2024
Western Cape

The Carinus Bridge, a vital 175m long crossing over the Berg River, connects Velddrif to the West Coast Peninsula. Serving as a critical transportation link since its construction in 1950, the bridge features simply supported rib-beam decks with an 18m drop-in span supported by half-joints. While this design was popular at its time, allowing articulation and reducing restraint forces, it introduced significant vulnerabilities that worsened over decades of service.

Structural Strengthening of Carinus bridge.

Project Overview

Routine inspections revealed severe deterioration in the half-joints of the main span (Span 6), including cracking, spalling, and a concerning 20mm vertical displacement at Half-Joint 2. Additionally, chloride-induced corrosion of the bridge’s reinforcement and inadequate structural redundancy exacerbated the degradation.

Recognising the need for urgent intervention, the Western Cape Government’s Transport Infrastructure Branch commissioned a collaborative effort with consultant AECOM SA and contractor Smart Civils Construction. Sika South Africa was subsequently appointed by the contractor for the supply of proprietary and specialised strengthening products. Together, they implemented innovative structural safeguarding measures designed to stabilise the bridge and extend its lifespan until a replacement could be constructed.

Innovative Interventions

AECOM SA conducted a thorough assessment using retrospective design checks and Non-Destructive Testing (NDT) methods, identifying critical structural shortcomings. A suite of advanced solutions was employed to address these issues:

1.     Bending Capacity Enhancement

Carbon Fibre Reinforced Plates (CFRP) were applied to the sagging and hogging regions of Span 6.
These included:
Sika® CarboDur® S626 plates: 448m for external soffit reinforcement.
Sika® CarboDur® S NSM plates: 320m for Near Surface Mounted reinforcement.
CFRP plates were adhered using Sikadur®-30 epoxy adhesive, while SikaWrap®-300 C fabric and SikaWrap® FX-50C cords provided debonding and delamination prevention.

3.     Diaphragm Strengthening
Core-drilled holes allowed for the installation of high-strength Dywidag WR 950/1050MPa prestress threadbar.
The diaphragm thickness was increased by casting 400mm thick reinforced concrete diaphragm thickenings on either side of each half-joint using Self-Compacting Concrete (SCC).

2.     Half-Joint Rehabilitation

The expansion joint gaps of the deteriorated half-joints were injected with a proprietary cementitious grout to restore structural integrity.
Temporary restraints prevented destabilisation during the grout injection process, ensuring the safety and stability of the drop-in span until the grout cured.

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Corrosion protection done with Sika products on Carinus Bridge. Western Cape
Image: Longitudinal threaded stress bars with corrosion protection.
Soffit strengthening with Sika CFRP plates and fabric. Carinus Bridge Project
Image: Soffit strengthening using external CFRP materials and intermediate carbon fibre fabric.
Diaphragm thickening reinforcement with cored hole
Image: Diaphragm thickening reinforcement with cored hole before casting SCC through the top slab.

Community Upliftment

  • Over 3,000 person-days of work were provided to local labourers, contributing to job creation.
  • Local labourers received formal training through various accredited training courses that were arranged by the Contractor.
  • R2.56 million of the project budget was allocated to Targeted Enterprises, demonstrating a strong commitment to social responsibility in the form of community upliftment, aligning with the Client's Broad-Based Black Economic Empowerment (B-BBEE) specifications.

Exemplary Safety Standards

The project achieved an impeccable safety record, with no Section 24 incidents or accidents reported, underscoring its commitment to rigorous health and safety practices.

Environmental Responsibility

The bridge’s location within a sensitive Estuarine Functional Zone necessitated strict adherence to the National Environmental Management Act (NEMA). Unique measures to minimise environmental impacts included:

  • Suspended access scaffolding to avoid disturbance to the riverbed. 
  • Rigorous containment protocols for epoxy adhesives, coatings, and concrete coring debris to prevent contamination.

Critically acclaimed

The Carinus Bridge Structural Holding Measures Project received two "Highly Commended" awards at the 2024 Best Projects Awards Ceremony:

  1. Specialist Suppliers Category
  2. Consulting Engineers Category
Conclusion

The Carinus Bridge Structural Holding Measures Project exemplifies excellence in infrastructure maintenance. By combining advanced materials, innovative engineering techniques, and a commitment to community and environmental sustainability, the project ensured the continued safety and functionality of a vital transportation link.