AS 4997-2005

AS 4997—2005

Australian Standard™

Guidelines for the design of maritime structures

AS 4997—2005

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This Australian Standard was prepared by Committee CE-030, Maritime Structures. It was approved on behalf of the Council of Standards Australia on 29 March 2005. This Standard was published on 28 September 2005.

The following are represented on Committee CE-030:

Association of Australian Ports and Marine Authorities Association of Consulting Engineers Australia Australian Stainless Steel Development Association Boating Industry Association of Australia Cement Concrete & Aggregates Australia – Cement Civil Contractors Federation Engineers Australia Institute of Public Works Engineering Australia Marina Association of Australia Monash University Queensland Transport University of Wollongong

Keeping Standards up-to-date Standards are living documents which reflect progress in science, technology and systems. To maintain their currency, all Standards are periodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. It is important that readers assure themselves they are using a current Standard, which should include any amendments which may have been published since the Standard was purchased. Detailed information about Standards can be found by visiting the Standards Web Shop at www.standards.com.au and looking up the relevant Standard in the on-line catalogue. Alternatively, the printed Catalogue provides information current at 1 January each year, and the monthly magazine, The Global Standard, has a full listing of revisions and amendments published each month. Australian StandardsTM and other products and services developed by Standards Australia are published and distributed under contract by SAI Global, which operates the Standards Web Shop. We also welcome suggestions for improvement in our Standards, and especially encourage readers to notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at [email protected], or write to the Chief Executive, Standards Australia, GPO Box 476, Sydney, NSW 2001.

This Standard was issued in draft form for comment as DR 02536.

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AS 4997—2005

Australian Standard™


First published as AS 4997—2005.

COPYRIGHT © Standards Australia All rights are reserved. No part of this work may be reproduced or copied in any form or by any means, electronic or mechanical, including photocopying, without the written permission of the publisher. Published by Standards Australia, GPO Box 476, Sydney, NSW 2001, Australia ISBN 0 7337 6858 X A

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PREFACE This Standard was prepared by Standards Australia Committee CE-030, Maritime Structures. The objective of this Standard it to provide designers and regulatory authorities of structures located in the marine environment with a set of guidelines and recommendations for the design, preservation and practical applications of such structures. These structures can include fixed moorings for the berthing of vessels, piles and other parts of a substructure, wharf and jetty decks, building substructures over waters, etc. This Standard has been prepared as a guideline only, to provide advice and recommendations for maritime structures. Clauses in this document are written using informative terminology and should not be interpreted otherwise. The requirements of a maritime structure and its associated facilities should be determined for the individual application. This Standard should be used in conjunction with the relevant materials and design Standards.

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CONTENTS

Page SECTION 1 SCOPE AND GENERAL

1.1 SCOPE ........................................................................................................................ 5 1.2 REFERENCED AND RELATED DOCUMENTS ...................................................... 6 1.3 NOTATION ................................................................................................................ 7 1.4 DEFINITIONS ............................................................................................................ 8

SECTION 2 SITE INVESTIGATION AND PLANNING 2.1 GENERAL ................................................................................................................ 10 2.2 SURVEY................................................................................................................... 10 2.3 GEOTECHNICAL..................................................................................................... 11 2.4 ASSESSMENT OF LOADS...................................................................................... 11

SECTION 3 DIMENSIONAL CRITERIA 3.1 STRUCTURE HEIGHTS .......................................................................................... 12 3.2 FENDER HEIGHTS.................................................................................................. 12 3.3 LAYOUT OF BERTH STRUCTURES ..................................................................... 12 3.4 ACCESS AND SAFETY........................................................................................... 13

SECTION 4 DESIGN REQUIREMENTS 4.1 AIM ........................................................................................................................... 14 4.2 DESIGN REQUIREMENTS ..................................................................................... 14 4.3 FLOATING STRUCTURES ..................................................................................... 15 4.4 BREAKWATERS ..................................................................................................... 15 4.5 EFFECTS OF SCOUR AND SILTATION................................................................ 16 4.6 SEA LEVEL RISE (global warming) ........................................................................ 16

SECTION 5 DESIGN ACTIONS 5.1 GENERAL ................................................................................................................ 17 5.2 PERMANENT ACTIONS (DEAD LOADS)............................................................. 17 5.3 IMPOSED ACTIONS (LIVE LOADS) ..................................................................... 17 5.4 WIND ACTIONS ...................................................................................................... 21 5.5 CURRENT ACTIONS............................................................................................... 22 5.6 DEBRIS ACTIONS................................................................................................... 23 5.7 NEGATIVE LIFT DUE TO CURRENTS ................................................................. 23 5.8 HYDROSTATIC ACTIONS ..................................................................................... 23 5.9 WAVE ACTIONS ..................................................................................................... 24 5.10 CONSTRUCTION AND MAINTENANCE ACTIONS ............................................ 26 5.11 LATERAL EARTH ACTIONS ................................................................................. 26 5.12 COMBINATIONS OF ACTIONS ............................................................................. 26 5.13 PROPELLER WASH ................................................................................................ 28 5.14 EARTHQUAKE ACTIONS ...................................................................................... 28

SECTION 6 DURABILITY 6.1 GENERAL ................................................................................................................ 30 6.2 DESIGN LIFE ........................................................................................................... 30 6.3 CONCRETE .............................................................................................................. 33 6.4 STEEL....................................................................................................................... 38 6.5 TIMBER.................................................................................................................... 41

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APPENDICES A CONTAINER WHARF DECK LOADINGS............................................................. 43 B BERTHING ENERGIES AND LOADS.................................................................... 46 C MOORING LOADS .................................................................................................. 50

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www.standards.com.au Standards Australia

STANDARDS AUSTRALIA Australian Standard


S E C T I O N 1 S C O P E A N D G E N E R A L

1.1 SCOPE This Standard sets out guidelines for the design of structures in a marine environment. It is to be used in conjunction with the relevant Standards and provides recommendations additional to the requirements of these Standards. This Standard is intended to cover the design of near-shore coastal and estuarine structures, such as— (a) jetties; (b) wharves; (c) berthing dolphins; (d) floating berths; (e) seawalls; (f) breakwater structures, excluding rubble mound and floating types; (g) boat ramps; (h) laterally restrained floating structures; and (i) building substructures over water. This Standard is not intended to cover the design of— (A) pipelines; (B) marinas (see AS 3962); (C) offshore oil and gas structures; (D) dredging and reclamation; (E) coastal engineering structures such as rock armoured walls, groynes, etc; (F) geometrical design of port and harbour infrastructure; (G) floating structures not permanently restrained, e.g., vessels, construction pontoons,

barges. For buildings constructed over water, these guidelines apply to the structure up to and including the main deck level. The superstructure above main deck level should be designed in accordance with the relevant Australian Standards and relevant building regulations.

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Standards Australia www.standards.com.au

1.2 REFERENCED AND RELATED DOCUMENTS 1.2.1 Referenced documents The following documents are referenced in this Standard: AS 1012 Methods of testing concrete 1012.13 Method 13: Determination of the drying shrinkage of concrete for samples

prepared in the field or in the laboratory. 1170 Minimum design loads on structures 1170.4 Part 4: Earthquake design loads on structures 1604 Timber—Preservative-treated—Sawn and round 1657 Fixed platforms, walkways, stairways and ladders—Design, construction and

installation 3600 Concrete structures 3962 Guidelines for design of marinas 3972 Portland and blended cement 4100 Steel structures 5100 Bridge design 5100.2 Part 2: Design loads 5604 Timber—Natural durability ratings AS/NZS 1170 Structural design actions 1170.0 General principles 1170.1 Part 1: Permanent, imposed and other actions 1170.2 Part 2: Wind actions 1554 Structural steel welding 1554.6 Part 6: Welding stainless steels for structural purposes 2312 Guide to the protection of iron and steel against exterior atmospheric corrosion 2832 Cathodic protection of metals (all parts) 4671 Steel reinforcing materials 4673 Cold formed stainless steel structures 4680 Hot-dip galvanized (zinc) coatings on fabricated ferrous articles BS 6349 Maritime structures (all parts) 6744 Stainless steel bars for the reinforcement and use in concrete – Requirements

and test methods Disability Standards for Accessible Transport (Australian Government) PIANC Design of fender systems—2002 1.2.2 Related documents AS/NZS 1664 Aluminium structures AS 5100 Bridge design (all parts) SA HB 84 Guide to Concrete Repair and Protection A

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1.3 NOTATION 1.3.1 Abbreviations The following abbreviations are used in this Standard. AHD = Australian Height Datum CD = Chart Datum, used for the preparation of navigation charts, and usually about

the same level as LAT CQC = Container Quay Crane (Portainer crane, ship-to-shore crane) DWT = Dead Weight Tonnage (The total mass of cargo, stores, fuels, crew and reserves

with which a vessel is laden when submerged to the summer loading line.) NOTE: Although this represents the load carrying capacity of the vessel it is not the exact measure of cargo load.

GRT = Gross Registered Tonnage (The gross internal volumetric capacity of the vessel as defined by the rules of the registering authority and measured in units of 2.83 m3 (100 ft3)).

HAT = Highest Astronomical Tide (see Clause 3.2) ISLW = Indian Spring Low Water (Obsolete estimate of Lowest Astronomical Tide

(LAT) formerly used as chart datum) LAT = Lowest Astronomical Tide (Now adopted as chart datum for all Australian

Hydrographic Charts (see Clause 3.2)) LOA = Length Overall of a vessel, measured to the extremities of fittings. MSL = Mean Sea Level, usually about the same level as AHD 1.3.2 Symbols The following symbols are used in this Standard. db = reinforcing bar diameter Ed = design action effect Ed,dsb = design action effects destabilizing structure Ed,stb = design action effects stabilizing structure Es = serviceability earthquake action Eu = ultimate earthquake action f = co-efficient of wave height (see Clause 5.9.1) f′c = characteristic compressive strength of concrete, in Megapascals (MPa) fs = steel reinforcing stress, in Megapascals Fb = berthing impact loads Fb,u = berthing impact actions under abnormal conditions FD = action in the direction of wind, in kilonewtons (kN) Fe = earth pressure loads Fenv = combined environmental loads

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Fgw = ground water loads Flat = minimum lateral load (see Clause 5.3.1) Flp = liquid pressure load Fm = mooring loads Fs = stream flow loads, including debris loads Fwave.S = wave loads under serviceability conditions (1 in 1 year) Fwave.U = wave load under ultimate strength conditions g = acceleration due to gravity G = permanent action (dead load) H1 = wave height used for design of structures (see Clause 1.4.3) Hs = significant wave height (see Clause 1.4.5) P = pressure, in kilopascals (kPa) Q = imposed action (live load) Su = loading combination (see Clause 5.12.4) Ts = period of significant waves Ws = wind load for serviceability limit state Wu = wind load for strength limit state V = design wind speed, in metres per second v = current velocity, in metres per second

1.4 DEFINITIONS For the purpose of this Standard, the definitions below apply. 1.4.1 Action Set of concentrated or distributed forces acting on a structure (direct action), or deformation imposed on a structure or constrained within it (indirect action).

