Ports and Horbour

8/4/2019 Ports and Horbour

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26Ports andMaritime Works

C J Evans MA(Cantab), FEng, FICE,FIStructEWallace Evans and Partners

Contents

26.1 Sitting of ports and harbours 26/3

26.1.1 Design of harbours 26/326.1.2 Sedimentation 26/3

26.2 Port planning 26/3

26.2.1 Types of cargoes 26/3

26.2.2 Sizes and types of vessels to be catered

for 26/4

26.2.3 Types of vessels 26/4

26.2.4 Methods of cargo handling 26/5

26.2.5 Land area 26/5

26.2.6 Access 26/5

26.2.7 Other considerations 26/5

26.3 Navigation 26/6

26.3.1 Requirements 26/6

26.4 Design of maritime structures 26/7

26.5 Marginal berths 26/7

26.6 Piers and jetties 26/9

26.6.1 Piers 26/9

26.6.2 Jetties 26/9

26.7 Dolphins 26/10

26.7.1 Breasting dolphins 26/1026.7.2 Mooring dolphins 26/10

26.8 Roll-on roll-off berths 26/10

26.9 Loads 26/12

26.9.1 Dead load 26/1226.9.2 Superimposed dead load 26/12

26.9.3 Imposed load 26/12

26.9.4 Soil and differential water load 26/12

26.9.5 Environmental loads 26/12

26.10 Fendering 26/12

26.10.1 Introduction 26/12

26.10.2 Fendering systems 26/13

26.10.3 Design of an attached fendering system 26/13

26.10.4 The basic energy equation 26/13

26.10.5 The factor of safety 26/15

26.10.6 Structural considerations 26/15

26.11 Locks 26/15

26.11.1 Lock dimensions 26/15

26.11.2 Lock gates 26/15

26.12 Pavements 26/15

26.13 Durability and maintenance 26/16

References 26/16

Bibliography 26/16


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The f unc t ion of a port is to provide an in terface between tw omodes of t ransport - land and sea - for cargo and passengers.The requirements for sea transport are: (1 ) an adequate area ofwater of sufficient depth for naviga t ion an d berthing; an d(2 ) adequate shelter so that berthing, loading an d unloadingcan be carried out safely an d efficiently. The requirements fo rthe landside are: (1) adequate land area for working space,loading an d unloading vessels and for handling an d storage ofcargoes; and (2) suita ble access to areas served by the port .

26.1 Siting pf ports and harboursThe si t ing of a port is generally dictated by commercial an deconomic requirements, particularly in relation to land trans-por ta t ion . A na tura l harbour is to be preferred in order to avoidth e necessity of expensive breakwaters, even though somedredging may be required to provide the necessary area of deepwater. If the material to be dredged is suitable, land reclamationmay be possible using th e dredged material to provide land fo rth e shore facilities o f a port .If a na tura l harbour is not available, breakwaters will berequired to provide adequate shelter. Breakwaters are normallyvery expensive however, an d this m u s t be weighed against an yaddi t ional t ransport costs and compared with the expenditureincurred at a port where breakwaters are no t required.In plann ing a new harbour invol ving breakwaters, co nsider-ation must be given to the following factors, in addition to thedesign of the breakwater itself (see Chapter 31 fo r design ofbreakwaters): (1 ) waves; (2 ) littoral drift an d sedimentat ion;(3 ) tides an d currents; and (4) naviga t ion .26.1.1 Design of harboursThe main purpose of breakwaters is to provide protect ion fromwaves, and the biggest wave reduction is effected with th esmallest entrance sited remote from th e direction of approach ofthe waves. However, this can cause difficulty when approachingth e entrance with heavy seas abeam th e vessel. A s harbours ar enormally designed to serve as a harbour of refuge, i.e. aprotection to be sought by vessels during the height of a storm,it is common to site an entrance at a small angle to the heaviestsea, thereby improving accessibility at the expense o f smooth-ness within th e harbour.Wave-height reduction within a harbour is improved as thedistance from th e entrance, and the width parallel to the shore,increase. It is desirable to have wave-spending beaches - orarmoured slopes which absorb wave energy - facing thewaveswithin th e harbour, rather than vertical walls which reflectwaves an d could cause resonance resulting in significant in -creases of wave heights. Wave heights within a harbour arenormally predicted u sing numerical models or a phy sical model;in both cases, various breakwater alignments can be tested togive th e optimum alignment. A n empirical method fo r assessingwave heights within a harbour is given in the Stevenson formu la:

h p=H [(&/*)* - 0.027D* (1+I] (26.1)where /* p is the height of reduced wave at any point in theharbour, H is the height of wave at entrance, b is the breadth ofentrance, B is the breadth of harbour at P, being length of arcwith centre at midway of entrance an d radius D an d D is thedistance from entrance to point P.This formu la does not take into accoun t the result of anyreflection of waves. Fo r assessment of //, see Chapter 31.

26.1.2 SedimentationSedimentation in a harbour can arise f rom three sources:(1 ) l i t toral drift; (2) t idal movements; and (3) where a harbouris located at a r iver mouth, from th e river. The minimizing o fsedimentat ion in navigation channels, a t the entrance andwithin the harbour, is of prime importance in reducing the costof maintenance dredging.Lit toral drift occurs to some extent along most coastlines. Ifth e path of the drift is obstructed by a solid structure, th eheavier particles will accumulate on the drift side and thisaccumula t ion may well extend round to the inside. The f inerparticles of the drift, which outside th e harbour ar e kept insuspension by current velocities will, o n entering th e harbour ,no longer be maintained in suspension and will settle ou t .Lit toral drift normally occurs i n one direction, but a t certaint imes of the year or under some storm condit ions, th e directionof drift can be reversed. Litto ral drift is discussed in more detailin Chapter 31.Where a harb ou r is subjected to large tidal ranges, material insuspension will be brought i nto the harb ou r as the tide rises and,dur ing periods of slack tide, material will settle o n the,sea-bed.Where a harbour is at a river mouth, the material carried downby th e river is a fur ther source of sedimentat ion. The in teract ionof river flows and movements of the sea makes fo r fu r thercomplicat ions, with th e added difficulty of the difference indensity between fresh an d salt water.Predictions of sedimentation are best carried out by numeri-cal modelling. Physical models can also be used, bu t these can beless accurate - part icularly with fine material in suspension -because of the difficulty of scaling-down the fine particle sizes toth e scale of the model, and results should be treated withcau t ion .

26.2 Port planningThe planning of a new port or expansion or improvement o f anexisting one requires many factors to be taken into consider-at ion. Apart from passenger ferry terminals an d cruise shipterminals, ports ar e primarily provided for the handling o fcargo. Amongst th e factors to be considered are:(1 ) Nature of cargoes to be handled.(2 ) Sizes an d types of vessels to be catered for.(3 ) Method of cargo handling.(4) Land area an d operations.(5 ) Land access.26.2.1 Types of cargoesBetween 1960 an d 1980 a major revolut ion in the handling an dcarrying of maritime cargoes too k place and this has led to newconcepts in the design o f ships, ports an d land transportationsystems. Generally speaking, during this period emphasis wasgiven to handling and carrying cargoes in larger units, e.g.containers in the case of general cargo, and larger singleshipments o f bulk commo dit ies such as wheat an d oil, etc. Shipsizes also increased to o btain the benef its of the increased scaleof operat ion.26.2.1.1 General cargoesNonunitized (or break bulk) cargoes. These consist of smallconsignments requiring to be handled individually. The volumesnow being conveyed by this method are rapidly dimin ishing andnonunit ized working is practised only in areas where labour isplentiful.


