MMC-VB and MMC-VC Viaduct Engineering

Pylon geometry, cap beam and girder design, HVDC arm loading, longitudinal wire-rope continuity system.

MEMO 6 — MMC-VB AND MMC-VC VIADUCT ENGINEERING — PRE-FEASIBILITY — INTERNAL WORKING DOCUMENT

SOVEREIGN BUILD CORPORATION

Memo 6 — MMC Viaduct Engineering

MMC-VB and MMC-VC Pylon Spec — Pre-Feasibility Structural Model

Dual-leg two-level viaduct for Phase 0 (Melbourne–Brisbane) and single-leg single-deck viaduct for Phase 0.2 (Newcastle–Sydney Direct). Both built from the same 4m standard foundation and the same MMC pylon segment family.

Brett Murrell — Inventor & Candidate, Robertson

May 2026 — INTERNAL WORKING DOCUMENT — PRE-FEASIBILITY GRADE

1. Introduction — One Platform, Two Configurations

The MMC structural platform is defined by a fixed set of architectural primitives — foundation, pylon segments, cap beams, and longitudinal girders — that combine in different configurations to produce every deployment type. This memo models two specific configurations at pre-feasibility grade:

2. Shared Foundation — The Standard 4m Caisson

Both Pylon B and Pylon C use the identical foundation system. The 4m OD caisson is the standard MMC foundation — drilled by the same rig, assembled from the same ring segment family, anchored by the same cutter head. The only difference is quantity: Pylon B requires two caissons per pylon location (one per leg); Pylon C requires one.

Tubular sizing note: Pylon B uses 20" × 171ppf L80 13Cr (2.35t per 12m joint) — load demands and dual-leg platform justify this size. Pylon C (Phase 0.2) uses 13.375" × 72ppf L80 13Cr (1.26t per 12m joint) — structurally adequate at all Phase 0.2 heights (7.0 MN joint capacity vs near-zero tension demand) and significantly better handling on a narrow single-leg elevated work platform. The handling argument is decisive for Phase 0.2: installing 2.35t joints on a single-leg platform at 30-70m is a major rigging operation; 1.26t joints are manageable with standard pipe-handling equipment. Both grades are L80 13Cr API 5CT — same material specification, different wall thickness.

Foundation depth is the single largest design variable. Geology along the Phase 0 inland corridor is predominantly alluvial and sedimentary — likely 5–10m adequate at most locations. Hard rock sections and river crossings may require 15–20m+. The ring segment count scales directly with depth: each additional metre of depth = one additional ring segment per leg. The Megafactory produces rings at the same rate regardless of depth specification.

3. Pylon B — MMC-VB Dual-Leg Two-Level Viaduct

Pylon B is the Phase 0 standard — the dual-leg two-level viaduct that carries ten integrated services along the Melbourne to Brisbane inland spine. Two parallel pylon legs, spaced 8m centre-to-centre (inside), with a 17m total corridor width. Stage 1 builds the freight deck at 6m; Stage 2 adds the maglev deck at 17m above ground.

MMC-VB dual-leg two-level viaduct — Phase 0 standard configuration. Two legs, two decks, gold HVDC arm brackets. SketchUp pre-feasibility model — not to final engineering specification.

3.1 Pylon B Geometry

3.2 Stage 1 — Freight Viaduct (Deck at 6m)

3.3 Stage 2 — Upper Structure (Maglev Deck at 17m)

Stage 2 is built on the commissioned freight corridor — the rail crane operates on the running freight deck, lifting upper structure components from flatbed rail wagons. The freight corridor funds and supplies its own upper-level construction.

3.4 Pylon B Weight Summary

The non-concrete elements account for approximately 45% of total span weight. The two 20" L80 13Cr tubulars alone contribute ~200t (each tubular runs the full height — foundation depth + pylon height ≈ 30-35m at ~6t/m). HVDC arms, cross-bracing, rail, track, and services make up the remainder.

3.5 HVDC Transmission Loading — MMC-VB

MMC-VB carries four HVDC bipole circuits — 72GW total at ±800kV ultra-high voltage. The HVDC arms are steel fabrications with sockets cast into HB1 (and HB3 for upper circuits) via the P#7 rib at factory precision. The arm loads transfer directly into the cap beams and thence into the pylon legs via the tubular tension element. HVDC loading must be considered alongside structural dead and live loads in the HB1 cap beam and arm socket design.

3.6 Pylon B Module Count — Phase 0

4. Pylon C — MMC-VC Single-Leg Single-Deck Viaduct

Pylon C is the Phase 0.2 configuration — the simplest MMC structural form. One leg per pylon, one deck level. Same foundation caisson, same pylon segment family, same Megafactory. The single-leg configuration reduces the per-pylon concrete weight by approximately 60% compared to Pylon B at standard height, and the variable-height capability means the same pylon serves both flat plains (6m) and deep valley crossings (70m+) with the same production unit.