NOTE: The term load is often used to describe direct actions. 1.4.2 Design life The period for which a structure or a structural element remains fit for use for its intended purpose with appropriate maintenance (see Clause 6.2). 1.4.3 Design wave (H1) The highest 1% of waves in any given time interval. Used, for example, in the analysis of structures. 1.4.4 Load The value of a force appropriate to an action. 1.4.5 Significant wave height (Hs) The average height of the highest one-third of waves in any given time interval. It approximates the wave height for this train of waves as estimated by an expert observer. A

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1.4.6 Sponson Rubbing strip, generally at main deck level, to strengthen and protect vessel from berthing impacts. 1.4.7 Swell waves Waves generated some distance from the site; no longer under the influence of generating wind. 1.4.8 Vessel displacement The total mass of a vessel and its contents.

NOTE: This is equal to the volume of water displaced by the vessel multiplied by the density of the water.

1.4.9 Vessel wash Waves formed by the passage of a vessel. 1.4.10 Wind wave Waves formed under the influence of local generating winds, usually called seas.

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S E C T I O N 2 S I T E I N V E S T I G A T I O N A N D P L A N N I N G

2.1 GENERAL In maritime structures, the effect of the local environment and geographical configurations (including the new configuration after completion of the proposed maritime facility) has significant bearing on the performance of the structures. Detailed site investigations are an essential part of the planning and design of maritime facilities. Thus, for any site on which it is proposed to install a maritime structure, a detailed site investigation should be undertaken to provide sufficient information for the design and construction of the structure. Maritime structures that have the potential to obstruct currents and waves are likely to affect the littoral processes and the effect of such structures on the adjacent natural features must be investigated. Hydrographic and terrestrial surveys should be undertaken. Such surveys and subsequent investigations (e.g., geotechnical) should adopt a uniform survey grid. The wind, wave, current, berthing and other actions that may be applicable to the structure should be considered in the site investigation.

2.2 SURVEY 2.2.1 Survey grid A uniform survey grid should be adopted for the project area. All terrestrial and hydrographic surveys should use this survey grid. Consideration should be given to incorporating the survey grid for the project area into the regional coordinated survey grid, e.g., International Survey Grid or Map Grid of Australia 1994 (MGA94), for projects in Australia. Where a local survey grid is adopted, this should be clearly noted on the drawings and the correlation to GRS80 or WGS84 grid should be nominated on the drawings. 2.2.2 Survey datum All survey data should be reduced to a recognized datum, which may be Chart Datum (CD) or Australian Height Datum (AHD). Chart Datum is the preferred datum for surveys and mapping of maritime works and offshore topography, as it provides direct correlation to navigable water depths. The correlation between CD and AHD for the specific location should be clearly shown on all the drawings, e.g., by a note or a diagram. 2.2.3 Hydrographic survey The hydrographic survey should be undertaken to cover the proposed site of works and any adjacent near-shore water up to mean high water level, including adjacent navigable waterways where there is insufficient existing survey data to make an appropriate assessment of design waves, currents and other pertinent analysis and design parameters. The survey data should also contain sufficient detail to enable an assessment of the hydraulic and seabed processes affecting the proposed structure and adjacent foreshores. Height datum levels for hydrographic surveys should be to the relevant Chart Datum. 2.2.4 Terrestrial surveys Terrestrial surveys should be provided over any land areas that will be incorporated or impacted upon by the project site and should overlap with the hydrographic survey. A

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2.3 GEOTECHNICAL The geotechnical properties and design parameters of seabed materials in the vicinity of a maritime structure should be assessed. These parameters should be used to evaluate foundation capacity, stability and settlement characteristics of the structures and associated works and to determine the response to, and effect on the prevailing natural coastal and estuarine processes. Such processes include tides, current and wave actions and effects of propeller and boat wash.

2.4 ASSESSMENT OF LOADS Maritime structures should be designed to resist the loads applicable to the service performance requirements of the completed facility, the ultimate (survival) loads that the facility may be expected to withstand, as well as loads applicable at the various stages of construction. Wind, wave, tide, current and storm surge and other such natural loads and conditions (including sediment movement, flood debris) should be considered during any investigation of loads applied to, or affecting, the performance of a maritime structure. Wind data should be determined from AS/NZS 1170.2 and/or site-specific anemometer records, where records of adequate duration, to determine an appropriate long-term record, are available. The determination of wave parameters used to derive the design wave height, wave period and wave direction should be assessed using site-specific wave records where records of adequate duration, to determine an appropriate long-term record, are available. If such records are not available, wave heights and periods may be determined from available wind data. Tidal information, including tidal currents, for the site of the works should be determined and appropriate design maximum and minimum tidal planes established. Changes in water levels due to global warming should be considered (see Clause 4.6).

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S E C T I O N 3 D I M E N S I O N A L C R I T E R I A

3.1 STRUCTURE HEIGHTS Deck levels should generally be kept as low as practicable, in keeping with their function to provide access to the waterway and to floating vessels. The minimum height of deck of a wharf or jetty in tidal conditions should be determined as the 1/100 annual exceedance of probability elevated water level, plus a suitable freeboard depending on exposure to waves, wave heights, wind set-up, formation of bars at river entrances and seiche. For wharves and jetties in locations subject to local river flooding or storm surge situations, the design may allow for periodic inundation during such events. Such structures should be able to withstand lateral loads and uplift from elevated water levels including flood effects from the design flood event. Where overtopping of deck structures by waves would result in disproportionate level of damage to the superstructure above main deck level, means to prevent water damage to the property should be incorporated in the design.

3.2 FENDER HEIGHTS Fender structures in tidal waters should extend to at least the height of the sponson or rubbing strake of the highest vessel likely to use the facility, during the design elevated water level, which should be no lower than the highest level that can be predicted to occur under average meteorological conditions and any combination of astronomical conditions (HAT) plus an allowance for storm surge. The fender system should also extend down to a level no lower than the sponson of the smallest craft likely to use the facility, at the lowest level that can be predicted to occur under average meteorological conditions and any combination of astronomical conditions (LAT). Vessel load conditions and motion in response to waves and any other influencing effects should also be considered.

3.3 LAYOUT OF BERTH STRUCTURES The layout of the structures for a berth should be designed to take account of— (a) restraining the vessel against environmental loads (winds, waves and currents) and

interaction effects between passing vessels; (b) providing safe berthing and deberthing in extreme events (storms, floods); (c) allowing safe navigation access to the berth to and from the waterway; (d) minimum intrusion into the navigable waterway; (e) ease of cargo handling; (f) safe personnel and vehicle access; (g) disabled access (where applicable); and (h) minimum impact on the hydrodynamic regime.

NOTE: The operation of some facilities may require that some vessels be removed in the event of a major storm.

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3.4 ACCESS AND SAFETY 3.4.1 Application For maritime structures that may fall outside the provisions of relevant building codes or other regulations, the guidelines in Clause 3.4.2, 3.4.3, 3.4.4 and 3.4.5 should be followed. 3.4.2 Access for operational, inspection, maintenance and servicing personnel Where access to structures is required for operational, inspection and maintenance personnel, the structures should comply with the requirements of AS 1657. Ramps or sloping surfaces should not be located in the tidal zone (where marine growth can make them slippery). Where slopes are required below high water mark, access should be provided by way of a series of horizontally surfaced steps let into the slope, proud of the slope, or cleats fixed to the surface at maximum 300 mm centres. Appropriate non-slip surfacing should be provided. 3.4.3 Access to public transport facilities Where access is required to public transport facilities, structures should comply with the requirements of the Disability Standards for Accessible Public Transport. Gradients of gangways (hinged ramps attached to floating structures, whose gradients varies with the tide) should not exceed 1 in 8 when the tide is at LAT, or steeper than 1 in 12 for more than 20% of the time. 3.4.4 Safety fencing In general, wharf faces and the like are not provided with safety or other fencing to prevent persons or vehicles from falling off the edge of a public access structure. Such fencing would hinder the normal operation of the wharf or maritime facility. Edge kerbs may be considered in areas generally used by wheeled vehicles. Where access to the water or vessels is not required and where a person falling from the structure is likely to fall more than 1.5 m to strike a hard surface or the seabed, a guardrail (handrail) in accordance with AS 1657 should be provided. 3.4.5 Safety ladders Where persons who fall from a wharf or maritime facility would not be able to easily regain the shore, safety ladders should be provided. Such ladders should be of durable material and extend from deck level down to below low water level—bottom rung should be 300 mm below LAT. Such ladders should be located at maximum 60 m intervals. Where safety ladders are used to provide access to craft, suitable buffer rails, at least 250 mm proud of the ladder, should be provided each side to prevent vessels crushing persons on the ladder.

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S E C T I O N 4 D E S I G N R E Q U I R E M E N T S

4.1 AIM The aim of the design of maritime structures covered by this Standard is to provide structures that are stable, have adequate strength against ultimate conditions and remain serviceable while being used for their intended function, and which also satisfy requirements for robustness, economy and ease of construction, and are durable (low maintenance and low repair costs).

4.2 DESIGN REQUIREMENTS 4.2.1 General The design of the structure and its components should take into account, as appropriate, stability, strength, serviceability and durability. The design should be in accordance with the relevant Australian Standards together with any additional recommendations in these guidelines. 4.2.2 Stability The structure and its component members should be designed for static stability under overturning, uplift and sliding and dynamic stability in design conditions as given in Clause 5.12, such that stability loads and other actions exceed the destabilizing loads and other actions. The loads and other actions will need to be combined as given in Clause 5.12. 4.2.3 Strength The structure and its component members should be designed for strength as follows: (a) Determine the appropriate loads and other actions in accordance with Section 5. (b) Combine and factor the loads in accordance with Clause 5.12 to determine the design

loads for strength. (c) Determine the design action effects for the structure and its components for each load

case. (d) Determine the design strength in accordance with the requirements of the appropriate

Australian Standard(s). The effects of fatigue from wind, wave, current and other actions under both normal and storm conditions should be considered. 4.2.4 Serviceability The structure and its component members should be designed for serviceability by controlling or limiting settlement, horizontal displacement and cracking. Under the load combinations for serviceability design detailed in Clause 5.12.4, vertical deflection should be limited in accordance with the requirements of the appropriate materials Standards. Horizontal deflection and acceleration limits for trafficable structures should be limited to a maximum deflection of l/150, where l is the distance between underside of the deck structure to the level of the support in the seabed, and a maximum acceleration of 0.1g. Designers should exercise care at the interface between flexible maritime structures and rigid shoreline structures. Horizontal deflection limits in commercial structures subject to heavy vehicle loadings need to consider dynamic effects of the horizontal vehicle loads (e.g., braking) on the structure. A

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For maritime structures, serviceability conditions are those that may be experienced under normal conditions, and may include for example wave action, which has dynamic effects as well as fatigue effects on those elements constructed from fatigue-prone materials. Typically service conditions would include effects from waves with significant wave heights that occur once or more each year. 4.2.5 Durability The structure and its component members should be designed for durability in accordance with Section 6. 4.2.6 Other relevant design requirements The design should take into account the effects of vessel berthing, scour, flood, cyclic loading, fatigue, temperature effects and any other special performance requirements.