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Unitized cargoes. Unitization of cargoes permitting largerunits of general cargo to be handled by mechanical equipment,soreplacing labour, has become attractive. Unitized cargoes canbe subdivided as follows:(1 ) Prepackaged. Certain dry-bulk cargoes, of which sawntimber is one, ar e packaged into larger standard-sized unitsfo r handling in unit sizes ranging up to 51. Packaging isusually done using metal strapping.(2 ) Palletized cargoes. These range from I t to 51 and are

suitable fo r handling by fork-lift trucks. Typical examplesare bagged commodities such as cement and flour, andboxed products. Standard pallet sizes, in metres, are asfollows:0.8x1.00 . 8 x 1 . 21 . 0 x 1 . 21 . 2 x 1 . 61 . 2 x 1 . 8

(3 ) Flats. These are usually 3.05 x 2.44m and 6.1Ox 2.44mcapable of carrying up to 101. Consignments can be of bothregular or irregular shape but require lashing down to theflat. They can be handled by fork-lift t rucks or a combi-nation of fork-lifts and low-wheel trailers.(4 ) International Organization fo r Standardization (ISO) con-tainers. Standard sizes are usually quoted in tonnes equiva-lent units (TEUs), an d those most commonly in use are:(a) 3.05 x 2.44 x 2.44 m (maximum load 101 or 0.5 TEU);(b) 6.10 x 2.44 x 2.44 m (maximum load 201or 1 TEU);(c ) 12.19 x 2.44 x 2.44 m (maximum load 40 1 or 2 TEU).These are sealed units, capable of being lifted from th ebottom by fork-lift t rucks or from the top at the ISO four-corner lock attachments by cranes and mobile equipment.They are also stackable. Specialized IS O containers havebeen developed as refrigerated and liquid tank units, bu t allare to the standardized overall dimensions and equippedwith the ISO universal han dling devices. Some of these, e.g.refrigerated units, require support services in the way ofelectrical power whilst in transit through the port.(5 ) Specialized forms. The in troduction of roll-on, roll-off(RoRo) ships allows cargoes in road trailers to be shippedeither with or wi thou t th e tract ion unit .

26.2.1.2 Bulk cargoesBulk cargoes fall in to tw o categories: (1 ) dry; and (2) l iquid.Comm odities of these types, more often than not, are shipped inpurpose-built vessels or carriers and are loaded and unloadedusing specialized berths or term inals equipped with m echanicalhandling systems suitable for the commodity being handled.Typical commodities are grain, mineral ores, timber, sugar,vegetable oils, mineral oil and petroleum products, liquid

Table 26.1Vessel type Approximate loadeddisplacementBulk carrier GRT x 1.2-1.3Con tainer vessels D W T x 1.4Passenger liners GR T x 1.0-1.1General cargo GRT x 2.0or D W T x 1.4^1.6

chemicals, liquefied petroleum gases (LPG) an d liquefiednatural gas.Some of these commodities ar e hazardous an d have to behandled and stored under statutory regulations.26.2.1.3 Miscellaneous tradesThere are a number of cargo trades which do not fall readilyinto th e above categories. A n example of this is the advent of thecar carrier solely handling cars fo r international distribution.

26.2.2 Sizes and types of vessels to be catered for26.2.2.1 ClassificationShips are classified under a n um ber of tonnages as follows.(1 ) Gross registered tonnage The value derived f rom divid-(GRT): ing the total interio r capacityof the vessel by 2.83 m 3, sub-ject to the provisions of appli-cable laws and regulations.(2 ) Net registered tonnage The gross tonnage of the vessel(NRT): minus th e tonnage equivalentof crew cabins, engine-rooms,etc.(3 ) Displacement tonnage: Indicates th e to tal mass of thevessel, and is obtained by mul-t iplying th e volume of the dis-placed sea water by the densityof sea water (1.03 t/ m 3 ) .(4 ) Dead weight tonn age Dead weight of a vessel is the(DWT): weight equivalent of the dis-placement tonnage minus th eballasted weight of the vessel.Consequently, i t indicates th eweight of the cargo, fuel, waterand all other i tems which canbe loaded aboard th e vessel.(5 ) Tonne measurement The value derived from divid-in g the cargo spaces of a vesselby 1 . 1 3 m 3 .The approximate relationships shown in Table 26.1 applybetween th e various tonnages. Fo r port engineering purposes,DW T is the most significant although, fo r calculat ing berthingenergies, the displacement of the vessel is required. The shippingindustry uses the long ton . This is almost the same as the metrictonne and for planning purposes can be treated as beinginterchangeable.

26.2.3 Types of vesselsVessels are generally categorized by the types of cargo theyhandle as follows.(1 ) General cargo. These generally carry nonunitized (break-bulk) cargoes and/or unitized cargoes, but can also carrysome containers. These range in size from small coasters(2000-3000 DWT) to long-distance vessels up to 30000D W T .(2 ) Container vessels. These are specially designed ships for thepurpose of carrying containers and can vary from small

feeder vessels c arrying perhaps 150 TEU up to the very largecontainer vessels (used on long se a routes) carrying up to4000 TEU and being of abou t 70000 DW T .


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(3 ) Roll-on roll-off vessels. These are specially designed to allowthe movement of cargo through stern or bow ramps byvehicular movements without the need for cranes or otherlifting devices, and are generally used on the shorter searoutes.(4 ) Bulk-cargo vessels. These are normally designed specificallyfor a particular trade, such as iron ore, coal, grain sugar, etc.and can range from small vessels of 20 000 D WT up to largebulk carriers of up to 60 000 DW T .(5 ) Tankers. These are designed for liquid bulk cargoes and canrange from small vessels of 20 000 DW T up to the very largeoil tanker of up to 1 mill ion D WT.Typical relationships of dimensions for variou s types of vesselsare shown in Figures 26.1 to 26.4.Certain characteristics of vessels may also need to be takeninto account. Some vessels are equipped with bow thrusters forease of manoeuvr ing , an d these have been known to causedamage to quay walls. Problems can also occur with vessels thathave bulbous bows, where the projecting bow located belowwater can cause damage to piled structures.26.2.3.1 Vessel characteristicsIn planning a port development, knowledge of the followingcharacteristics of vessels likely to use the port is required inaddition to the dimensions of vessels (length, beam an d draft).(1 ) Ship layou ts, including the locations and dimensions oframps an d hatches, loaded an d unloaded deck heights,superstructure positions and clearances for dockside cranes.(2 ) Handling characteristics o f ships fo r manoeuvr ing an dturn ing operations.(3 ) Windage areas of ships to assess forces on berths.(4 ) Ship mooring line sizes an d capacities fo r bollard pulls.(5 ) Deck crane capacities and reaches.26.2.4 Methods of cargo handlingThese will depend largely on the nature of the cargoes and thetypes of vessels likely to use the port . The most importantconsideration is whether dockside cranes are required orwhether ships' own lifting gear will be used fo r loading an dunloading. Apar t f rom cranes, cargo-handling equipment canrange from fork-lift trucks, which can have a capacity from 3 0to 4 0 O k N fo r general cargo, to special container-handlingequipment. The latter can be large fork-lift t rucks (capacity 200to 42 0 kN) straddle carr iers and g antry cranes (rubber tyred oron rails).26.2.5 Land areaThis depends on: (1) th roughput o f cargo; (2 ) type of cargo;(3) methods of cargo handling; and (4) length of t ime cargoremains in the port . A modern general cargo berth is normally2 0 O m long and 2 0 O m or more deep. Thus, an area of200 x 200 m , or 4 ha, is required. W ith efficient cargo handling,this will handle approximately 250 0001 of cargo per year. Acontainer berth requires more land behind th e berth to maxi-mize the throughput. Container berths are generally 300 m longor greater and with up to 20 0 to 800 m depth, althou gh this canbe reduced if containers are stacked. The area can thereforerange up to abou t 20 ha which would handle up to abou t 1million t o f cargo per year. However, th e land requirementsmust be investigated fo r individua l cases according to thefactors mentioned above. With a general cargo area, part of theland will be utilized by transit sheds and warehousing. In acontainer berth, the land area will largely be open fo r storage of

