Criteria for (un)-loading Container ships

Document title Criteria for (un)-loading Container shipsAuthor G-J Goedhart

Status Final Report

Date 19 September 2002

Criteria for (un)-loading Container ships 2 October 2002i

PREFACE

As last step in the process of becoming a master of science a research project isexecuted. This project comprehends a study into the criteria for (un)-loadingcontainerships. The research project is supervised by a research committee that consistsof the following people:

Prof ir H. Ligteringen Faculty of Civil Engineering and Geosciences Chairman

Prof ir J. Rijsenbrij Faculty of Mechanical Engineering and Marine Technology

Ir. R. Groenveld Faculty of Civil Engineering and Geosciences

Ir. J.C. van der Lem Royal Haskoning

This research project has been carried out at Royal Haskoning, Rotterdam

Criteria for (un)-loading Container ships 2 October 2002ii

SUMMARY

Time matters in the world of container shipping. Every shipping company focuses onmaximizing the use of its ships. This means maximizing the sailing hours and thusreducing the hours spent in ports

For this reason shipping companies demand a turnover time of less than twenty fourhours from the transshipment company. During these twenty four hours containers arelifted off and later on the ship. To meet the imposed time requirements it is of importancethat ship motions are reduced to a minimum since the tolerances for placing containersare quite narrow.

When designing a new container terminal it is necessary to know how much shipmovement is allowable under normal conditions. The allowable ship motion determinesthe amount of protection that is needed for the berth. This research project has beeninitiated to determine improved “criteria for (un)-loading containerships”. Beside thesecriteria the focus has been on establishing a relation between the handling rates and themotions of the vessel that is (un)-loaded.

First a literature study has been undertaken. In this literature study five related papersare discussed and compared to each other. By comparing the papers it was possible tofind a new approach to the subject.

The new approach has been found in research done by Slinn (1979), in 1979. He placeda steel frame on a quay that could be given a sine shaped motion. The frame representsthe cell guides and the motions represent ship motions. He then asked a number ofcrane operators to participate in the test. The crane drivers were asked to place acontainer in the moving cell guides. During these tests Slinn gave the frame a certainamplitude and period and noted the number of attempts a crane driver needed to place acontainer into the frame.

Furthermore he observed the steps taken by the crane drivers to place a container in thecell guides. He found out that crane drivers have no interest in following the moving cellguide but that they simply waited for the cell guide to pass under the container.

Based on these two results from Slinn a model has been developed that calculates thereduced handling rates in case of increased ship motion. Full details of the model can befound in chapter 4.

Furthermore a questionnaire has been sent out to verify the opinions of harbourmasters.Unfortunately the response was so disappointing that the questionnaire could not beused for scientific purposes.

From this research project the conclusion is drawn that the criteria as proposed byPIANC are not strict enough. For undisturbed handling rates the maximum surge motionneeds to be limited to 0.3 m (peak to peak) and for sway the criteria should be 0.2 m(peak to peak). Furthermore the reduction of the handling rates depends on the period ofmotion.

Criteria for (un)-loading Container ships 2 October 2002iii

TABLE OF CONTENTSPage

PREFACE I

SUMMARY II

1 INTRODUCTION 1

2 TECHNICAL BACKGROUND AND PROBLEM ANALYSIS 22.1 Situation description 22.1.1 Containers 22.1.2 Container ships 32.1.3 Cranes 42.1.4 Mooring 62.1.5 Ship motion 72.1.6 Co-ordinate systems 82.2 Problem definition 92.3 Objective 102.4 Starting points 102.5 Assumptions 11