4.3 FLOATING STRUCTURES Floating structures dealt with in this Standard include pontoons used for floating berths (ferry wharves and similar) that are stationary, restrained by piles or permanent moorings and generally in enclosed waters. Floating structures should be designed to maintain a safe freeboard under the most adverse combination of live load and environmental loads including consideration of dynamic effects. The design of floating structures for full live load as well as full environmental loads (storm conditions) is not usually necessary. However live load under serviceability environmental conditions (e.g., once in one-year storm or wave) should be considered in analysis for stability and freeboard. When assessing stability of floating structures under live load, the load cases of full load intensity on the whole deck as well as the case of the full load intensity on part of the deck (e.g., one side of the structure centre-line) should be investigated. The minimum freeboard, ignoring other operation constraints, under the most adverse design loading is 5% of the moulded depth (minimum 50 mm), measured from the top of the flotation unit for rectilinear flotation systems. For horizontal cylindrical flotation systems, freeboard should be at least 25% of the diameter of the cylindrical float, measured from the top of the flotation system. Floating structures should be designed to have watertight sealed compartments to prevent sinking or overturning in the event of a leak in the outer skin. The structure should be capable of maintaining adequate freeboard (under dead load only) in the event of the external skin of any compartment being punctured and filling with water up to the external water level. For large flotation structures (e.g., ferry landings) consideration should be given to allowing access from hatches in the deck.

4.4 BREAKWATERS The function of a breakwater is to reduce wave action either by attenuating the wave as it is transmitted or by reflecting part of the wave energy. Design considerations for breakwaters are that the structure should attenuate wave action without creating adverse conditions and be fit for purpose over their design life.

NOTE: This Standard does not cover the design of rubble mound and floating breakwaters (see Clause 1.1).

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4.5 EFFECTS OF SCOUR AND SILTATION Maritime structures and their component members should be designed to remain stable and of sufficient strength and not be overloaded in the event of temporary or permanent changes in the level of the seabed due to scour or silting. Wharves and jetties in river estuaries should be analysed with appropriate allowance for velocity-induced scour, which may be exacerbated at the peak of a flood event. Structures in coastal areas subject to littoral drift should be analysed with allowances for erosion of the seabed in down-drift areas, and build-up of sediment in up-drift areas. Wharves used by vessels should be designed to allow for this additional scour effect to the materials beneath the wharf from propeller wash or bow or stern thrusters.

4.6 SEA LEVEL RISE (global warming) Maritime facilities should be designed to cater for increase in water level due to promulgated sea level rises caused by global warming. The amount of sea level rise to be considered depends on the design life of the structure. The allowance for sea level rise does not necessarily include the construction of the deck of the facility at a higher level, although in some cases this may be prudent. Allowance for sea level rise may include options to raise the heights of restraining piles on floating structures at a later time, or installing substructure of adequate strength to permit future topping slabs etc. The allowance for future sea level rise is provided in Table 4.1.

TABLE 4.1 ALLOWANCE FOR SEA LEVEL RISE

Design life Sea level rise m

25 years 0.1 50 years 0.2

100 years 0.4 NOTE: Based on the mid-scenario from the International Panel on Climate Control (2001). These values are updated by IPCC from time to time.

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S E C T I O N 5 D E S I G N A C T I O N S

5.1 GENERAL The design for ultimate strength, serviceability, stability and other relevant limit states should take into account the appropriate design actions arising from those given in AS/NZS 1170, and other actions applicable to maritime structures, as follows: (a) Permanent actions (dead loads) (see Clause 5.2). (b) Imposed actions (live loads) (see Clause 5.3). (c) Wind actions (see Clause 5.4). (d) Current and debris actions. (e) Hydrostatic actions. (f) Wave actions. (g) Thermal, shrinkage and other movement induced actions. (h) Construction and maintenance actions. (i) Lateral earth actions on waterfront structures (seawalls). (j) Propeller wash. (k) Earthquake actions.

5.2 PERMANENT ACTIONS (DEAD LOADS) Dead loads include the self-weight of all structures, all deck wearing surfaces, long-term loads such as cargo storage facilities, superstructures, and mooring fittings (bollards, quick-release hooks, etc.). Piles and other elements immersed in the sea should include the influence of marine growth.

5.3 IMPOSED ACTIONS (LIVE LOADS) 5.3.1 Wharf deck loads Wharf surfaces should have a specified loading classification that will govern the design of all elements of the structure, including deck, beams, headstocks and piles. Distributed loads should be applied over the whole of the deck between kerbs, or inside handrails, etc. Loads should be applied to a single span, or all spans, or alternate spans to produce the worst design effect. Concentrated loads should be applied at a critical location in one span in lieu of a distributed load. The design loads and classifications shown in Table 5.1 should apply as appropriate for the facility, or as specified by the owner of the facility particularly for large port projects. For wharf decks that handle containers, the design of the wharf structure should be checked for the loads applicable for the particular arrangement of containers and container handling equipment as indicated in Appendix A, in addition to the loads given in Table 5.1. The loads indicated in Table 5.1 and Appendix A are service loads. These loads need to be factored to obtain ultimate limit state (strength) design loadings. Structures should be designed for directly related horizontal live load actions such as braking loads from vehicles, slewing/luffing loads from cranes.

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Any freestanding maritime structure (jetty, dolphin, etc.) should be capable of withstanding a minimum horizontal load (Flat), applied at deck level, of at least 2.5% of the maximum permanent and imposed vertical actions. This horizontal action should be applied in the lateral and longitudinal directions (not simultaneously) and should not be superimposed on any other applied horizontal actions.

TABLE 5.1 MARITIME STRUCTURES —DECK LOAD CLASSIFICATIONS

Class Uniformly distributed

load (Q) (see Note 1)

Concentrated load

(area, mm) s = spacing, m

(see Note 2)

Anticipated load conditions Application

5 5 kPa 20 kN (150 × 150)

s = 1.8

Pedestrian crowd load. Light motor vehicles up to 3 t tare

Private and public boardwalks. Passenger jetties

10 10 kPa 45 kN (300 × 150)

s = 1.8

Small emergency vehicles Public boardwalks and promenades with access for emergency vehicle and service vehicles

15 15 kPa 200 kN (400 × 700)

s = 4.0

Bridge design code (W7, W8, A160, T44 loading) Small mobile crane up to 20 t SWL

Light-duty wharf and jetty for fishing industry, charter boat industry, ferry wharves, light commercial activities

25 25 kPa 500 kN (700 × 700)

s = 5.0

Bridge design code (SM1600 heavy platform loading) Mobile crane 50 t SWL

Secondary port general cargo wharf

40 40 kPa 1000 kN (1000 × 1000)

s = 7.0

Container forklift and other machinery for 40 ft containers Mobile crane 100 t SWL

General cargo wharf or container wharf (For containers stacked 2 high ship-side, see Note 3 & Appendix A)

50 50 kPa 1500 kN (1000 × 1000)

s = 8.0

Container forklift, reach stacker and other machinery for largest containers Mobile crane 150 t SWL

Primary port, international gateway container terminal (For containers stacked 2 high ship-side, see Note 3 & Appendix A)

60 60 kPa 2000 kN (1000 × 1000)

s = 9.0

Mobile crane to 200 t SWL Heavy-duty maintenance wharf

NOTES: 1 The above loads do not include any component for dynamic effect (rolling ‘impact’, or heavy landings of

cargo loads). The impact and dynamic load factors should be applied as appropriate. 2 s = spacing (metres) in any direction between concentrated loads, or between concentrated loads and the

edge of uniformly distributed loads. Concentrated loads and uniformly distributed loads identified in the above table should not be superimposed.

3 The storage of containers on the wharf deck at ship-side is for temporary storage of containers while accessing containers within the vessel. Loadings in container yards are not covered by these guidelines, as such loads are terminal specific.

5.3.2 Vessel berthing and other imposed loads 5.3.2.1 General The structure should be designed to withstand loads associated with the berthing of vessels within the design vessel range appropriate for its use. A

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The energy of berthing vessels may be absorbed in one or a combination of the following ways: (a) In deflection of the vessel hull (usually only for small vessels <500 t). (b) In deflection of the berthing structure, where it is specifically designed to flex under

loading. (c) Through an energy-absorbing berthing fender system mounted on a wharf or dolphin

structure. (d) Through the action of a vessel forcing water between the vessel and the shore. 5.3.2.2 Energy absorption through vessel hull In the case of small vessels up to 500 t displacement, the berthing energy may be considered to be absorbed through deflection of the hull of a vessel as well as deflection of the berthing structure or berthing fender system. For such vessels, hull deflections of up to 75 mm for quarter-point to mid-point berthing may be considered. (For end-impacts, no deflection should be considered.) 5.3.2.3 Energy absorbed through deflection of a berthing structure Some berthing structures may be designed to absorb berthing energy by deflection of the structure itself. The energy absorbed by the flexible structure is the integral of the reaction load from the structure over the displacement of the structure (at the point of contact with the vessel), to bring the vessel to a standstill. The loading in a flexible berthing structure may be reduced by providing an energy absorbing ‘soft’ fender system on the structure (see Clause 5.3.2.5), in which case the berthing energy imparted to the structure will be reduced by the capacity of this fender system. Design of flexible berthing structures, such as flexible dolphins and berthing beams, should allow for absorption of the maximum (abnormal) berthing energy in elastic deflection of the structure and foundations, to provide full restitution after loading. (Accidental overload beyond abnormal berthing may result in permanent displacement of the structure). 5.3.2.4 Energy absorbing fender systems An energy absorbing fender system will usually comprise an elastomeric energy absorbing unit, and associated contact faces, mounted on the front of a rigid (or semi-rigid) wharf or dolphin structure, such that the whole of the berthing energy is absorbed by the fender system. The structure should sustain the reaction loads from the fender system mountings, in three axes of translation and in rotation. 5.3.2.5 Determination of berthing energy and loads Where more accurate data is not available, berthing energy should be determined in accordance with Appendix B. The berthing energy is dissipated and results in loads on the berthing structure that are either reaction loads induced during deflection of a flexible structure itself, or reactions from the ‘soft’ fender system. Reactions on a berthing fender system may be from any or all of— (a) elastomeric (‘soft’) fender unit; (b) fender system restraint and reaction chains; (c) fender piles; and/or

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(d) loads may be normal to wharf (direct impact), as well as friction loads that are longitudinal and vertical.

The fender system should be designed for the full range of design vessels for the facility, to accommodate the characteristics of all vessels from smallest to largest. Where possible, particularly with passenger vessels, care should be exercised to provide a soft fendering system for small craft, while still providing adequate capacity to absorb energy from the largest design vessel. The berthing energy calculated in accordance with Appendix B is the energy of the vessel approaching perpendicular to the wharf face. This energy is based on normal operations, and thus represents the serviceability condition. An abnormal berthing condition should also be considered in the fender design, arising through mishandling, malfunction or exceptionally adverse wind or current or a combination of these. In abnormal berthing conditions, the energy capacity of a fender system should be capable of absorbing 1.25–2 times (or greater) the calculated normal berthing energy (refer to PIANC Guidelines). Thus a fender unit that is to be selected should be able to accommodate— (i) normal berthing energy for serviceability condition up to the rated capacity of the

fender unit; and (ii) abnormal berthing energy up to the maximum capacity of the fender unit. The corresponding fender unit reaction load should be applied as a lateral load into the berthing structure. The ultimate strength design of the fender support structures should then consider the greater load of— (A) the rated fender reaction load, with appropriate Limit State load factors applied; and /

or (B) the abnormal berthing case reaction (maximum fender reaction), considered as an

ultimate Limit State load condition. Shear and tension loads during fender impacts should be calculated for a range of possible berthing events, which should be applied to the fender support structure. Shear loads are due to longitudinal and/or vertical friction on the face of the fender during vessel impacts. These are transferred into the berthing structure through the body of the fender unit and/or restraint or reaction chains. Where these loads are substantial, they may be reduced with the use of low friction facing material on the fender frontal panel. For fender impacts exceeding the ultimate strength condition, the designer should consider the ramifications of failure of the berthing structure. For strategic installations, such as major single use facilities and oil or gas loading/unloading facilities, etc., consideration should be given to separation of the berthing structure from the wharf facility so that accidental impact damage to the berthing structure does not necessarily prevent the continued use of the facility. 5.3.3 Mooring loads Mooring loads are loads generally applied to structures by mooring lines or ropes. Such loads include wind and current loads on moored vessels, transferred to the wharf, jetty or dolphin structures by the mooring lines. Mooring loads may also include loads resulting from vessels manoeuvring to or from the berth using engines and rudders while moored to bollards. Loads applied to mooring bollards or similar fittings may be calculated using wind and current loads on the moored vessel. To cater for mooring loads from manoeuvring vessels bollard loads indicated in Appendix C should be considered.

