: 2 |
| Material | Duplex Stainless Steel |
4.8 Belt Truss Connection to Helical Frame
Connection Components
- Belt truss chord
- Gusset plate
- Helical frame tube
- High‑strength bolts (M64)
- Full penetration welds
Connection Data
| Bolt size | M64 (Grade 8.8) |
|---|---|
| Bolt hole diameter | Ø68 mm |
| Gusset plate thickness | 50 mm |
| Weld type | Full penetration groove weld |
4.9 Load Transfer Mechanism
Outrigger Action
- Core resists bending
- Outriggers engage perimeter columns
- Perimeter columns develop tension (windward) and compression (leeward)
Belt Truss Action
- Redistributes forces circumferentially
- Prevents local overstressing
- Prevents uneven column loading
4.10 Performance Improvement
| Lateral stiffness increase | 45–60% |
|---|---|
| Top displacement reduction | 35–50% |
| Overturning moment reduction | 40–55% |
4.11 Construction Logic
Sequence
- Core constructed first
- Outrigger nodes installed
- Truss segments lifted and connected
- Belt trusses installed
- Connections fully welded and tensioned
Integration
- Fully synchronized with:
- Floor modules (Section 2)
- Radial truss system (Section 3)
4.12 Fabrication & Material Notes
- All members: Duplex Stainless Steel EN 1.4462
- All tubes: seamless
- All welds: full penetration, ground, and passivated
- Connections: welded + bolted hybrid
- Fabrication tolerance: ±5 mm
- Installation tolerance: ±10 mm
4.13 Engineering Logic Summary
Why Outriggers Work
- Increase effective structural width
- Convert core bending into global axial system
Why Belt Trusses Are Critical
- Tie entire perimeter into a single structural ring
- Prevent differential movement
- Enhance redundancy
System Synergy
- Core = stiffness spine
- Outriggers = load transfer arms
- Belt truss = perimeter lock
Together, these create a highly efficient mega‑tall structural system.
4.14 System Summary
The Outrigger & Belt Truss System is essential for the stability of a 900‑meter structure. It provides wind and seismic resistance, drift control, and structural efficiency at extreme heights.