3 LITERATURE STUDY 123.1 Introduction 123.2 Previous conducted research 123.2.1 P.R.C. Harris 123.2.2 Port and Harbour Research Institute (PHRI) 133.2.3 Nordic Countries 153.2.4 PIANC 163.2.5 Hessenatie, d’Hondt 203.3 Similarities 203.3.1 Influence mooring system 203.3.2 (un)-loading equipment 213.3.3 Crane operator 213.3.4 Literature study 223.4 Differences 223.4.1 Acceptable downtime 223.4.2 Criteria 223.4.3 Relation rotation-translation 233.4.4 Cell Guides 233.4.5 Field measurements 243.5 Shortcomings 253.5.1 Period of motion 253.5.2 Relation throughput- ship motion 253.5.3 The human factor 253.5.4 Rotation criteria 273.5.5 Should criteria be uniformly interpreted? 273.6 Conclusions 283.7 Recommendations 28

Criteria for (un)-loading Container ships 2 October 2002iv

4 MODELLING 294.1 The model 294.1.1 Training module 294.1.2 Operations module 314.2 Calibration 354.3 Runs 374.3.1 Results 384.3.2 Comparison with PIANC 404.4 Application of the model 414.5 Possible improvements 424.6 Conclusion & Recommendations 434.6.1 Conclusions 434.6.2 Recommendations 43

5 QUESTIONNAIRE 445.1 Questionnaire 445.2 Group of interest 465.3 Results 46

6 CONCLUSIONS AND RECOMMENDATIONS 48

7 REFERENCES 50

List of appendices

Appendix 1: Research Assignment ...............................................................52Appendix 2: Program Listing.........................................................................53Appendix 3: Returned Questionnaires ...........................................................61Appendix 4: Addresses of the questionnaire ..................................................67

List of tables

Table 1: Overview container dimensions......................................................................2Table 2: Container ship sizes ......................................................................................3Table 3: PIANC criteria for container vessels..............................................................10Table 4: Harris criteria ..............................................................................................13Table 5: Nordic criteria..............................................................................................16Table 6: PIANC criteria for containerships..................................................................20Table 7: Calibration Points ........................................................................................36Table 8: Calibration uncertainty factor........................................................................37Table 9: Reduced handling rates...............................................................................38Table 10: Reduced handling rates for pure surge .......................................................39

Criteria for (un)-loading Container ships 2 October 2002v

List of figures

Figure 1 High-Low cell guide entrance .........................................................................4Figure 2: A twin spreader lifting two 20-ft containers .....................................................5Figure 3: Portainer size and growth at ECT..................................................................5Figure 4: Degrees of freedom for a container ...............................................................6Figure 5: Mooring arrangements..................................................................................7Figure 6: Ship motion..................................................................................................7Figure 7: Co-ordinate system ......................................................................................8Figure 8: Wharf efficiency scheme. ............................................................................14Figure 9: Field measurements of moored ship movements..........................................19Figure 10: Model definition........................................................................................30Figure 11: Example training results............................................................................31Figure 12: Definition of decision square .....................................................................32Figure 13: Model framework .....................................................................................34Figure 14: Graph Slinn..............................................................................................35Figure 15: Calibration graph Slinn..............................................................................36Figure 16: Relation period vs. handling rates..............................................................40Figure 17: Loading sequence ....................................................................................42

Criteria for (un)-loading Container ships 2 October 20021

1 INTRODUCTION

After World War II world trade increased rapidly and with it the sea transportationvolumes, which lead to long waiting times and serious congestion in the ports. In theearly 1950’s MacLean Trucking, later Sea-Land, and Matson Navigation Companystarted with the first containerised transports along the East and West Coast of the USAas a purely domestic operation. The early period was characterised by troubles withoperational systems, stacking and handling equipment, as well as with informationexchange and management in this new, capital-intensive branch of port activity. Thecontainer seemed to be the ultimate solution to this problem. Since there was asimultaneous development by transport companies (sea, road, and railway) on the onehand and by terminal operators on the other hand, different approaches with respect tothe set-up of container terminals gained support. Soon, the containerised transportstarted spreading from the domestic US transport scene to the international maritimetransport market, first on some Atlantic trade routes, with the Pacific routes followingsoon. Some countries or regions have long resisted the arrival of containers in their ports-South Africa, South America and in particular Brazil- but ultimately had to give in. In 30to 40 years time world container trade has increased spectacularly as well as the size ofthe ships and terminals.