D e a d w e i g h t ( ' 0 0 O t )F i g u r e 2 6 .4 T y p i c a l l e n g t h s f o r g e n e r a l c a rg o R o R o v e s s e l s ,t a n k e r s a n d b u lk c a r ri e rscon tainers with sheds for filling and em ptyin g containers, unlessthese operations are carried out at an inland depot away fromthe port .26.2.6 AccessAccess can be either by road, rail or both; or, in the case ofliquid cargoes, by pipeline.26.2.7 Other considerationsOther factors requir ing considerat ion in the p l a n n i n g o f por tdevelopments include:(1 ) Tugs an d pilotage.(2 ) Security and policing services.

D e a d w e i g h t ( ' 0 O O t )F i g u r e 2 6 . 3 T y p i c a l o r e c a r r i e r d i m e n s i o n s

D e a d w e i g h t ( ' 0 0 O t )Figure 2 6 . 2 T y p i c a l o i l t a n k e r d i m e n s i o n s

D e a d w e i g h t ( ' 0 0 O t )F i g u r e 2 6 . 1 T y p i c a l g e n e r a l c a r g o a n d R o R o v e s s e l d i m e n s i o n s

Drafm)

Beamm)

Drafm)

Beamm)

Drafm)

Beamm)

Overalengthm)


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(3) Fuel bunkering facili t ies.(4) Equipment maintenance facilities.(5 ) Services to ships - water, electricity, sewerage, telephone.(6) Rest rooms, canteens an d offices, etc.(7 ) Post offices.(8) Customs an d immigrat ion arrangements .

26.3 NavigationThe navigat ion requirements o f a harbou r involve three aspects:(1 ) th e approach channel ; (2) the entrance; and (3) themanoeuvring area wi thin th e harbour .26.3.1 Requirements26.3.1.1 Channel widthChannel width is governed by many fac tors , the most impo rtantof which may be summarized as follows:(1 ) The vessel dimensions; in particular, the beam of the largestvessel using th e port .(2 ) T he orientat ion an d s t rength of the c urren t s and the expo-

sure to wind an d wave ac t ion (which can cause vessels toy aw an d crab).(3) The speed an d manoeuvrab i l i t y of the vessels and theexpertise of the pilots.(4) The operating pattern of vessel movements, i .e. whethervessels ar e allowed to pass o r whether a phased one-waysystem is operated.(5) The proximity of the vessels to the channel banks (the effectof which is to promote addi t ional yaw).(6 ) The channel depth; in part icular, th e underkeel clearance.Variou s methods, inc ludin g ship deviation studies and scale-model methods, have been employed to assess channel widthan d various recommendat ions have been publ ished. Bri t i shStandard 63491 gives the fol lowing recommendat ions .(1 ) 4 to 6 x beam: large vessels, one-way traffic o n l y .(2 ) 6 to 8 x beam: smaller vessels passing.(3) 5 to 7 x beam: large ta nkers.Other studies have produced recommendat ions in the formshown in Table 26.2, which gives an example fo r a design vesselof length L of 260 m and breadth B of 40 m. The manoeuvr inglane is denned as that port ion of the channel wi thin which th eship may manoeuvre wi thout encroaching on the safe bankclearance an d witho ut approaching ano ther ship so closely thatdangerous interference between ships would occur. A s vesselspass each other, in terac t ive hydrodynamic effects occur asillustrated in Figure 26.5.T a b l e 2 6 . 2

F i g u r e 2 6 . 5 H y d r o d y n a m ic e f fe c t s o f s h ip s p a s s i n g in c h a n n e l s ,( a ) 6 o w s a b r e a s t : b o w s y a w a w a y , b u t b a n k s u c t io n o p p o s e s t h i st e n d e n c y ( s h e e r t o s t a r b o a r d ) ; ( b ) b o w s a p p r o a c h s t e r n s , b o w sy a w t o w a r d l o w w a t e r a n d t h e b a n k s u c t io n t e n d s t o r e i n f o r c e t h ism o v e m e n t ( s h e e r t o p o r t) ; ( c ) s t e r n s o p p o s i te e a c h o th e r : s t e r n sy a w t o w a r d l o w w a t e r a t s te r n s b u t b a n k s u c t io n o p p o s e s t h i st e n d e n c y

The influence of depth of water on the channel width shouldnot be overlooked as a small underkeel clearance can have amarked effect on the vessel 's manoeuvrabili ty and can increasesignificantly the lane width required.Where bends are unavoidable in the approach channel , thechannel width must be increased at the bend to take in toaccount the extra area swept by the ship during the turningmovement . It has not been possible to formulate precise rulesfo r this increased w idth, but i t has been suggested that w here thechange of heading is of the order of 3 0 to 45, the chann el widthshould be increased by a t least twice th e largest vessel's beam.

ShelteredExample (m)L= 260B=40ExposedlocationExample (m)

ManoeuvringlaneAA = 2.0 x beam80

A = 2xbeam+ L sin 10124

BankclearanceBB = 1.5 x beam60

B= 1.5 x beam60

ShiftclearanceCC= 1.0 x beam40

C = L O x beam40

One-wayt r a f f i cwidthA + 2B20 0

A + 2 B24 4

Two-wayt r a f f i cwidth2A + 2B + C32 0

2A + 2B + C40 8

S t a r b o a r d

P o r t

S t a r b o a r d

P o r t

S t a r b o a r d

P o r tP o r t

S t a r b o a r d

S t a r b o a r d

P o r t Por tS t a r b o a r d

Channel

Channel

Channel


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26.3.L2 Channel depthThe depth of water available for shipping, whether natural orprovided by dredging, is dependent on the variations in waterlevel, the draught of the largest vessel, the change in salinity, thewave- and speed-induced vertical motion of the vessel and therequired underkeel clearance. Account may also have to betaken of the accuracy of soundings, the sediment depositedbetween dredging operations and the dredging tolerances. Theseare shown diagrammatically in Figure 26.6. Much research hasbeen carried out and recommendations published for minimumunderwater keel clearances,2 but i t is advisable fo r generalpurposes to provide a depth below low water level of 1.15 timesthe maximum draught of the vessel, with a minimum grossunderwater keel clearance of 1 m. Slightly greater clearancesshould be provided where the sea-bed is rock in order toincrease the clearance for safety of the ship against groundingon a hard surface.The depth alongside a berth can be slightly less than thechannel depth, and in some ports (generally small ones) withhigh tidal ranges, provision is sometimes made for vessels to siton the bottom during periods of low tide with access to the berthonly during certain periods of the tidal range.26.3.1.3 Turning circlesIt is normally desirable for a ship to be able to manoeuvrewithin a harbour and to leave the harbour bow first; a sufficientt u r n i n g area with the necessary depth of water must therefore beprovided. For a vessel to turn unassisted in one circular move-ment the diameter required is ideally 4 times the length of thevessel. With the assistance of tugs a turning circle with adiameter of twice the vessel's length is acceptable. Wheret u r n i n g dolphins or other mooring arrangements, which enablethe vessel to swing while partially moored, are provided, thisrequirement can be reduced fu r t he r .

