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Engineered maintenance of port wharf structures

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Author(s): Scott Bacon, Newcastle Port Corporation with Warren Green, Vinsi Partners Consulting Engineers, Sydney and Brad Dockrill, Vinsi Partners Consulting Engineers, Newcastle, Australia

Introduction

Exporting over 103 million tonnes per annum, the Port of Newcastle, New South Wales, Australia is one of the world’s largest single coal export ports. In addition to coal, the port handles over 40 different non-coal commodities. Forecasts indicate that Newcastle Port Corporation (NPC) can expect to exceed 180 million tonnes per annum by 2015 in coal trade alone.

Newcastle Port Corporation operates 365 days a year, 24 hours a day. It has 18 operational berths, seven dedicated to the handling of coal and 11 allocated to the handling of non-coal trade. NPC also owns, operates and maintains 195 navigation aids, 16 kilometers of roads, 4.5 kilometers of rail, 51 buildings, two breakwaters and over 7 kilometers of seawalls. Heritage structures near the entrance to the port also fall within the NPC asset register.

The port’s assets are located in an aggressive marine environment so the corporation is acutely aware of corrosioninduced deterioration and the need for corrosion management and maintenance approaches to sustaining the service lives of structural and building assets.

Port of Newcastle wharf and berth structures

The wharf and berth structures of the Port of Newcastle are of reinforced concrete construction (decks, substructure beams and rear walls) supported on reinforced concrete or steel piles. The berth, wharf and jetty structures that NPC are directly responsible for are summarized below (see Table 1). Other berth and wharf structures within the port are leased and are the responsibility of the tenants. The age of the NPC wharf and berth structures varies from 32 to 63 years, some are therefore at or beyond their designed lives. However, decades of future service lives are required of the structures so pro-active, engineered, maintenance and corrosion management is necessary.

Condition assessment of structures

Condition surveys have been necessary for all structures so as to determine the mechanisms and extent of deterioration and enable prognoses of future deterioration. Structural assessments and structural capacity checks have also typically been undertaken. Scenario analyses of remedial, maintenance and corrosion management options have been utilized. Informed decisions have therefore been possible by NPC.

Various consulting engineers have worked with the corporation to undertake the condition surveys, structural assessments and remedial options analysis. The independence of these consulting engineers has been paramount as conflicts of interest associated with the supply of materials, equipment or laboratory testing services would compromise recommendations.

Maintenance and corrosion management approaches

The maintenance and corrosion management approaches being adopted by NPC for substructure elements of wharf and berth structures have been engineered and tailored to meet required future structure service lives, budgetary constraints, release of maintenance funding and lowest life cycle costs.

The maintenance and corrosion management approaches being adopted include:

Doing nothing in some cases; penetrant treatment (and re-application) of select concrete elements to prevent reinforcement corrosion initiation; conventional concrete repair; impressed current Cathodic Protection (CP) of select concrete elements and petrolatum tape wrapping to mean low water level (MLW) of steel tubular or steel H-section (UC or UBP) piles. Also, CP (galvanic or impressed current) for in-water steel pile sections or various combinations of these methods.

These approaches have only been applied to those wharf and berth substructure elements that need them. For example, there is not a need to cathodically protect the whole reinforced concrete substructure sections of any berths, only those elements that need CP. Combinations of remedial options are routinely utilized.

Concrete CP systems overview

Impressed current anode systems include catalysed titanium ribbon mesh, mixed metal oxide coated ribbon and discrete anodes (proprietary and tailor-made). Transformer rectifier units (TR units) vary in number and type. Remote monitoring and control systems (RMCS) were installed to some TR units.

 

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