MMC viaduct configuration family. Pylon C (Phase 0.2) is the Single Leg Single-Deck configuration (far left) — one caisson, one column, one cap beam, three girders. Pylon B (Phase 0 MMC-VB) is the Dual Leg 2-Deck configuration (third from left) — two caissons, two column stacks, freight deck at 6m and maglev deck at 17m. HB1 cap beam shown in green; deck girders and elements in pink. All configurations share the same foundation, segment, and cap beam production catalogue.

4.1 Pylon C Geometry

4.2 Pylon C — Variable Height Capability

The defining feature of Pylon C for Phase 0.2 is variable height. The ridge-riding route between Newcastle and Sydney has terrain ranging from flat Hunter Valley plains to high ridge crossings at 286m elevation (Google Maps verified). The same P1 column segment — 3m long, tapered, produced by the Megafactory in 33 die profiles — stacks to whatever height the terrain requires.

4.3 Pylon C Structure

4.4 Pylon C Weight Summary

Pylon C at standard height (347t) is approximately 40% of the concrete mass of Pylon B (865t). At deep valley crossings (815t) the Pylon C approaches Pylon B weight — but these are exceptional spans. The Phase 0.2 route has median terrain elevation of 62m above sea level, meaning most pylons ride the ridgeline at modest height above the ridge surface (6–20m), keeping the average pylon weight well below Pylon B.

4.5 Pylon C Module Count — Phase 0.2

5. Pylon B vs Pylon C — Direct Comparison

6. Shared Production — One Factory, Both Pylons

The economic case for Phase 0.2 rests on the shared production argument. Every module type in Pylon C is a subset of the Pylon B module catalogue. The Megafactory does not need new tooling, new dies, new jigs, or new production lines to produce Pylon C modules. They are already in production for Phase 0.

6.1 Production Rate Impact

Phase 0 requires 1,473 modules per day over Stage 1 (5 years). Phase 0.2 requires approximately 106,560 modules total — approximately 73 production days at Phase 0 rate. The sequencing is entirely manageable: Phase 0.2 modules are produced during Phase 0's operational ramp-up period or as an additional production run from the Line 3 girder line (which runs at 55% utilisation in Phase 0 and has headroom for Phase 0.2 orders).

7. MMC-T Transmission — Module Lists

The MMC-TA and MMC-TB transmission tower configurations share the same foundation and pylon segment family as MMC-VB and MMC-VC. The distinctive elements are the saddle column segment (P1-S) at arm height — which has a half-circle recess on the arm-bearing face to seat the bolt-on cross-arm — and the cross-arm modules themselves (XA-A for dual-tower portal, XA-B for single-leg). All other modules are identical to the MMC-V pylon family.

7.1 MMC-TA — Dual-Tower Portal

7.2 MMC-TB — Single-Leg Tower

8. Longitudinal Wire Rope Continuity System

Each 25m girder span is designed as a simply-supported element for gravity loads, carried by the internal pre-tensioned strand family. A supplementary longitudinal wire rope system threads continuously through all girder spans to provide structural continuity, thermal restraint, and joint pre-compression across the full corridor length.

8.1 Concept

A continuous stainless steel wire rope runs through a smooth circular duct cast into each girder via the P#7 rib — one rope per girder, at factory-precision position. The rope threads through successive spans as the construction front advances, and is tensioned to working load before the next span is placed. Every completed span is immediately at full structural capacity. There are no weak sections at any point during construction.

8.2 Installation Concept

10 rope spools are mounted on a rail trolley riding on the commissioned freight deck behind the construction front — one spool per girder. As each new span is placed and its duct aligned with the previous span, the rope feeds forward from the spool through the new girder duct. The spool tensioning system applies working load. The construction front advances. The rope extends span by span, always under tension, always at working load.

8.3 Engineering Design Items — Pending

The wire rope continuity concept is locked. The detailed installation methodology and spool logistics are flagged for engineering design. Key constraints to resolve:

Longitudinal wire rope continuity system — concept locked. Installation methodology, spool logistics, tensioning sequence, and relay anchor spacing require detailed engineering design. Flagged for structural and construction engineers at detailed design stage.

9. Engineering Caveats and Next Steps

This memo is pre-feasibility grade. Numbers are within ±20–30% of detailed design values and are suitable for programme planning, cost estimation, and investment discussion. The following issues require resolution at detailed design stage before any binding structural commitments:

Pre-feasibility grade — numbers within ±20–30% of detailed design values. Detailed structural engineering by qualified engineers per AS/NZS 7000:2016, AS 3600, and AS 1170 required before any binding use. Contact brett.murrell21@gmail.com for technical enquiries.

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