26.4 Design of maritime structuresThe commonest types of maritime structures are:(1 ) Marginal berth (also termedquay or wharf). A berth parallel

to the shore and contiguous with it. Figure 26.7 shows atypical layout with three continuous marginal berths.(2 ) Pier. A finger projection f rom the shore on which berths areprovided (Figure 26.8).(3 ) Jetty. A structure providing a berth or berths at somedistance from the shore. It may be connected to the shore byan approach trestle or causeway, or the jetty may be of anisland type (Figure 26.9).(4) Dolphin. An isolated structure or strong point used formanoeuvring a vessel or to facilitate holding it in position atits berth (Figure 26.9).

(5) Roll-on roll-off ramp. A structure containing a fixed oradjustable ramp on to which a vessel's ramp is lowered topermit the passage of vehicles between vessel and shore(Figure 26.10).

26.5 Marginal berthsThese require a vertical face against which the ship berths and acontiguous working area alongside for cargo-handling equip-ment and cargo storage. The vertical wall can be achieved bytwo main methods: (1) a solid wall - which can be a gravity wallor a sheet-piled wall; (2) an open type - piled structure. Bothtypes are commonly used for marginal berths, the choicedepending primarily on depth of water, the foundation con-ditions, and the availability of suitable material for fillingbehind the solid wall. Typical designs ofquay wallsfor marginalberths are shown in Figure 26.11.

N o t e 1 N e t u n d e r k e e l c l e a r a n c e a n d w a v e r e s p o n s e a llo w a n c e c o n t rib u t e t o t h e m a n o e u v r a b i li t y m a r g inF i g u r e 2 6 . 6 F a c t o r s d e t e r m i n in g t h e r e q u i re d u n d e r k e e l c l e a r a n c e

D r e d g i n g e x e c u t io n t o l e r a n c e

Bot tomf a c t o r s

S h i p - r e l a t e df a c t o r s

W a t e r l e v e lf a c t o r sW a t e rR e f e r e n c eL e v e l

N o m i n a lC h a n n e l - b e dL e v e l

G r o s su n d e r k e e lc l e a r a n c e

C h a n n e lD r e d g e d L e v e l

S e l e c t e d Tidal L e v e lT i d a l c h a n g e duringt r a n s i t a n d m a n o e u v r i n gA l l o w a n c e f o r u n f a v o u r a b l em e t e o r o l o g i c a l c o n d i t i o n s

S t a t i c d r a u g h ti n s e a w a t e rA l l o w a n c e fo r s t a t ic d r a u g h t u n c e r t a in t ie sC h a n g e in w a t e r d e n s i t yS q u a t ( including d y n a m i c t r im) and d y n a m i c listW a v e r e s p o n s e a l l o w a n c e 1N e t u n d e r k e e i c l e a r a n c e 1A l l o w a n c e f o r b e d - l e v e l u n c e r t a i n t i e s( s o u n d i n g a n d sedimentat ion)A l l o w a n c e f o r bot tom c h a n g e s b e t w e e n d r e d g in g s


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S h e d S h e dQ u a y

R o R ob e r t hF i g u r e 26.7 M a r g i n a l b e r t h s

P i e r S h e d

F i g u r e 26.8 P i e r b e r t h s

B r e a s t i n gdolphinJet ty

M o o r i n gdolphin

F i g u r e 26.9 J e t t y b e r t h

F i g u r e 26.10 R o R o b e r t h S E C T I O N

S E C T I O N

S E C T I O N

S E C T I O N


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26.6 Piers and jetties26.6.1 PiersA pier normally requires a vertical face on both sides againstwhich ships ar e berthed, with th e deck of the pier providing th ew o r k i n g area fo r ca rgo han dl ing an d sometimes cargo storage.The methods o f cargo h and ling and s torage determine the wid thof the pier. If the pier is sufficiently wide, th e seaward end of thepier can also be used fo r berthing ships.As with marginal berths, the pier can be of a solid type or asuspended structure on piles. Because the pier extends into theseaway, part icular considerat ion needs to be given to i ts effecton the hyd raulic regime and l i t toral drift. The choice of whetherth e pier is solid or open will frequently depend on theseconsiderations, a l thou gh foun dat ion co ndi t ions and avai labi li tyof fi ll mater ia l m ay also affect th e choice . Typical layoutshowing clearances required between adjacent piers is shown inFigures 26.12 an d 26.13.

26.6.2 JettiesA je t ty is a s t ructure providing a ber th or ber ths a t somedistance f rom th e shore where th e required depth o f water isavailable. It consis ts norm ally of a je t ty head which provides theactual berth, which is connected to the shore by an approachtrestle or causeway.The jetty head sho uld n orm ally be aligned so that the vessel isberthed in the direction of the strongest currents, and is nor-mally an open-piled structure although a solid 'island'-types t ruc tu re is used occasion ally. The appro ach section is generallybui l t as an open-piled trestle type of structure mainly to avoidaffecting th e hydraulic regime, an d often also on grounds ofcost, although in shallow water a sol id causeway may becheaper. In some cases a causeway is used for the first section ofthe jetty approach from the shore , unt i l the depth of waterincreases to the point where a piled structure becomes moreeconomical . In de te rmining th i s poin t , the life an d m a i n t e n a n c ecosts of the open s truc tures need to be taken in to accou nt , as acauseway generally requires very little ma i n t e n a n c e .

Figure 26.11 T y p e s of quay walls, (a) Ancho red sheet pilewal l - s ing le t ie; (b ) anchored s h e e t pile w a l l - t w o ties; (c) s h e e tpile w all with relieving platform;


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F i g u r e 2 6 .1 3 C l e a r a n c e s f o r m u l t i- b e r t h p i e r s

The jetty head is normally smaller than the length of the shipit is designed to handle, and generally requires breasting dol-phins an d mooring dolphins (see sections 26.7.1 an d 26.7.2) fo rberthing and for maintain ing the vessel in position. In such casesth e jetty head need not be designed to resist berthing impactsand can be of a lighter construction, designed primarily fo rvertical loads. A typical oil jetty termin al is shown in Figure26.14.

26.7 DolphinsDolphins are of two kinds: (1 ) breasting dolphins; an d(2 ) moo ring dolphins. The use of both types is shown in Figure26.14. Turning dolphins ar e also used occasionally to assist inberthing vessels.