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There may be site-specific practices where large vessels may be directed to leave the berth during periods of high wind speeds. These circumstances should be identified and appropriate design wind speeds determined.

5.4 WIND ACTIONS 5.4.1 Determination of wind actions Wind actions on wharves and wharf buildings and on stored materials or vehicles should be designed in accordance with AS/NZS 1170.2. Wind actions on vessels and floating structures may be designed using a wind pressure based on a 30 s gust rather than basic wind speeds due to 3 s gusts. This is because floating structures have a delayed response to wind loads. The 30–second wind speed may be taken as 0.87 times the relevant basic wind speed as specified in AS/NZS 1170.2. Terrain category 2 (in AS/NZS 1170.2) is generally appropriate for wind over exposed fetches, due to surface roughness of the water at design wind speeds. 5.4.2 Wind actions on a vessel or structure Wind pressure on a vessel or structure should be calculated from the following equation:

2z 0006.0 Vq = . . . 5.4.2(1)

where qz = wind pressure, in kilopascals V = design wind speed, in metres per second = Vu for ultimate limit state = Vs for serviceability limit state

Wind loads on a vessel or structure should be calculated from the following equation: zDD AqCwF = . . . 5.4.2(2)

where FD = load in direction of wind, in kilonewtons CwD = coefficient of wind drag (see Table 5.2) A = projected area of element, in square metres qz = wind pressure, determined from Equation 5.4.2(1), in kilopascals

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TABLE 5.2 TYPICAL WIND DRAG COEFFICIENTS

Vessel or structure Coefficient of drag (CwD) Vessels (up to 10 000 t) Tubular piles Rectangular members

1.1 to 1.2 1.2 2.0

NOTE: For vessels in excess of 10 000 t refer to BS 6349 for calculation of wind loads.

5.5 CURRENT ACTIONS 5.5.1 Design current The design strength of maritime structures should allow for the combined effects of tidal and/or river/estuarine flood currents. 5.5.2 Calculation For structures and vessels up to 10 000 t subject to currents, the loads should be calculated from the following equation:

32D2

1s 10−×= ρAvCsF . . . 5.5.2

where Fs = current load, in kilonewtons CsD = stream flow drag coefficient (see Table 5.3) v = current velocity, in metres per second A = projected area of element, in square metres ρ =

= 1026 kg/m3 for sea water 1000 kg/m3 for freshwater

TABLE 5.3 STREAM FLOW DRAG COEFFICIENTS

Structure Drag coefficient (CsD)

Circular piles—Smooth 0.70 Circular piles—Rough 1.04 Square piles or beams with sharp corners 2.20 Square piles or beams with corners rounded 0.70–1.0 Piles—Heavy marine growth 1.5–1.8 Debris mat 2.001 Vessels bow to current 0.30 Vessels beam to current 0.40 NOTES: 1 For more accurate assessment of the drag coefficient for the debris mat

refer to AS 5100.2. 2 For vessels in excess of 10 000 t refer to BS 6349 for stream drag loads.

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5.6 DEBRIS ACTIONS For structures where a debris mat could form against the structure (most river estuarine situations), the structure should be designed for a mat of thickness not less than 1.2 m, and not greater than 3 m. The load exerted by the debris mat may be calculated using Equation 5.5.2, where the gross area of the mat (A) is measured normal to the direction of the stream flow. All structures subject to flood debris should be designed for a minimum load of 10 kN per metre of structure. This applies to both fixed and floating structures.

5.7 NEGATIVE LIFT DUE TO CURRENTS For floating structures in waterways subject to flood currents, a phenomenon known as negative lift should be considered. This phenomenon occurs as a result of currents passing under the floating structure and causing downward load on the leading edge of the structure. The negative lift is proportional to the flow velocity squared, and can result in submersion of the leading edge of floating structures at moderate velocities, sometimes resulting in overturning of the structure. Negative lift phenomena should be examined where current velocities exceed 0.5 m/s.

5.8 HYDROSTATIC ACTIONS Hydrostatic loads on structures result in lateral pressures and uplift on walls and floor slabs of maritime structures. In considering hydrostatic loads, the highest design water level (flood level or storm elevated sea level) should be used. 5.8.1 Uplift stability Uplift stability of submerged or buried structures should be considered for the minimum weight for the structure and should be taken as the most severe of the following: (a) Structure empty In maritime conditions, use of pressure relief systems cannot be

relied on for preventing uplift. Ground anchors (passive or prestressed) may be included in stability calculations.

(b) External water level is highest of— (i) maximum design water level plus half-wave height or more, as appropriate; or (ii) equal to top of structure, above which rising water levels will cause the

structure to either submerge or fill. 5.8.2 Tidal lag Hydrostatic effects on seawalls and other waterfront structures should consider tidal lag. Tidal lag occurs when the level of ground water behind the wall lags behind the water level in front of the wall, due to the slower drainage characteristics of the wall backfill compared to tide level fluctuations in front of the wall. In the absence of more detailed site-specific analysis on soil and wall permeability, the minimum water differential to be considered due to tidal fluctuations should be the larger of— (a) 1/3 of the spring tidal range; or (b) 500 mm.

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5.8.3 Ground water Where rainwater run-off or other significant surface or subsurface flows could drain into the backfill of a seawall or other waterfront structures at a higher flow rate than could be expected to drain out through the subsoil or back-wall drainage system, the design of the seawall or maritime structure should allow for a hydrostatic pressure based on a water table at the top of the wall or structure backfill. 5.8.4 Wave backpressure Backpressure on seawalls or other waterfront structures may result from the effects of waves on the wall penetrating the face of the wall through joints or cracks. Consideration should be given to— (a) waves running up and overtopping the structure, resulting in a high water table behind

the structure (up to the level of the top of the seawall or structure); (b) waves penetrating the fabric of the seawall (through cracks, joints, etc.) which causes

a locally high water table behind the wall, which may co-exist with the passage of a wave trough in front of the seawall, resulting in high local differential hydrostatic pressures on the structure. (Such localized differential pressures have resulted in failures in seawalls.)

5.9 WAVE ACTIONS 5.9.1 General Waves can be classified as three types, with corresponding significant wave heights (Hs) and wave periods (Ts). Wave classifications are ‘swell-waves’, ‘wind-waves’ or ‘vessel-wash’. Design storm events are generally described by the ‘significant wave height’ associated with the peak of the storm event. 5.9.2 Design wave heights The design strength of maritime structures should allow for the highest wave likely to occur on the structure over the selected design life and an annual probability of exceedance based on the function category of the facility. The annual probability of exceedance of significant wave heights, for structures of various design lives and function categories, are shown in Table 5.4.

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TABLE 5.4 ANNUAL PROBABILITY OF EXCEEDANCE OF DESIGN WAVE EVENTS

Design working life (years)

Function category Category description 5 or less

(temporary works)

25 (small craft

facilities)

50 (normal

maritime structures)

100 or more (special

structures/ residential

developments)

1 Structures presenting a low degree of hazard to life or

property 1/20 1/50 1/200 1/500

2 Normal structures 1/50 1/200 1/500 1/1000

3 High property value or high risk to people 1/100 1/500 1/1000 1/2000

NOTE: The design water levels used in combination with waves determined from Table 5.4 should be taken as not below mean high water springs. The design wave for structures should be equivalent to H1, taken to be the average of the highest 1% of all waves in the design storm event. The design wave conditions may be determined by more specific modelling or, for structures where the wave loads are a small part of the design loads, the following simplifications may be used: H1 should be determined by applying a factor to the significant wave height for the design storm, as follows:

H1 = fHs . . . 5.9.2For fully enclosed waters with maximum fetch lengths less than 10 km, f may be taken as 1.50 (short narrow fetch) to 1.70 (longer wider fetch). For open waters, where storm waves are likely to be superimposed on swells, f should be taken as 1.70 (e.g., normally calm waters—tropical Australian coastlines) to 2.0 (e.g., high energy waters—southern Australian coastlines). Where the structures are close to reflective seawalls, account should be taken of higher waves resulting from reflected waves interacting with incident waves. 5.9.3 Design lateral wave loads The design of elements of structures should include design for the lateral loads of the waves impacting the structure, using recognized wave load formulae, or from hydraulic modelling. 5.9.4 Wave uplift loads Structures where waves can travel under the soffit of the structure (jetty deck slabs under extreme wave conditions, low level landings, drainage out-falls, etc.) are subject to dynamic wave uplift loads. The uplift load may be approximated as the head of water corresponding to the wave crest as if the structure were not present, factored by 2.0. This load may act upwards or downwards as the wave passes. In addition to this slowly varying dynamic pressure, structures containing re-entrant corners (e.g., where slab soffit meets down-stand beam) can experience very high wave impact loads, with pressures several times the slowly varying pressure. The impact loads are of very short duration, and extend over a limited area around the re-entrant corners.

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Structures where these loads are exerted can often accommodate such loads if other dynamic wave loads are adequately catered for and if the deck is structurally continuous over a larger area than the area exposed to impact pressures. Where these impact loads are likely to occur, designs should consider the details for resisting uplift loads (holding down bolts, reinforcement in the region of anchors, etc.) or the provision of pressure-relief systems or vents. Where possible, these high impact wave loads should be avoided by eliminating re-entrant corners (e.g., use of flat plate concrete slabs on tubular piles) or by providing pressure-relief openings.

5.10 CONSTRUCTION AND MAINTENANCE ACTIONS Construction and maintenance actions on maritime facilities should take into consideration the probable use of cranes and other heavy loads required to construct and maintain maritime structures. Sometimes construction and maintenance actions on over-water structures may exceed the service loads of the structure.

5.11 LATERAL EARTH ACTIONS Lateral earth loads on waterfront structures and seawalls should be obtained by consideration of the soil parameters for the in situ soil and/or backfill against the structure. Earth-retaining structures should be designed for a minimum surcharge load equal to the uniformly distributed load used for the design of the adjacent deck. For seawalls with no associated wharf deck, the minimum surcharge should be 5.0 kPa. Where the area behind seawalls is subject to vehicle or other heavy loads, the surcharge should be increased in accordance with Table 5.1. Use of relieving slabs may be required to improve the stability of the earth-retaining structures. Consideration should be given to the effects of lateral water pressure in conjunction with lateral earth loads, in accordance with Clause 5.8.

