Case Study

Gateway South
(Darlington Upgrade)

Client: Laing O'Rourke / DITDarlington, AdelaideStructural Engineer / Structures Manager

Gateway South Darlington bridge segment moved by Self-Propelled Modular Transporter

780T bridge superstructure on SPMT — Darlington (2018)

Project Overview

The Gateway South project delivered a grade-separated interchange at the junction of South Road, Flagstaff Road, and the Southern Expressway in Darlington, removing one of Adelaide's most congested bottlenecks. Delivered by Laing O'Rourke for the Department for Infrastructure and Transport (formerly DPTI), the project involved lowering South Road beneath the existing surface level, constructing new bridge structures at the interchange, and upgrading surrounding road connections.

Jerome served as Structural Engineer and subsequently Structures Manager, overseeing the full spectrum of structural work packages from design coordination through construction completion. The role encompassed FRP (fibre-reinforced polymer) substructure works, architectural fascia wall design and installation coordination, bridge deck construction, and structural quality management across the interchange.

The project presented significant constructability challenges due to its location at a major urban intersection, requiring staged construction that maintained traffic flow on all approach roads. The structural works involved deep excavation adjacent to existing services, complex temporary works for bridge construction over live traffic lanes, and the integration of architectural finishes with structural elements to a standard not previously achieved on South Australian road projects.

Scope of Work

JCY delivered structural engineering and management services including:

Structural work package coordination across all bridge and retaining wall elements
FRP (fibre-reinforced polymer) substructure design coordination and installation oversight
Architectural fascia wall system design interface and installation management
Bridge deck construction supervision including formwork, reinforcement, and concrete placement
Temporary works design review and approval for falsework and propping systems
Structural steel connection detailing review and welding inspection coordination
Reinforcement scheduling review and site placement verification
Concrete mix design review, trial placements, and quality control monitoring
Structural element survey and dimensional compliance checking
Interface management between structural works, civil earthworks, and services installation

Key Challenges & Solutions

Challenge

FRP Substructure Integration

The Gateway South design incorporated fibre-reinforced polymer (FRP) elements within the bridge substructure, a material system requiring specialist installation techniques and quality verification procedures not covered by conventional reinforced concrete standards. Jerome coordinated between the FRP manufacturer, the design team, and site crews to develop bespoke installation procedures, including surface preparation protocols, adhesive application methods, and load testing sequences. Each FRP installation was documented with photographic records and test certificates to build a quality evidence package for the asset owner.

Challenge

Architectural Fascia Walls

The interchange design required architectural fascia walls that served both structural retaining and aesthetic functions, with exposed concrete finishes requiring Class 2 or better surface quality. Achieving consistent architectural finishes across large poured elements demanded precise formwork fabrication, controlled concrete placement rates, and specific curing regimes. Jerome implemented staged mock-up panels to confirm finish quality before committing to production pours, and established pour-specific quality checklists covering vibration patterns, formwork release agent application, and curing membrane timing.

Challenge

Deep Excavation Adjacent to Services

Lowering South Road required deep excavation within metres of major trunk services including 1500mm diameter water mains, high-voltage electrical cables, and telecommunications conduits. The structural retaining system had to be installed in a sequence that maintained ground support to these services at all times. Jerome coordinated the structural construction sequence with utility protection works, specifying soldier pile installation depths and waler activation stages that kept lateral ground movements below the service owner's displacement tolerances throughout excavation.