26.7.1 Breasting dolphinsA breast ing dolphin is an isolated structure designed to f u l f i ltw o dist inct f unc t ions : (1) i t must absorb th e kinet ic energy ofth e berthing vessel; and (2) i t must assist in restra ining th evessel at the berth. The opt imum disposi t ion of the breastingdolphins about the main service structure is critical to thedesign. Two berthing dolphins, one each side of the serviceplat form, are generally sufficient, but if the berth is to be used byships of widely varyin g size two additio nal do lphins closer to theplat form may be required. The face line of the dolphins inrelation to the f ron t of the service platform will depend on themaximum deflect ion of the dolphins. To prevent impactbetween the unprotected pla tform and the vessel , a gap mu st bemainta ined between them when the dolphins are a t maximumdeflection. The gap must not be so large as adversely to affectth e efficient operat ion of the cargo-handling equipment .There are two basic types of breasting dolphin: (1) rigid; and(2 ) flexible. The former will be either a massive structure (suchas a blockwork or caisson construct ion) or an open m ult iple-pi lestructure rigidly held together at the top by a massive deck or asteel jacket . Rigid s tructures s imply withstand the b er thing loadrelying on fenders to absorb the energy.The flexible dolp hin usual ly takes the form of parallel flexiblesteel tubes (o r a single tube), with a high elastic limit, whichabsorb most of the energy by deflection up to a m a x i m u m of 1.5to 2 . 0 m .The choice between a rigid or flexible dolphin will usua l ly bedetermined by the depth of water and the foundat ion con-di t ions.26.7.2 Mooring dolphinsMoo ring do lphins are isola ted s tructu res to which moo ring l inesar e attached to restrain th e ship at the berth. They are notnormally subject to impact f rom a berthing vessel and do nottherefore need fen derin g or to be flexible to abso rb en ergy. Theymust, however, be designed to resist the horizontal load f romthe mooring lines over a wide angular range, which arises fromboth wind and current load on the moored vessel and theranging of the vessel f rom wave act ion. They must a lso bedesigned fo r uplift , to resist th e vert ical component of the forcein the mooring line. They are normally rigid piled structures.

26.8 Roll-on roll-off berthsIn parts of the wo rld where tidal ranges are small, R o R o vesselscan berth, offload, an d load at any state of the tide, bridging th eship-to-shore gap with their own short ramps. Where tidalranges ar e large, R o R o vessels must either use impounded docksor more elaborate ship-to-shore ramps must be provided whichcan tolerate greater differences in level between ship and quay.Roll-on roll-off ramps can be of three types: (1) fixed at bothends; (2) fixed at one end - floating at ship end; and (3) comple-tely afloat .B u o y a n t R o R o ramps differ mainly f rom the i r nonbuoyantcounterpar ts in the way their seaward ends ar e supported. Theuplift of a submerged tank is used to carry th e dead load insteadof a convent ional br idge foundat ion. From this fundamentaldifference have arisen many characteristics in the structures o fbuoyant ferry ramps tha t are uniquely different from those ofconventional bridges; these may be seen in Figure 26.15.The basic design parameters, which include range of waterlevels, freeboard, quay level, an d limiting gradients, define th edimensions of the ramp with very lit tle scope for var ia t ion.The gradient of the ramp must allow vehicles an d cargo-handling plant to drive over it at all states of the t ide. Limitinggradients ar e usually dictated by the operators or ferry owners.

F i g u r e 2 6 . 1 2 C l e a r a n c e s f o r s i n g l e - b e r t h p i e r s

S = 2 6 + 3 O m

S = 3 b + 4 5 m


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Increased gradients allow shorter ramps with consequen t econo-mies of cost and a compromise must be struck. A maximumdeck gradient of 10% is desirable, bu t circumstances have ledto gradients of as high as 14% because th e most economicsolut ion may be not only to keep within th e desirable limit onthe most frequent t idal condi t ions, but also to allow steepergradients on relatively rare occasions.Considerable ingenuity is required to design ramps so tha tthey are compatible with the very wide range of geometriesadopted by ship designers. Harmonizing standards have beensuggested, but unification has not yet arrived.Roll-on roll-off terminals are dependent on being located inreasonably calm waters. In more exposed locations it can bevery difficult to ensure that the dyn amic wave-generated motionbetween a floating ramp an d ship will no t give rise to unaccep-table working condi t ions.

26.9 LoadsIn addi t ion to dead loads an d soil pressures, th e other forceswhich may act on maritime structures are: (1 ) those arisingfrom natural phenomena such as wind, snow, ice , temperaturevariations, currents, waves an d ear thquake; and (2) thoseimposed by operational activities such as berthing, mooring,cargo storage an d cargo handling. These loads may be groupedconvenient ly into th e fol lowin g general categories: (1 ) dead;(2) superimposed dead; (3) imposed; (4) soil and differentialwater; and (5) environmental .26.9.1 Dead loadDead load is defined as the effective weight of the materials an dparts of the structure that ar e structural e lements , excludingsoils, surfacing, fixed equipment an d tracks, etc. Fo r somedesign analyses i t may be preferable to consider th e weights o fthe elements in air and to treat separately the uplift forces due tohydrostatic pressures.26.9.2 Superimposed dead loadSuperimposed dead load is defined as the weight of all materialsforming loads on the structure that are not structural e lementsand wou ld include f i l l mater ia l on a re l ieving pla tform , surfac-ing, f ixed equipmen t for cargo handling, e tc .The effect of removing the super imposed dead load must beconsidered in any analysis, as it may dimini sh th e overallstability or d iminish the re l ieving effect on another par t of thestructure .26.9.3 Imposed loadImposed loads may be subdivided into:(1 ) Static and lon g-term cyclic.(2 ) Cyclic.(3) Impulsive.(4 ) Random.26.9.3.1 Static loadsLong-term cyclic loads ar e grouped with static loads where theyhave such long periods that they act on the structure as staticloads. The main imposed loads in this group are: (1 ) super im-posed live load covering cargo storage; (2 ) cargo handling an dt ranspor t systems equipmen t; (3) current loading; and (4) t imeaveraged w ind loading. Norm al m ethods o f s ta tic analysis maybe used to calculate the resulting stresses and movements fromth e imposed loads.

26.9.3.2 Cyclic loadsCyclic loads are those which repeat in all essential featu res afterregular intervals of t ime. The main cyclic loads are: (1 ) waveloading from regular trains o f waves; (2 ) vortex shedding fromcircular sections in steady currents; (3 ) vibrat ions from vehicu-la r traffic and tracked cranage; and (4) vibrating loads fromheavy, out-of-balance, rota t ing machinery fixed to the structure .26.9.3.3 Impulsive loadsThe main im pulsive loads are: (1) berthin g forces; (2) release orfailure of tensioned hawsers; (3) wave-slam forces on horizontals tructural members due to the passage of the wave profi lethrough the member; (4) crane snatch-loads when lifting cargof rom moving vessels; and (5) vehicular impact and breakingloads f rom cranes and road and rail traffic. The m ost s ignif icantof these is likely to be ber thing impact . Fender ing is no rmallyprovided to absorb th e energy of impact an d reduce th e load onthe structu re. The design of fen derin g is an in tegral part of thedesign of all structures subject to berthing impact and is dealtwith in section 26.10.26.9.3.4 Random loadsRandom loads va ry with t ime in a nonregula r manner . Themain random loads are: (1 ) normal wave loading; (2 ) loadingfrom wave- induced mot ion o f a moored vessel; (3 ) seismicloading; and (4) turbulent wind loading. Loading f rom wave-induced vessel m otio n is likely to be the most significant of theseloads in open-sea conditions. In some cases these loads can begreater than those due to ber thing, a l though they will a lways beless than b er thing loads with in a sheltered h arbo ur .Cyclic , impulsive and rando m loads are dyn amic in value anddynamic ana lys i s may be required to calcula te th e response o fth e s t ruc tures .3