5.12 COMBINATIONS OF ACTIONS 5.12.1 General Unless otherwise specified, a structure and its components should be designed to resist the loads applicable to the in-service performance requirements of the structure, ultimate loads during storm or flood conditions, as well as loads applicable to the intermediate stages of construction. Care should be exercised in defining combinations of actions to ensure the proper design action effect for actions that— (a) do not act simultaneously; (b) act simultaneously, but not superimposed; or (c) act simultaneously and are superimposed. Combinations specified in AS/NZS 1170 should be considered. In addition, combinations of actions relating to maritime facilities should be considered. 5.12.2 Stability The basic combinations used in checking stability should be as detailed in AS/NZS 1170.0, and as appropriate, the following: (a) For combinations that produce net stabilising effects (Ed,stb):

Ed,stb = [0.9G] permanent action only

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(b) For combinations that produce net destabilising effects (Ed,dst): (i) Ed,dst = [1.2G, Su, Fenv] permanent action and actions given in

Clause 5.12.4 and/or Clause 5.12.5 (ii) Ed,dst = [1.2G, Q, Su, Fenv] permanent and imposed actions, and actions

given in Clause 5.12.4 and/or Clause 5.12.5 5.12.3 Strength The basic combinations used in checking strength should be as detailed in AS/NZS 1170.0, plus, as appropriate, the following: (a) Ed = [1.2G, Su, Fenv] permanent actions and actions given in Clause 5.12.4

and/or Clause 5.12.5 (b) Ed = [1.2G, 0.6Q, Su, Fenv] permanent and imposed actions and actions given in

Clause 5.12.4 and/or Clause 5.12.5 (c) Ed = [0.9G, Su, Fenv] permanent actions and actions given in Clause 5.12.4

and/or Clause 5.12.5 5.12.4 Combinations for berthing and stream loads, water pressure, ground water and earth pressure The basic combinations should be modified for berthing and stream loads, water pressure, ground water and earth pressures. Appropriate combinations may include one or a number of the following factored values: (a) Su = 1.5Fb for normal berthing loads (b) Su = 1.0Fb.u for abnormal berthing loads (c) Su = 1.5Fm for mooring loads (d) Su = 1.5Flat for the minimum horizontal load (see Clause 5.3.1) (e) For submerged or partially submerged structures, where the design water height is at

the top of the structure and cannot be exceeded: Su = 1.2Flp for static water pressure that is measured to the top of

the structure (see Clause 5.8.1(b)) Su = 1.5Flp where the design water level could be exceeded (f) Su = 1.5Fe for earth pressures (g) Su = 1.5Fgw for ground water (h) Su = 1.5Fs for ultimate stream flood flow and debris 5.12.5 Combinations of wind and wave loads The basic combinations should be modified for environmental loads due to wind and waves. Appropriate combinations may include one or a number of the following ultimate values: (a) Fenv = Wu ultimate wind load (b) Fenv = Fwave.u ultimate wave load (c) Fenv = Wu ,0.7Fwave.u, 1.5Fs ultimate wind and wave (d) Fenv = 0.7Wu, Fwave.u ultimate wave and wind

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5.12.6 Serviceability Combinations for the serviceability limit states should be those appropriate for the serviceability condition being considered. Appropriate combinations may include one or a number of the following using the short-term and long-term values as appropriate: (a) G (b) Q (c) Es (d) Fb (e) Fm (f) Flp (g) Fs (h) Fe (i) Fgw (j) Ws (k) Fwave.s (l) Serviceability values of other actions, as appropriate. 5.12.7 Cyclic actions Structures that are subject to continuous wave action should be designed to cater for cyclic loadings. The magnitude of the repeated loadings when designing such structures, or elements of structures, for fatigue performance should be determined from in-service cyclic actions. That is, structures should be adequate to resist the ultimate wave loads as well as substantially smaller waves that result in constant cyclic loads leading to fatigue conditions.

NOTE: Structures in a waterway where waves constantly occur, with a typical period of 2 s to 4 s, will experience 106 cycles per annum.

5.13 PROPELLER WASH The submerged elements of structures that are subject to propeller wash from passing vessels, in particular tugs, and from thrusters should be designed to cater for such loads. Where tugs are likely to be operating routinely for assistance in manoeuvring large vessels, the siting of small craft facilities in such areas should be planned carefully, as propeller wash from tugs can affect the safe operation of small craft. (Propeller wash current speeds may be up to 8 m per second, adjacent to a tug vessel.)

5.14 EARTHQUAKE ACTIONS 5.14.1 General Design of structures for earthquake actions (Eu) have to ensure that adequate capacity exists for overall stability and member strengths and that the detailing of the structure will be sufficient for the expected movements of the structure. Design actions to be resisted are defined by AS 1170.4. Nevertheless, in considering the application of AS 1170.4 it should be recognized that the Standard is particularly directed to the design of buildings and similar structures that are often significantly different to maritime applications.

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5.14.2 Maritime structures Structures subjected to earthquake conditions often sustain less damage if the structure has a higher degree of shape regularity, simple load paths with multiple redundancies and simple connections. These properties should be considered at the time of definition of the structural systems and carried through the design where at all possible. Also of significant effect on maritime structures designed to withstand an earthquake are the following: (a) Structural ductility Often maritime structural design has elements with significant

variation in member ductility, e.g., limited ductility concrete deck supported on ductile steel piles. The elements of lesser ductility need to be considered to ensure the displacements that would be expected to occur in the elements of higher ductility do not adversely affect the structure. The structural ductility factor(s) selected needs to be able to be reliably achieved by the structure. If suitable for the application, ductile response may be achieved by utilizing ‘fuse’ elements in the structure, designed to absorb the earthquake energy while protecting the significant structure. If a fuse element is used, it should be easily accessible and, if necessary, replaceable/repairable.

(b) Soil conditions The soil conditions in the surface layers generally define the site’s dynamic stiffness and period regardless of the depth of actual founding stratum. Special consideration is, however, required for the possibly more adverse conditions where raking piles or squat members are founded on a stiff stratum, regardless of the depth. The possibility of liquefaction, especially of sand layers, should be considered. If liquefaction is determined to occur, then the effect of liquefaction on the structural analysis has to be included.

(c) Response of adjacent structures and supported structures Consideration of the earthquake response of adjacent structures is required to ensure that conflict in responses does not result in the adverse contact, or loss in contact, between the structures, e.g., impact of wharf segments or loss of bridging elements to dolphins. Adverse interactions between the structure and any supported structures (e.g., cranes, buildings, etc.) should be considered in the analysis (e.g., crane stability).

(d) Structural importance factors Many significant maritime structures perform a post-disaster function or could be considered economically significant structures due to loss of function or cost of reinstatement. Elements of a structure of high importance, which are not required for the general function of the structure, may be assigned a lower structural importance factor, provided the elements will not compromise the remaining structure by its possible failure under a lesser effective design event.

(e) Stability of reclamation and revetments The maritime structure being considered may be adversely affected by the failure of adjacent slopes due to an earthquake. This slope stability effect may or may not occur during the peak earthquake accelerations. Specialist advice is recommended.

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S E C T I O N 6 D U R A B I L I T Y

6.1 GENERAL Maritime structures are generally sited in very aggressive environments for normal structural materials, and the design of maritime structures should include consideration of the requirements to withstand the aggressive environment while the structure remains serviceable. The effect of extreme events on the structure’s durability should also be considered. For example, the effect on concrete structures, which may be heavily stressed and cracked in an extreme event early in the life of the structure, should be considered, where such cracking may then lead to accelerated corrosion of steel reinforcement.

6.2 DESIGN LIFE 6.2.1 General Design life is defined as the period for which a structure or a structural element remains fit for use for its intended purpose with appropriate maintenance. The design life of maritime structures will depend on the type of facility and its intended function (see Table 6.1). This design life will depend on the owner’s requirements. As well as determining loads for a facility, it is necessary to decide on a realistic design life for the structure. This design life should be based on consideration of capital and maintenance expenditure. Durability is to be realized either by a maintenance program, or, in those cases when maintenance cannot (or is not expected to) be carried out, by design such that deterioration will not lead to failure. In the latter case the initial capital cost is expected to be high. The designer should determine an appropriate maintenance regime consistent with the adopted design and materials that will achieve the design life. Particular care should be taken when considering design life and maintenance regimes for inaccessible members. Sections or components of the structure that have limited access or are inaccessible after construction should have a design life (with no maintenance) equal to the design life of the structure. At the end of the design life, the structure should have adequate strength to resist ultimate loads and be serviceable, but may have reached a stage where further deterioration will result in inadequate structural capacity.

TABLE 6.1 DESIGN LIFE OF STRUCTURES

Facility category Type of facility Design life

(years) 1 Temporary works 5 or less 2 Small craft facility 25 3 Normal commercial structure 50 4 Special structure/residential 100

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6.2.2 Material considerations 6.2.2.1 General The choice of materials to achieve the design life of a maritime structure should reflect the required design life and the agreed maintenance regime. Issues that should be considered when selecting concrete, steel or timber are detailed in Clauses 6.2.2.1, 6.2.2.2 and 6.2.2.3. Whilst this Section deals with the use of concrete, steel and timber, it does not preclude the use of other materials. 6.2.2.2 Concrete The following items should be considered when selecting concrete as a material in the design of a maritime structure: (a) Concrete deterioration is usually a result of corrosion of reinforcing steel due to

chloride ingress. (b) Reinforced concrete may not be a ‘lifetime’ maintenance-free material. Reinforced

concrete structures require regular condition inspection and maintenance of deteriorated sections. Recent history has shown some maritime concrete structures experiencing significant premature deterioration as a result of an inappropriate selection of materials for the required design life.

(c) Improved performance of concrete structures will be achieved by a combination of the following: (i) Limiting design stresses in reinforcing steel. (ii) Appropriate selection of member sizes, shapes and detail. (iii) Improved performance concrete. (iv) Improved performance reinforcements. (v) Closely controlled construction methods.

(d) Repairs may require the removal and replacement of deteriorated concrete and reinforcement. Considerations include the ability to— (i) access the member with working scaffold for inspection and repair; (ii) remove and contain waste materials during repair works; and (iii) apply and maintain an adequate curing regime to the repair works.

6.2.2.3 Steel The following items should be considered when selecting steel as a material in the design of a maritime structure: (a) Steel deterioration (corrosion) results from the breakdown of the protective coating or

other protective system. (b) Paint coatings provide a service life of approximately 20 years, before

repair/recoating is necessary. (c) The maintenance strategy may allow the reinstatement of a protective coating/system

before corrosion of steel begins, or for the deterioration of the steel member until replacement of the protective coating/system and/or the member is required. Considerations include the ability to— (i) access the member with working scaffold for inspection and repair; (ii) remove and contain waste materials during repair works; and (iii) prepare and apply protective coatings in situ to achieve required standard. Accessed b

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(d) The preparation and recoating of steel in the marine environment is difficult and standards reached in the manufacturing process are not usually achievable in this environment.

6.2.2.4 Timber The following items should be considered when selecting timber as a material in the design of a maritime structure: (a) Individual timber members are relatively small, forming an assembly of members

within a structure. Members can usually be replaced easily within a structure to maintain the structural capacity, without significant interruption to service operations.

(b) The service life of timber members will vary significantly depending on application, timber quality (grade), species natural durability and preservative treatment. The following times to first maintenance can be expected: (i) Timber piles exposed to marine organisms ......................................5–10 years. (ii) Timber piles not exposed to marine organisms ..............................10–30 years. (iii) Timber decking exposed to weathering..........................................10–25 years.

(c) The deterioration of timber is usually by mechanical degradation, rot or attack by living organisms (decay fungi, termites, marine borers).

(d) Where not in a continuously wet environment, natural shrinkage due to drying timber will result in the need to tighten bolted connections during early years of the structure’s life.