26.9.4 Soil and differential water loadThese are the dominant loads affecting the s tabi l i ty of an ear th-re ta ining structure. The soil loads should be derived from th eproperties of the soil. The disturbing forces are affected by thesurcharge an d imposed loads on the retained soil26.9.5 Environmental loadsThese include th e effects of temperature, snow, ice, waves,current , t ide and t ime-averaged wind. The effects of the latterthree ar e generally con sidered to be long- term cycl ic loads an dar e grouped with static loads. The others can be cycl ic , rando mo r impulsive, according to the ir na ture .In most cases, th e impact live loads are the most important .Typical design loads are given in Table 26.3. It should be bornein mind tha t many cargoes cause point loads, e.g. corner loadsof con ta iners, an d also that c argo-handling plant can cause veryhigh wheel loads. These should be obtained f rom th e ma n u f a c -turers of the plant .

26.10 Fendering26.10.1 IntroductionFender systems ar e designed to protect both th e vessel and thebreast ing s tructure from damage caused by ber thing impacts .They range f rom t imber rubbing-str ips fixed to a quay face, topurpose-bui l t , free-standing energy-absorbing s tructures. Thefac tors determin ing the type and capaci ty o f a sui table fendersystem include the nature and size of the berthing vessels, the


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T a b l e 2 6 .3Load (kN/m 2)Light traffic 5General traffic 10General cargo 20Containers:empty, 4-high 152-high stacked 20

4-high stacked 30RoRo cargo 30-50Multipurpose 50Offshore supply base 50-150Paper 55Forest products 70Steel products 80Coal 100-200O re 100-300

form of the s tructure to be protected, the environmental con-ditions (i.e. wind, waves, currents etc.,) the operational require-ments and the consequences of damage to the vessel or struc-ture .The berthing force is often the predominant lateral loadimposed on a quay or jetty structure and its effect is largelycontrolled by the fender system adopted. The design of thefendering system must therefore form an integral part of thestructural design. The selection of the fendering system willoften be the first step in the design process and can in fluence theshape, size and form of structure.A fendering system may be defined as a structural element ora combination of elements which ensures the safe disposition ofa vessel's kinetic energy whilst i t berths in a con trolled man ner.Most systems incorporate an elastic energy-absorbing unit butoccasionally a plastic or friable unit is also included, thedeformat ion of which provides addi t ional protect ion againstmarginal overloading.26.10.2 Fendering systemsFendering systems may be divided into two main categories:(1 ) Detached systems^ in which the berthing forces do not act onth e main quay o r je t ty s t ructure .(2) Attached systems, in which the fend er elements are attachedto the main quay o r jetty structure. The structure thenprovides the reactive force.It will generally be found that when the operat ional , environ-mental and structural design parameters have been examined itis clear which category sho uld be adopted.26.10.2.1 Detached fender systemsThe category of detached systems may be subdivided into;(1 ) detached quay fender systems; and (2) breasting dolphins.The main advantage o f a detached system is that it permits alighter main structure to be designed. Also, where th e capacityof an existing berth is to be upg raded, a detached fend er systemmay be used to advantage if the existing structures haveinsufficient strength to withstand the increased berthing loads.A common example of a detached fender system is a row offree-standing piles (usually steel or timber) driven into the sea-or river-bed in f r on t of the face of the main s tructure . Ber thingenergy is absorbed mainly by deflect ion, th e capacity fo r energyabsorption being determined by the size, length, penetration andmaterial properties.

Breasting do lphins ar e berthing structures independent of theservice structureprovided for the vessel. Their disposition aboutth e service quay or jetty head is such as to effect th e mostsuitable compromise for the range of vessels envisaged. Withflexible dolphins th e energy absorption is provided in part bydeflection of the entire structure and in part by energy-absorb-ing uni ts attached to the dolphin face. With a rigid dolphin, al lth e energy dissipation is achieved by units similar to those usedin attached fender systems.26.10.2.2 Attached fender systemsAn attached fender system normally consists of energy-absorb-in g units bolted to, or suspended from, a quay face or strongpoints o n a jetty. Some types o f energy-absorbing uni ts ar eillustrated in Figure 26.16. Most of the uni ts are made fromsynthetic rubber and the required energy absorption capacity isachieved by deformation in compression or shear. Some types,such as the hollow cylindrical rubber fenders, th e arch type, an dpneumatic fenders, can be allowed to make direct contact withth e vessel's hull whereas others, such as Hidac, Raykin an d celltypes requ ire face panels to reduce th e contact pressure. The sizeof the face panel is determined by the permissible hull pressure.Typical attached fender systems are shown in Figure 26.16.Gravi ty fenders are those in which k inet ic energy is conver tedto potential energy by means of raising a large mass. Theyrelieve the main s tructure of the ber thing load but imposeconsiderable dead load and a horizontal fo rce depending on themovement of the fender block. The ber thing beam pr inciplecombines the absorption capacities of cantilevered piles andgravity systems whils t avoiding the dead-load penalty of thelatter.26.10.3 Design of an attached fendering systemThe design of an attached system must be integrated with th edesign o f the structu re to which it is attached and comprises:(1 ) Calculation of energy to be absorbed.(2 ) Investigation of alternative systems capable of absorption.(3) The energy, and calculations of force (see sections 26.10.4and 26.10.4.2 below), to be resisted by the structure fo r eachalternative.(4) Investigation of design o f structu re to resist force ofber thing.(5 ) Selection of fender system and structure.In both cases, th e calculation of energy to be absorbed is criticalto the design.26.10.4 The basic energy equationThe most generally accepted form of expressing the kineticenergy of a berthing vessel available for absorption by a fendersystem is:

E= 0.5Mv2 C EC M C SQ (26.2)where E is the kinetic energy available for dissipation by thefender system, M is the mass of vessel (displacement to nn age), vis th e veloci ty of vessel norma l to fender at p o i n t of impac t , CE isth e eccent r i c i ty fac tor , CM is the mass factor (coefficient o fh y d r o d y n a m i c mass), Cs is the softness coefficient (stiffnessfactor) an d Cc is the ber th conf igura t ion coefficient.26.10.4.1 Design velocityAs the energy var ies with th e square of the veloci ty of the


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F i g u r e 2 6 . 1 6 T y p i c a l r e p l a c e a b l e e n e r g y - a b s o r b i n g u n i t sapproaching vessel, the choice of the design velocity is mostcr it ical . I t is , however, un for tu nately , one of the m ost subject ivechoices in the design o f mari t ime structures, depending as itdoes on: (1) ship size, type and frequency of arrival; (2) pos-sible constraints on the ship's movement approaching berth;(3 ) wave condi t ions likely to be encountered a t ber thing;(4 ) current condi t ions likely to be encountered a t ber thing;(5 ) wind condi t ions likely to be encou ntered a t ber thing; (6) theuse o f tugs; and (7) whether or no t speed-of-approach measur-in g equipment is fitted an d used.Figures suggested in BS 6349' are given in Table 26.4. TheseT a b l e 2 6 . 4Displacement Transverse velocity(t ) (m/s)Up to 2000 0.302000-10000 0.1810000-125000 0.16Over 125 000 0.14

figures m ay however need to be modified as necessary toaccommoda te th e local factors .26.10.4.2 Eccentricity factor C EWhen a berthing vessel m akes in i t ial contac t at a poin t r emotefrom it s centre of gravi ty, par t of the energy is dissipated by theensuing ro ta t ion . The consequent reduct ion in required energyabsorpt ion capaci ty in the fender is obta ined by apply ing th eeccentricity factor C E. The eccentric i ty factor is no rmally calcu-lated from Equat ion (26.3) below:

K 2C*=lCTW (26-3)where K is the radius of gyrat ion of the ship (generally between0.2L an d 0.25L where L is the length of the vessel) and R is thedistance of the p o i n t o f impac t from th e centre of gravi ty of thevessel.26.10.4.3 Mass factor C MThe mass factor CM takes account of the mass of water


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entrained with the moving vessel. This is commonly referred toas the ' hydrodynamic mass'. The sum of the 'hydrodynamicmass' and the displacement gives th e 'vi r tual mass ' of the vessel.The mass factor CM is the ratio of the virtual mass to thedisplacement . Many a t tempts have been made to define th ehydrodynamic mass mathematically but n o n e ha s been particu-larly successful. A value of 1.3 is generally used fo r C M .Al ternat ively, th e fol lowing simple relation ship based on experi-mental results may be used:Q1=I+^ (26-4)D

where D is the vessel's draught and B is the vessel's beam.26.10.4.4 Softness c o e f f i c i e n t C8The softness coefficient allows for the por t ion of the impac tenergy tha t is absorbed by the ship's hull. Little research intoenergy absorpt ion by ships' hulls has taken place, but it has beengenerally accepted that the value of C8 lies between 0.9 and 1.0.In the absence of mo re rel iable inf orm ation a figure of 1.0 for C8is recommended when a soft fendering system is used, an dbetween 0.9 and 1.0 for a hard fendering system.26.10.4.5 Berth configuration c o e f f i c i e n t C fThe ber th configurat ion coefficient allows for that por t ion of theship's energy which is absorbed by the cu shioning effect of watertrapped between th e ship's hull an d quay w all. The value of Cc isinfluenced by the type of quay construct ion and i ts dis tancefrom the side of the vessel, the berth ing ang le, the shape o f thehull and its un derkeel clearance. A valu e of 1.0 for Cc should beused fo r pi led je t ty s t ructures, and a value fo r Cc of between 0.8an d 1.0 is recommended for use with a solid quay wall.26.10.5 The factor of safetyTwo levels of energy of impact - ' normal ' and 'abnormal' -shou ld be established for the design of the fen der system and thesupport ing ber th s tructure .The ber thing energy as computed in accordance with th eabove formula is based on normal operat ions and may beexceeded for accidental occurrences such as: (1 ) engine failureof ship or tug; (2) breaking of mooring or towing l ines; (3) sud-de n changes o f wind o r cur rent condi t ions ; and (4) h u ma nerror . To provide a margin of safety against such unquant i f iablerisks i t is recommended that the ultimate capacity of the fendersshould be double that calcula ted for normal impacts .Because of the nonlinear energy/react ion/deflect ion charac-teristics of most fender systems, the effects of both normal andabnormal impacts on the fender system and ber th s tructuresshould be examined.26.10.6 Structural considerationsThe type of structure to which the fender system is attached isusually dicta ted by foundat ion condi t ions.In si tuat ions w here gravi ty s tructures such as blockw ork wallsor caissons are the economical solution it is unlikely that th eoverall design will be very sensitive to the berthing load, thoughmore detailed factors such as the location of a service ductbehind the berthing face or stability of the capping block, maybe affected.Where a piled structure is used, th e ber thing force m ay dictatethe pile layou t. Where a piled structure supports cargo-handlingequipment or pipework, unacceptable deflection of the structurerather than overstressing is often found to be the l imit ingcriterion.

In the design of fender support systems it is important that arobust means of restraint is provided against forces acting alongthe berth face. These fo rces are produced by frictio n between thehull and the fender and can reach 50% of the maximum fenderreaction.Con siderat ion mu st also be given to the structural constra intsimposed on the fender designs by the form of construct ion of theberthing vessel. Berthing loads ar e generally n o t considered as abasic design criterion by naval architects.26.11 LocksMarit ime locks ar e used to allow vessels to pass between tidalwaters and an impounded water area which can be a dock,ha rbour or ship canal, an d enables th e impou nded water area tobe maintained at a constant level, eliminating tidal effects.In a port that has a large tidal range, locks may be essential toprevent vessels grounding while alongside berths. A cons tan twater level behind a lock also ha s advantages in tha t th e heightof quays depends only on the ship's draught and no accountneed be taken of t ides upstream of the lock. Loading an ddischarging is also simplified with a constant water level, andnormally waves an d currents can be disregarded.26.11.1 Lock dimensionsThe usable length of the lock chamber and the width an d depthof th e sill should be sufficient to ensure that all vessels enteringthe dock m ay be safely locked in and out. The level of the outersill is normally dependent upon the dimension of the approachchannel; the level of the inner sill is dependent upo n theimpounded water level and the maximum vessel draught . Nor-mally a safety margin of 1 m is provided between th e ship keeland the sill. A clearance of 10% of the maximum ship beamshould be allowed on each side of the vessel. In determining th elength of a lock it should be borne in mind tha t two to s ix tugsf rom 25 to 35 m in length may be required depen ding o n the sizeof the ship and the ship's own m anoeu vrabil i ty . Approximately1 0 m addit ional length is required fo r towlines. The length an dwidth of the lock also depends on the number of ships beinglocked s imultaneously.26.11.2 Lock gatesLock gates can be caissons, mitre gates or sector gates. Fo rsmaller locks, single leaf gates (vertical or horizontal axis) ar esometimes used, bu t these are less common.Mitre gates are probably the most com mon type of gates forlocks under 3 0 m wide, as they are generally more economicalthan other types, mainly because of the less extensive structu ralwork required to house them in the lock heads, bu t also becausein general terms they can be more easily handled for mainten-ance. Mitre gates obtain their strength largely f rom the head ofwater on one s ide holding them together . However , they haveth e disadvantage that they can on ly resist a head of water in onedirection. They are not suitable when th e t ide level outside th elock rises above the impounded level, although it is sometimesfound that in such a case it is cheaper to provide an addition alpair of mitre gates rather than to use other types. Mitre gatesalso have th e disadvantage that they ar e likely to vibrate wherethere is only a small hydraulic head holding them together. Insmaller locks, such as those in marin as, i t is generally fo un d th atradial sector gates o r delta gates are the most suitable.