(e) A maintenance strategy may allow for regular and frequent replacement of timber members throughout the design life, as individual components deteriorate. Considerations include— (i) the availability of skilled carpenters, able to maintain the works over the

structure’s design life; (ii) the future availability of suitable timber species and member sizes; (iii) the commitment of resources to regular inspection and maintenance of

structures; and (iv) the detailing and accessibility of bolted connections for ease of replacement

during maintenance works. 6.2.3 Maintenance All maritime structures deteriorate over time. Early maintenance is generally recommended to prevent more significant damage. Whilst a structure may have a prescribed design life of 25, 50 or 100 years, local marine environments, operational conditions, and other factors will lead to maintenance requirements. Regular (annual or otherwise) inspection of the structure will permit early detection allowing the implementation of economic maintenance measures. Maintenance will then be determined by the inspection results. A typical maintenance program will include— (a) regular inspections; (b) a program of routine minor maintenance; and (c) a program of major maintenance.

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6.3 CONCRETE 6.3.1 General The predominant cause of deterioration of concrete maritime structures is corrosion of reinforcement and prestressing tendons. This is particularly evident in the splash zone. Design of concrete maritime structures should focus on minimising the causes of premature corrosion of steel reinforcement as the repair of this deterioration may require major reconstruction of the affected elements and possibly pose restrictions on the use of the facility during repair/reconstruction. There has been a trend for designers to specify high-strength concrete, that is, concrete with a characteristic compressive strength above 50 MPa, to reduce permeability and thus improve the durability of maritime structures, where a lower strength would satisfy design strength requirements. However, unless proper construction techniques are adopted, particularly in compaction and curing, other problems including plastic shrinkage and thermal cracking may compromise durability. In addition, economical and slender structures, which can result from using the higher strength concretes, can lead to structures that are more highly stressed in flexure and are susceptible to chloride penetration through the wider crack widths. Each concrete structure needs to be assessed individually to determine appropriate requirements for it to be durable. Consideration should be given to the particular environment, the type and use of the structure, the quality of the in situ concrete, the detailing of the structure and the proposed maintenance regime. The requirements for individual elements within a given structure will vary, as will the requirements for different structures. The general advice given in this Standard regarding certain aspects of concrete maritime structures is offered to facilitate this individual assessment and should not be assumed to negate the necessity for carrying it out. The objective of the design for durable concrete structures is to reduce the opportunity for chlorides from sea water to cause the reinforcement to corrode. The designer should, at the outset, review all the alternative strategies available. For example, the use of plain concrete members, the use of stainless steel reinforcement, the encapsulation of prestressing tendons in watertight plastic conduits, and the use of protective coatings to concrete members should be examined. 6.3.2 Structural design Structural concrete should comply with the design and performance requirements of AS 3600, together with any applicable recommendations made by these guidelines. Engineering judgement will be required in the use of AS 3600, where stainless steel reinforcement is adopted, as AS/NZS 4671 does not encompass this material type. 6.3.3 Structural concrete The following is recommended for structural concrete in a maritime structure: (a) Specifying special-class concrete. (The designer to specify particular requirements for

the concrete, e.g., binder type and proportions as well as water-binder ratio, and normal criteria such as strength).

(b) A minimum characteristic compressive strength (f′c) of 40 MPa.

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(c) General purpose Portland cement alone as the binder, or a blended cement in accordance with AS 3972. NOTES: 1 It has been shown that for certain concrete mixes blended cements may improve the

resistance to chloride penetration as well as slowing the rate of hydration of the binder, reducing the potential for thermal cracking.

2 When using blended cements particular attention needs to be paid to placement, finishing and curing, to achieve the required strength and performance of concrete.

(d) Cementitious content (Portland and blended cements) should be not less than 400 kg/m3.

(e) For exposure classes C1 and C2, a drying shrinkage at 56 days not greater than 600 × 10−6 mm/mm, determined in accordance with AS 1012.13.

(f) A maximum water to binder material ratio not more than 0.40. Super-plasticizers should be used, to reduce water content whilst maintaining adequate workability.

(g) Concrete should be placed in watertight forms, thoroughly compacted and protected from excessive temperature and wind evaporation.

(h) All maritime concrete structures should be water-cured for at least 7 days and preferably 14 days under ambient conditions. Curing should commence immediately after finishing horizontal surfaces. If forms are stripped within 7 days, then supplementary water curing should take place to 7 days. NOTE: The use of chemical curing compounds is not recommended on maritime concrete. The use of penetrating chemicals for chloride inhibitors, such as silanes, siloxanes or other surface coatings, precludes the use of chemical curing compounds on maritime concrete.

6.3.4 Requirements for reinforcement Carbon steel reinforcement should comply with AS/NZS 4671 and be used and fabricated in accordance with AS 3600 and the following: (a) The total surface area of carbon steel reinforcement in maritime structures should be

minimized to reduce the opportunity for corrosion by chloride-contaminated concrete. A smaller number of large diameter bars is preferable to a larger number of small bars, provided that the crack control provisions of AS 3600 for bar diameter and bar spacings, as appropriate, are satisfied. Minimum size bars for reinforcement should be in accordance with Table 6.2, and be 16 mm diameter in slabs and 20 mm (preferably 24 mm) in beams. Small bars used for ties and ligatures should be not less than 10 mm diameter.

TABLE 6.2 MINIMUM BAR DIAMETERS IN MARITIME CONCRETE STRUCTURES

(CARBON STEEL) Bar location Minimum diameter

Slabs 16 mm Beams, up to 500 mm deep 20 mm (24 mm preferred) Beams, over 500 mm deep 24 mm (28 mm preferred)

Ties and ligatures 10 mm (12 mm preferred)

(b) In parts of concrete structures likely to be intermittently inundated, splashed or sprayed with sea water, the use of stainless steel reinforcement should be considered, either throughout the exposed section of the structure, or in combination with carbon steel reinforcement. Stainless steels equivalent to Grade 1.4436 (316) or 1.4429

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(316LN), 1.4301 (304) and Duplex 1.4462 (2205) should be used. (Grade 1.4301 (304) is not recommended for use in areas in C2 exposure conditions). Stainless steel, when used in combination with carbon steel reinforcement, may be used in the more exposed locations, e.g., the corner bars in beam soffits, and for thin reinforcing steel elements such as ties and stirrups. Stainless steel reinforcement should comply with BS 6744. The ductility properties of stainless steel reinforcement should be ascertained when applying the structural design rules of AS 3600.

(c) Galvanizing of carbon steel reinforcement may delay the onset of corrosion compared with normal (uncoated) carbon steel in a maritime environment, provided the measures outlined below are taken. The galvanizing provides corrosion protection to the base steel due to its resistance to the effects of reduction in the pH of the concrete mass (the carbonation effect) and its higher chloride tolerance compared to normal steel. When using galvanized reinforcement, the provision of an adequate cover of a good quality concrete, as is necessary with normal carbon steel reinforcement, will provide the best overall result. Galvanizing of reinforcement should be by the hot-dip process and an average minimum coating mass of 600 g/m2 should be provided in accordance with AS/NZS 4680. For best performance, it is preferable for the galvanizing of reinforcement to be undertaken after all cutting, bending and welding of reinforcement cages is complete. In normal practice, repairs to cut ends and breaks in the coating should be undertaken following the recommendations in AS/NZS 4680. If galvanized reinforcement is used, all steel within the member should be galvanized to prevent potential sacrificial corrosion of the galvanized coating. If selective use is made of galvanized reinforcement or other components in concrete (e.g., galvanized bolts, fittings, attachment plates), it is important that the point of connection to normal steel reinforcement be deeply embedded. The use of galvanized reinforcement in conjunction with stainless steel is not recommended.

(d) Epoxy coating or other enveloping protection system for steel reinforcement is not recommended for concrete in a marine environment.

(e) Cathodic protection of carbon steel reinforcement may be used to extend the design life of a maritime structure, although this should only be used when the designer is confident that the system will remain operational and will be routinely maintained. (In parts of maritime structures with exposure classification C2 (see Table 6.3), bonding of all reinforcement cages by welding every bar intersection to facilitate the later introduction of cathodic protection of the reinforcement should be considered).

6.3.5 Prestressing steel 6.3.5.1 General The use of prestressed concrete in a marine environment requires additional consideration to be given to the protection of the highly stressed steel elements. While the permanent compression in such concrete structures aids in reducing saltwater penetration through cracks, the effect of chlorides on highly stressed strand and wire can produce unpredictable structural performance. These effects include chloride corrosion and stress corrosion (embrittlement), which can result in sudden tensile failures in concrete members. Often these failures are unpredictable because the small cross-section of the high-strength steel will undergo substantial strength losses without any evidence on the concrete surface, (unlike the staining and spalling behaviour of conventional steel reinforcement).

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Exposed ends of prestressing steel should be cut back and protected with a suitable impermeable mortar to prevent ingress of water. 6.3.5.2 Post-tensioned members Post-tensioned members, with strand grouted within fully enclosed waterproof ducts of heavy-gauge inert materials (e.g., 3 mm–5 mm thick walled PVC or HDPE) can be expected to have substantial design life. 6.3.5.3 Pre-tensioned members When using pre-tensioned members stressed with unprotected carbon steel wires (protected only by concrete cover), consideration should be given to minimizing the chloride ion content arising from aggregates and any admixtures used, and to the use of other preventative forms of future ingress of chloride ions (concrete additives for corrosion inhibitors, pore-blockers, surface sealants etc.). It is recommended that in a marine environment where pre-tension wire or strand is used, non-prestressed carbon steel be used. This non-prestressed steel should be located in the most exposed section of the element to provide an early indication of chloride-induced corrosion. It is suggested that such non-prestressed reinforcement provide at least 40% of the total prestressed and non-prestressed reinforcement capacity. 6.3.6 Exposure classifications The exposure classifications given in Table 6.3 amplify those given in Table 4.3 of AS 3600. Reinforcement in concrete permanently submerged in sea water suffers only limited corrosion. However, in the splash (tidal) zone, where the concrete is alternately wet and dry, rapid corrosion is the consequence of chloride concentration and penetration, together with the high availability of oxygen and presence of moisture in the concrete. In this regard, special consideration should be given to the effect of saltwater splash due to reflective waves off rear walls and rock revetments at the landward end of maritime structures.

TABLE 6.3 EXPOSURE CLASSIFICATIONS

Exposure classification Exposure environment Reinforced or

prestressed members Members permanently 500 mm below the seabed A2 Members permanently submerged 1 m below lowest sea water level to 500 mm below seabed level B2

Spray zone, (i.e., exposed to airborne salt spray, but not in splash zone e.g., the top side of deck slabs) C1

Splash zone, from 1 m below water level up to 1 m above wave crest levels on vertical structures, and all exposed soffits of structures over the sea

C2

6.3.7 Cover to reinforcement 6.3.7.1 General The cover for low carbon steel bars should be not less than those shown in Tables 6.4 and 6.5 as appropriate. These covers can vary within the deviation from specified position as prescribed in AS 3600 (that is, within the appropriate tolerances).

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TABLE 6.4 MINIMUM COVER TO REINFORCING STEEL—STANDARD

COMPACTION CONCRETE Minimum cover (mm) Exposure classification

f′c = 40 MPa f′c = 50 MPa A2 40 30 B2 50 40 C1 70 50 C2 75 65

TABLE 6.5 MINIMUM COVER TO REINFORCING STEEL—INTENSE

COMPACTION CONCRETE Minimum cover (mm) Exposure classification

f′c = 40 MPa f′c = 50 MPa A2 35 30 B2 40 30 C1 60 45 C2 65 60

NOTES TO TABLES 6.4 AND 6.5: 1 A design life of 25 years can be expected where the above tables are

adopted for cover to reinforcement. Engineering judgement is required where a longer design life is required. Additional measures that may be considered include the use of low corrosion rate reinforcement (stainless steel); galvanized reinforcement (in combination with other measures); especially designed concrete mixes; use of additives or coatings such as organic or inorganic pore blocker concrete admixtures; chemical corrosion inhibitor admixtures; hydrophobic surface sealants (silanes) or other proven systems. These may be combined in appropriate circumstances with cathodic protection systems.

2 Where galvanized reinforcement is used, cover to steel should not be reduced.

3 Where stainless steel AISI 1.4436 (316), or higher grade stainless steel reinforcement is used, cover to steel may be reduced to 30 mm. Where stainless steel and carbon steel are used together in a member, the minimum cover given in the Tables above should apply.

4 For temporary structures, with a design life of less than 5 years, cover may be reduced by 25% from the values in Table 6.4 (except that minimum cover to steel should be 30 mm).

6.3.7.2 Crack control Cracking in concrete maritime structures can lead to reinforcement corrosion as well as aesthetically unattractive structures. To enhance durability, limiting the widths of cracks under serviceability conditions can be achieved by designing structures with low stresses in the steel reinforcement. Table 6.6 provides maximum recommended stress in carbon steel reinforcement for maritime structures in exposure classification C1 and C2. The structures have to be also designed for other relevant limit states including both stability and strength.

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TABLE 6.6 MAXIMUM ALLOWABLE REINFORCEMENT STEEL

STRESS AT SERVICEABILITY LIMIT STATE db (mm) ≤12 16 20 ≥24 fs (MPa) 185 175 160 150

In elements with exposure classification A2 and B2, the tensile stress in steel reinforcement may be increased to the limits provided in AS 3600 for crack control. Prestressed concrete structures should be designed to remain uncracked throughout the service load range. 6.3.7.3 Embedded Items Items that may be corroded by the saltwater environment should not be embedded in the cover zone. No potential corrosion path should be created by any material such as conduits or bar chairs, which if corroded, would compromise the concrete cover to the reinforcement. Metal items that protrude from the concrete surface should be insulated from steel reinforcement, so that galvanic cells between the reinforcing steel and the exposed metal cannot occur. For example, exposed stainless steel fitments or bolts, etc., should be electrically isolated from the reinforcement cage. Plastic or mild steel bar chairs should not be used. Bar chairs comprising stainless steel or precast concrete blocks of high density and strength (preferably stronger than the concrete to be placed) are an acceptable method of supporting reinforcing steel.

6.4 STEEL 6.4.1 General Steel is a suitable material for the construction of maritime structures; however, the decrease in steel durability after exposure to sea water should be considered when using carbon steel in the marine environment. During design, designers should consider methods that protect and maintain the steel members, as well as methods of installation and connection of steel members to prevent damage to pre-applied protective systems. The selection of the shape of steel members may not always be based on the most efficient system with regard to strength, but should be selected to allow the easy application and maintenance of protective coatings to allow improved durability. For example, tubular members are easier to coat and wrap than flanged or angle sections. Tubular members can be protected with thick inert applied coatings in factory conditions, or may be wrapped in purpose-designed materials applied after installation. 6.4.2 Stainless steel Where stainless steel is used in fabricated maritime structures, consideration needs to be given to grade selection, surface finish and proper welding procedures. Grade 1.4436 (316) or Grade 1.4462 (2205) should be selected for additional strength and corrosion resistance for maritime applications. Corrosion resistance of stainless steel increases with finer surface finishes. Corrosion of stainless steel in the form of surface discolouration (tea-staining) may be reduced by specifying high quality surface finish.

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Stainless steel should be used cautiously in anaerobic conditions, such as mud. If scratching or abrasion does not damage the protective surface oxide during installation or service then stainless steel can perform well. However, if the surface oxide is damaged then some air/oxygen should be available to allow the protective film to repair. Stagnant conditions may also be a source of microbiologically influenced corrosion, which can attack many metals including stainless steels. For further information refer to AS/NZS 1554.6, AS/NZS 2312 and AS/NZS 4673. 6.4.3 Material requirements Steel structures should comply with AS 4100, and the relevant standards relating to manufacture and rolling and milling of steel products as listed in AS 4100. 6.4.4 Steel protection systems 6.4.4.1 General Steel surface protection systems have been developed for various structural steel elements and corrosion environments. Damage caused by corrosion in the various marine environments can be attributed to varying physical processes such as rapid oxidation in the wet, salt, surface conditions, exacerbated by wave action and seabed abrasion, as well as wear and tear from maritime operations (chafing, flexing). These various forms of corrosion and damage require different protection systems. Damage caused to steel protection systems, at the time of construction and erection, must be repairable. Normal activities such as installing piles, cutting and welding steel members, and site drilling and bolting can cause damage to the protection system. In addition, the protective systems should be capable of repair/replacement during scheduled maintenance, at the end of the specified maintenance-free period. Elements permanently buried in the seabed or permanently immersed in sea water, generally have low corrosion rates and an annual corrosion allowance can account for the corrosion of the element (see Clause 6.4.4.7). Consideration should be given to the type of coating selected; the thickness of the coating system; the method of application; surface preparation; and the implementation of a suitable inspection and test procedure to assess the effectiveness of the applied system. 6.4.4.2 Jacket systems The encapsulation of steel members inside protective jackets (e.g., HDPE pipe, concrete jackets) is a suitable method of providing long-term protection to members such as steel piles. The jackets must extend a safe distance below seabed level, taking into account any future scour, which may result from propeller wash, stream flow or similar. 6.4.4.3 Applied coatings The application of thick (1 to 5 mm thick) inert materials (e.g., urethane, polyethylene etc), under factory conditions, is a suitable method for protecting piles or substructure members in aggressive environments. 6.4.4.4 Wrapping systems The use of corrosion inhibiting fabrics (e.g., petrolatum-tape) to wrap piles or substructure members is a suitable method for protecting members exposed to an aggressive environment (splash and spray zone). 6.4.4.5 Painting systems The use of inert, high build paint systems, such as epoxy paints, are suitable for the protection of steel structures in the splash zone. Paint systems should be able to be re-applied to old surfaces, to allow for repair and maintenance.

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6.4.4.6 Metallic coatings Thin metal coatings and hot dip galvanizing are suitable methods for protecting steel in some environments; however, due to the solubility of most metal corrosion products, such systems are not suitable where the surfaces will be subject to immersion or driven spray. 6.4.4.7 Corrosion allowance for permanently submerged steel Where no protection systems are to be applied, e.g., in a steel section buried below the seabed or a section permanently submerged, protection of the steel may be provided by providing an allowance for corrosion and subsequent loss of steel cross-sectional area. Where a corrosion allowance is to be used to protect submerged steel members, corrosion rates should not be less than those tabulated in Table 6.7, unless test data extending over an acceptable duration validates a lower rate for a particular location.

TABLE 6.7 CORROSION ALLOWANCE FOR STEEL SECTIONS

(PERMANENTLY SUBMERGED IN SEA WATER) Exposure

classification Condition Annual corrosion rate (mm)

Mild Permanently buried in seabed (see Note) 0.01

Moderate Cold water (south of 30°S) and near the mud line 0.05

Strong Tropical/Subtropical water (north of 30°S) 0.10

NOTE: The influence of ‘microbiologically induced corrosion’ (in anaerobic conditions below seabed) or ‘accelerated low water corrosion’ (about low water level) should be examined. These influences may produce corrosion rates significantly higher than those above.

6.4.5 Member sizes Steel members should be selected to be robust and have adequate reserve of strength to allow for corrosion and unpredicted loads for structures with a design life in excess of 5 years. Designers should consider the following: (a) Structural members exposed on both faces should not have a web or flange thickness

less than 8 mm. Sealed tubular members may have a wall thickness of 4 mm. Plate thickness on pontoons, protected on the inside face by a suitable paint coating system may be reduced to 4 mm, but exposed decks should have minimum thickness of 6 mm.

(b) The minimum bolt size for structural connections should be 20 mm for carbon steel and 12 mm for stainless steel. Tie rods should be of similar diameters.

(c) All steelwork should be designed to be free-draining, with no pockets that may trap water or sediment.

(d) Hollow members (tubular piles, rolled hollow sections) should be sealed to prevent corrosion on the inside face.

6.4.6 Cathodic protection Cathodic protection for steel structures is only applicable for parts of the structure permanently immersed in water. Cathodic protection should be installed in accordance with AS/NZS 2832.

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Where cathodic protection is used and regular maintenance of the structure is unlikely, sacrificial anodes should be used with or without a protective paint system. Where paint systems are used, the cathodic protection should be designed to provide protection as the paint system deteriorates. Impressed current cathodic protection may be used where the system is likely to be well maintained and where stray currents do not interfere with the protection system, or where currents from vessels will not negate the effect of the system. Caution should be exercised to avoid stray currents from cathodic protection systems affecting moored vessels and unprotected structures.

6.5 TIMBER 6.5.1 General Timber has many applications in maritime structures, particularly in lighter duty recreational facilities (waterfront boardwalks, small craft facilities, piers, jetties and similar). Timber may be used for the construction of the total structure including piles, headstocks, stringers, bearers and decking, or timber can be effectively used in conjunction with other materials to provide economic, and durable structures. To alleviate the normal problems of fungal attack caused by rainwater or other sources of moisture on timber, concrete decks may be used on timber resulting in durable and economic structures. Timber may be used for fendering systems and other wearing surfaces, as well as for fender piles on structures predominantly constructed from concrete and/or steel. Generally timber would not be used as the principal structural medium for a facility with a design life greater than 25 years and decks classed above Class 10 (see Table 5.1). Timber for maritime structures should generally be hardwood timber of Natural Durability Class 1 or 2, in accordance with AS 5604. 6.5.2 Immersed timber Timbers in contact with tidal saltwater should be selected for their natural resistance to marine borer attack e.g., Syncarpia glomulifera (Turpentine) or alternatively may be treated with preservative impregnation and/or coatings/sheathing/jacketing (impermeable), to resist marine organisms. Where Turpentine timber piles are used, it is desirable to have the section of pile in the water column free of interruptions to the bark (e.g., where branches may have been trimmed) as these areas provide a flaw in the pile’s natural protection to marine organisms. Similarly, timber piles below high water level should not be cut or drilled. To minimize the risk of marine organisms attacking the exposed inner wood of cut or drilled timber, a suitable barrier material should be applied. Preservation of timber for use in piles or other structures below water level should be in accordance with AS 1604. Such preserved timber should not be cut or drilled where it will be immersed. 6.5.3 Timbers above water level Timber members located above the level of high tide are not at risk of marine borer attack; however, they should be of a species resistant to fungal attack due to standing fresh water and termite attack. Substructure timbers should be protected from standing fresh water by a layer of aluminium sarking spiked to the top face of the timber, turned down at each side (see Figure 6.1).