26.12 PavementsPavements in por t areas wh ich ar e used by cargo-handling plant


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ar e generally subjected to much higher loads an d much greaterrepeti t ion o f loading than normal road pavements. They ar ealso susceptible to damage from th e plant itself, e.g. th e l ift ingprongs attached to fork-lift t rucks . The bearing capacity of thesubsoil determines th e pavement design to a large extent.Surfacing used for pavements can be either:(1 ) Flexible: asphalt - normally expensive concrete blocks -easily maintained.(2 ) Rigid: concrete - subject to cracking under h igh concen-trated loads. Precast concrete rafts - if settlement occursthey can be l ifted, th e ground made up to level, and the raf tsrealigned.The design of heavy-duty pavements is st i ll semi-empirical. TheBritish Ports Association has produced a m a n u a l of designcharts4 suitable for the design o f pavements fo r cargo-handlingplant curren t ly in use wi th a wide range of soil condi t ions .Fo r low-cost storage areas fo r containers , gravel surfac ingshave been used in some ports.5Grades an d consequent drainage pat terns should avoid ex -cessive an d frequent peaks an d valleys. Large open expanseswithou t grade breaks ar e needed fo r ground s tacking. Pavementslopes should be held at 1 to 1 .5 % maximum.

26.13 Durability and maintenanceIt is well known that the marine environment i s one of the mostsevere as far as deterioration of materials is concerned. Inaddi t ion to th is, durab i l i ty can be dras t ically affected by thelocation of the structure. Some of the factors affecting durabi l i tyare:(1) Temperature of the sea.(2 ) A ir pollut ion. It has been found , fo r example, that th e rate

of corros ion of galvanized s teel can vary by a fac tor of 10:1in different parts of the UK due to a ir pollutants .(3) Pol lut ion of the sea. This is somet imes dependent on the useof th e berth, e.g. at a fertilizer terminal, where chemicalc ompounds can f ind their w ay in to th e sea, and the rate o fcorros ion is much higher than in un polluted sea water.The fac tors affecting durab i l i ty and repairs of reinforced con-crete in the marine env i ronment are well docum ented else-where5- 6 but marine s t ruc tures should be robust , avoiding th insections an d wi th a minim um c over to reinforcement o f 5 0 mm.For greater protection against corrosion, galvanized or coatedsteel may be used o r cathodic protection applied to the reinfor-cement .

The part of a structure most susceptible to corrosion ordeterioration is the area in the t idal zone o r splash zone, an dspecial consideration needs to be given to this area. With steelpiles, concrete muffs are frequent ly provided fro m the un ders ideof th e concrete deck to just below low-water level; steel sheetpiling is frequ ently encased in concrete from cope level to belowlow-water level.Durabi l i ty is normally considered at the design stage, butmaintenance has an equal ly important effect on the life ofstructures, and should also be considered at the design stage.There are two kinds o f maintenance: (1 ) preventive; an d(2 ) remedial. Methods of both types o f maintenance are wellk n o w n . The principal preventative methods are protective coat-ings andcathodic product ion - both need to be considered andincorpo rated w here appropriate at the design stage. From thedesigner's point o f view it is impor tan t also to recognize how

the provis ion of maintenance procedures . I f the maintenancemethods ar e s t raight forward they are far more likely to becarried out than if access is difficult , or if com plicated plan t orequipment i s required.

References1 Brit ish S t a n d a r d s In s t i tu t io n (1984-1985) Code of practice fo rmaritime structures. BS 6349 Parts 1, 2 and 4. BSI, M i l t o n Keynes .2 P e r m a n e n t I n t e r n a t i o n a l A s so c i a ti o n of Navigat ional Congresses(1985) Underkeel clearance for large ships in maritime fairways withhard bottoms. P I A N C S u p p l em e n t to Bullet in N o . 51 .3 C o n s t r u c t i o n I n d u s t r y Research an d I n f o r m a t i o n A s s o c i at i o n (1977)Dynamics of marine structures. M ethods of calculating th e dynamicresponse of fixed structures subject to wave and current action.CIRIA Repor t No. UR8 U nderw ater Engineer ing Grou p,L o n d o n .4 Brit ish Ports Associat ion (1982) Th e structural design of heavy-dutypavements fo r ports an d other industries. B P A , L o n d o n .5 I n s t i t u t i o n o f Civil Engineers (1986) Maritime an d o f f s h o r e structuremaintenance. Thomas Tel ford, London.6 C o n s t r u c t i o n In du s t ry Research an d I n f o r m a t i o n A s s o c i at io n (1986)Influence of methods and materials on the durability of repairs toconcrete coastal an d o f f s h o r e structures. UEG P u b l i ca t i o n No.

U R 3 6 , U n d e r w a t e r E n g i n e e r i n g G r o u p , C I R I A , L o n d o n .Bibl iographyAmer ican Associa t ion of Por t A utho r i t i es (n .d . ) , Port designs an dconstruction, A A P A , W a s h in g t o n , D.C.Amer ican I ron an d Steel I ns t i t u t ion ( 1981) Handbook o f corrosionprotection fo r steel pile structures in marine environments. A I S I ,W a s h i n g t o n , D.C.Amer ican Society of Civil Engineers (1974) Port s tructure costs: areport by the task committee on port s tructure costs, C o m m i t t e e onPor t s and Harbo urs , ASCE Waterway s , Harbo urs and Co as talEngineer ing D i v i s i o n , N ew Y o r k .Cor n ick , H. F . Dock am i harbour engineering. Charles Griffin , L o n d o n .Depar tment of Transpor t (1982) Ship behaviour in ports an d theirapproaches. H M S O , L o n d o n .Fuhrer, M. and Romisch, K. (1983) Co nt r ibu t ion to the design offenders an d dolphins . 8t h International Harbour conference,Antwerp.Gulf Pu bl i sh in g C o m p a n y ( n . d .) Port engineering. GPC, Hous ton.M in is t ry o f Transpor t , Japan (1980) Technica l s tandards fo r ports an dh a r b o u r facilities in Japan. Bureau o f Ports an d Harbours .N a t i o n a l Por t s Coun ci l (1920) Port structures-an analysis of costs an ddesigns of quay walls, locks and transit sheds. N P C , L o n d o n .Nat iona l Por t s Coun ci l (1978) Containers ~ their handling an d transport.A survey of current practice. N P C , L o n d o n .Permanent Inte rna t ion a l Associa tion o f Naviga t ion a l Congresses(1978) Standardization of ro-ro ship an d berth. I n t e r n a t io n a l S t u d yCommission Repor t , P IANC, Geneva .Permanent Inte rna t ion a l Associa t ion of Naviga t iona l Congresses(1985) Port m aintenance handbook. Supplement to Bullet in No. 50,PIANC, Geneva .Permanent In te rna t io na l Associa t ion of N aviga t iona l Congresses(1987) Final report of the International Com mission for the Study o fLocks. Supplemen t to Bullet in No. 55, PIAN C, G eneva.P e r m a n e n t In te rn a t ion a l Associa t ion o f Naviga t io na l Congresses(1987) Development of modern marine terminals. S u p p l e m e n t toBulletin No. 56, PIAN C, Geneva .Recommendations of the Committee fo r Waterfront Structures (1982)4th English edi t ion ( t ranslated from the 6th German Edi t ion) .S o h n .United Nat ion s (1985) Port development - a handbook for planners indeveloping countries. UN, New York.US A r m y C o r p of Engineers (1974) Small craft harbours; designconstruction and operation, Coastal En gineering Research Center,Special Report No. 2.Vrijer, A. (1983) 'Fender forces caused by ship impacts ' . 8t h

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