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FIGURE 6.1 SARKING DETAILS

Exposed timber pile tops should have waterproof caps moulded to the top of the trimmed pile. A steel ring should be fitted around the top of the pile to minimise splitting after installation. Other vertical timber sections should where possible be cut at an angle to facilitate shedding of moisture. 6.5.4 Decking In the design of timber decks used for pedestrian access, it is necessary to ensure that trip hazards will not be caused by differences in plank thickness or warping due to drying. To reduce trip hazards, decking timbers should generally be machined on the underside to ensure uniform thickness. The topside of the timber should be rough sawn to reduce slip hazard when wet. Deck planks should be ‘back sawn’ sections and laid with the timber’s ‘heart’ side as the underside of the deck. 6.5.5 Finishes Increased protection from environmental deterioration may be achieved by the application of coatings to timber, including paint finishes, epoxy coatings, in situ preservative applications or by wrapping the member with protective wrapping materials. Interfaces of joints and drilled holes, along with timber end-grain should be protected by application of moisture repellent and decay inhibiting preservatives. Products containing copper naphthenate chemical, which may contain diffusing properties to penetrate below the wood’s surface, are effective as decay inhibitors.

NOTE: Where a structure is installed adjacent to oyster leases or sensitive fishing grounds, chemically treated piles should not be used. Piles in such situations should employ coatings, sheathing, jacketing, etc.

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APPENDIX A CONTAINER WHARF DECK LOADINGS

A1 GENERAL Container wharf deck loadings relate to the wharf-side loads from transporting and stacking containers for loading/unloading container ships. The loads do not reflect loads from storage of containers in container yards, which may be stacked several containers high, as such storage is specific to each port. In the absence of more specific equipment specifications, loads and dimensions given in Table A1, which represent typical loads and dimensions, should be applied to design in order to reasonably accommodate container operations. These loads do not include dynamic effects. Adequate provision for these effects should be allowed.

A2 CONTAINER STACKING Containers may be stacked on the apron beside a vessel while awaiting transport or loading. Concentrated corner loads are as given in Table A1.

TABLE A1 STACKING LOADS FROM CONTAINERS ON

WHARF APRONS

Storage method Load (kN)

Dimensions of loaded

area (mm) Single container 230 150 × 150

Line of containers 380 150 × 400 Block of containers 750 400 × 400

NOTE: This is for 40 ft containers that are 12.2 m long and 2.4 m wide, stacked 2 high, supported at each corner.

A3 CONTAINER TRANSPORT Forklift trucks and reach-stackers to transport 40 ft containers have the following wheel loads: LADEN Maximum front wheel load 300 kN (4 No) Maximum rear wheel load 100 kN (2 No) (Tyre pressure of 750 kPa) UNLADEN Maximum front wheel load 100 kN (4 No) Maximum rear wheel load 200 kN (2 No) The arrangement of such loads is shown in Figure A1. Straddle carriers have a maximum wheel load of 150 kN and an arrangement as shown in Figure A2.

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FIGURE A1 FORKLIFT TRUCK AND REACH STACKER WHEEL ARRANGEMENT

FIGURE A2 STRADDLE CARRIER WHEEL ARRANGEMENT

A4 CRANE RAILS Container quay cranes (CQCs) operate on crane rails set into the wharf deck, parallel to the wharf quayline, with a rail gauge commonly ranging between 15m and 30m (see Figure A3). The CQC loading on the crane rail (and so to the wharf structure) varies widely with each specific crane installation. Crane weights and corner loads vary with crane capacity, rail gauge, operational and extreme wind conditions; these loads will have to be assessed for each installation. Application of this load into the wharf (rail) may be regulated by the number and spacing of the wheels at each corner. A general design load of 750 kN/m will accommodate most CQC loadings. The length of applied load will depend on the crane design and conditions; however, a nominal loaded length of 8 m for one leg of the CQC will accommodate the typical corner loads shown in Figure A3 under most conditions. Bogie arrangements with up to 12 wheels per corner, with a maximum length of 12 m (12 wheels at 1.1 m centres) can reduce the design load to 500 kN/m. Special attention should be given to CQC loads in cyclone areas, with provision for higher loads in tie-down zones (increased wheel loads, uplift loads, longitudinal loads into tie-down anchors and transverse loads into the rails). Travel stop buffer loads should also be considered.

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DIMENSIONS IN METRES

FIGURE A3 TYPICAL CONTAINER QUAY CRANE CONFIGURATION FOR POST-PANAMAX VESSELS

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APPENDIX B BERTHING ENERGIES AND LOADS

B1 SCOPE This Appendix provides a commentary on methods for determining berthing energies and corresponding reaction loads due to vessels berthing at a wharf or structure and for the design of fender systems.

B2 GENERAL A widely accepted guideline for design of fender systems for commercial shipping is provided by PIANC International Navigation Association, ‘Guidelines for the Design of Fender Systems: 2002’, Report of Working Group 33 of the Maritime Navigation Commission. Unless more specific design practices apply for a particular port facility, it is recommended to follow these guidelines for design of fender systems for vessels over 10 000 DWT. The PIANC Guidelines provide a comprehensive coverage of all aspects of fender design, including— (a) development of the berthing model (contact with single/multiple fenders); (b) fender geometry: spacing; accommodation for bulbous bows; (c) description of fender systems; (d) detailed fender design; (e) fender selection; (f) whole of life considerations; (g) special cases—vessel class, vessel to vessel, flexible dolphins and berthing beams; (h) procedure to determine and report the performance of marine fenders; (i) procedure to determine and report the performance of pneumatic fenders; (j) vessel dimensions; (k) selection of fender size—case studies; and (l) guidelines for specification writing.

B3 APPROACH VELOCITY The PIANC Guidelines presents two methods for determining design approach velocity, one of which is presented in this Appendix (see Figure B1).

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47 AS 4997—2005


FIGURE B1 BERTHING VELOCITIES—VESSELS > 1000 t (Source: Brolsma et al, (1977) Design berthing velocity (mean value) as a function of

navigation conditions and size of vessel)

Figure B1 distinguishes five navigation conditions, as follows: (a) Good berthing—sheltered. (b) Difficult berthing—sheltered. (c) Easy berthing—exposed. (d) Good berthing—exposed. (e) Difficult berthing—exposed. The velocities assumed in Figure B1 assume that all berthings are tug-assisted. The impact data shows low approach values for large vessels, which may be exceeded in adverse conditions. Similarly, the velocity indicated for vessels below 10 000 t are high, and it is considered that maximum velocity for berthing may be taken as 0.6 m/sec. Caution is required when applying the velocity values at these extremes of Figure B1. For approach velocities for vessels below 1 000 t, guidance in this range is presented in Table B1.

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TABLE B1 BERTHING VELOCITIES—VESSELS < 1000 t

Vessel class Tonnage range Exposure conditions1,2,3 Vn

(m/sec)

Mild 0.20 Moderate 0.25 Private vessels Up to 10 t

Severe 0.30 0.15 0.20 Private vessels Over 10 t

Mild Moderate

Severe 0.25 0.20 0.25 Commercial charter/

cruise vessel Up to 1000 t Mild

Moderate Severe 0.30

0.30 0.35 Ferries Up to 100 t

Mild Moderate

Severe 0.40 0.25 0.30 Ferries Over 100 t

Mild Moderate

Severe 0.35 NOTES: 1 ‘Mild’ exposure has current speeds less than 0.5 knots; fair weather prevailing wind speeds

less than 10 knots; and wave heights less than 10% of the moulded draft of the design vessel. 2 ‘Moderate’ exposure has current speeds between 0.5 knots and 1.0 knot; or fair weather wind

speeds between 10 knots and 15 knots; or fair weather wave heights between 10% and 20% of moulded depth of vessel.

3 ‘Severe’ exposure is when the environmental conditions exceed any of the current wind or wave conditions for a moderate exposure.

B4 FENDER REACTION LOADS The reaction load from fenders should be determined from the manufacturer’s performance charts. This load should be factored to account for— (a) manufacturing tolerance (5–10%); (b) berthing/compression speed; (c) angular compression; and (d) temperature. Performance figures are usually valid for fenders that have been pre-conditioned by compression to the rated values. Fenders should be specified to be pre-conditioned before installation to avoid higher than expected reactions on the first maximum compression by a vessel. The PIANC Guidelines discuss all these aspects of fender reaction forces.

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49 AS 4997—2005


B5 LOADS ASSOCIATED WITH BERTHING IMPACTS Associated with berthing impact loads are longitudinal and vertical loads as the vessel slides along the face of the fender and heaves or rolls under the reaction of the impact. Typical friction factors, vertical and horizontal, depend on fender face material, these can vary from 20% for UHMWPE to 40% for timber. These lateral loads are calculated as the maximum impact reaction load (on the fender system or structure), factored by the coefficient of friction between the sliding surfaces.

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APPENDIX C MOORING LOADS

Vessels berthed at structures will exert loads through fenders reactions and through mooring lines, resulting from loads acting on the vessels. These loads include wind, current and wave forces on the vessel, as well as manoeuvring forces when vessels are berthing and departing berths. Refer to Section 5 for calculation of wind actions on a vessel. In determining the wind load from a vessel on any individual structure, recognition should be given to the variability of stiffness of the lines connecting the vessel to the several mooring points. The design lateral load on an individual mooring point should be 20% more than the evenly distributed component of load established from the geometry of the moored vessel. Refer also to OCIMF papers or BS 6349 for calculation of wind and current loads on moored vessels. Mooring forces should consider loads applied +45° and −15° to the horizontal plane, in any direction from the forward arc from the wharf. Mooring forces from vessel manoeuvring loads should be considered. These forces are a result of vessels using bollards to slow vessels down or to assist in turning vessels while using rudders and propulsion systems. The design action used in the structural design should be equal to the rated capacity of the bollard or mooring cleat, as determined by Table C1. Where vessels may be exposed to conditions other than mild, the bollard capacity should by 25%.

TABLE C1 MOORING FORCES FOR

SHELTERED CONDITIONS Vessel displacement

(tonnes) Bollard capacity

kN Up to 50 50 50 to 200 100

200 to 1000 200 1000 to 10 000 300

10 000 to 20 000 500 20 000 to 50 000 800

50 000 to 100 000 1 000 100 000 to 200 000 1 500

Above 200 000 2 000

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NOTES

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NOTES

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Standards Australia Standards Australia is an independent company, limited by guarantee, which prepares and publishes most of the voluntary technical and commercial standards used in Australia. These standards are developed through an open process of consultation and consensus, in which all interested parties are invited to participate. Through a Memorandum of Understanding with the Commonwealth government, Standards Australia is recognized as Australia’s peak national standards body. For further information on Standards Australia visit us at

www.standards.org.au

Australian Standards Australian Standards are prepared by committees of experts from industry, governments, consumers and other relevant sectors. The requirements or recommendations contained in published Standards are a consensus of the views of representative interests and also take account of comments received from other sources. They reflect the latest scientific and industry experience. Australian Standards are kept under continuous review after publication and are updated regularly to take account of changing technology.

International Involvement Standards Australia is responsible for ensuring that the Australian viewpoint is considered in the formulation of international Standards and that the latest international experience is incorporated in national Standards. This role is vital in assisting local industry to compete in international markets. Standards Australia represents Australia at both ISO (The International Organization for Standardization) and the International Electrotechnical Commission (IEC).

Electronic Standards All Australian Standards are available in electronic editions, either downloaded individually from our web site, or via On-Line and DVD subscription services. For more information phone 1300 65 46 46 or visit Standards Web Shop at www.standards.com.au

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GPO Box 476 Sydney NSW 2001 Administration Phone (02) 8206 6000 Fax (02) 8206 6001 Email [email protected] Customer Service Phone 1300 65 46 46 Fax 1300 65 49 49 Email [email protected] Internet www.standards.org.au

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AS 4997-2005