The growth of the ship sizes leads to higher required (un)-loading rates since shippinglines want to take full advantage of their ships. One way of fully optimising the use of aship is to reduce the time spend in a harbour. Thus a short turn-around time, generallyless than 24 hours, is demanded. In order to achieve such short times it is essential thatthe ship movements be kept to a minimum since the movement of moored ships has alarge influence on the efficiency of the (un)-loading process.

The goal of this study is to determine limits for allowable ship motions so that the (un)-loading operations of containerships are not hampered. And if possible establish arelation between ship motion and handling rates.


2 TECHNICAL BACKGROUND AND PROBLEM ANALYSIS

2.1 Situation description

In the transport chain of containers there are many different phases. For this researchproject the only phase that is important is the loading and unloading phase. How thecontainer gets to the quay is not relevant nor is it relevant how the container leaves thequay after being unloaded from the containership.

During the loading and unloading phase there are three elements that play a role. Firstthere is the container itself, second there is the ship the container is placed on and thethird one is the crane that transports the container from the quay to the ship. Two otherimportant aspects are the mooring system and the motion of a moored ship. First thesefive items will be discussed.

2.1.1 Containers

A container is a steel or aluminium box used for the transport of general cargo and breakbulk. Putting break bulk in a container eases the handling of break bulk. Containers arefitted with corner castings that serve as grips for the handling equipment. The firstcontainers had dimensions of 8 ft x 8 ft x 33 ft. (2.44 x 2.44 x 10 m). Nowadays mostcontainers are either 20 ft or 40 ft long. The capacity of container vessels is expressed inTwenty Feet Equivalent Units, or TEU. Besides these two ISO container sizes thereexists a wide variety of non-ISO sized containers (see Table 1).

Type External dimensions (feet) Maximum payload (kg)L B H

ISO 1a 40 8 8 or 8’6” 30.480 1b 30 8 8 or 8’6” 25.400 1c 20 8 8 or 8’6” 24.000 1d 10 8 8 or 8’6” 10.160Non-ISO 20 8’6” 9’6”

40 8’6” 9’6”45 8’6” 9’6”48 8’6” 9’6”53 8’6” 9’6”20 8’2½” 8’6”Bell40 8’2½” 8’6”

Table 1: Overview container dimensions

Apart from the variation in size there is a range of special purpose containers, both ISOand non-ISO, including the following:

- Refrigerated containers or reefers, requiring electrical supply points both on the shipand on the terminal.

- Tank containers, open frames of mostly TEU size around a tank. In case of hazardouscontents these containers are separated from the rest in the storage yard


- Flats, in fact just a bottom structure with corner castings used for large pieces of cargothat cannot be placed inside a box, but comply with the size and payload requirements.

- And many other odd size and shapes.

2.1.2 Container ships

The first generation container vessels were general cargo vessels that were adapted tocarry containers. Since then several classes of container vessels have been introducedwith increasing dimensions and capacity. See Table 2.

Class TUE capacity DWT (average) Length (m) Draft (m) Beam (m)1st generation 750-1100 14,000 180-200 9 272nd generation 1500-1800 30,000 225-240 11.5 303rd generation 2400-3000 45,000 275-300 12.5 324th generation 4000-4500 57,000 290-310 12.5 32.3Post Panamax 4300-4600 54,000 270-300 12 38-40Jumbo >6000 80,000 310-350 14 42.8

Table 2: Container ship sizes

Container vessels are fitted with cell guides to place and hold the containers below deck.Hatches cover the holds. On these hatches the containers are stowed in rows parallel tothe ship axes and up to 7-high. Twist locks and lashings secure the containers to thedeck and to each other.

The tolerances for the cell guides are very small. The classification societies accept thefollowing tolerances in the cell guides position in a containership:

Longitudinal: cell length = container length + 36 mmTransversal: cell width = container width + 25 mm

To ease the entrance of containers into the cell guides there are two types of guidancesystems. The first system has a funnel placed at the upper side of the guides called aleading edge. The leading edge tolerances are larger, e.g. 240 mm longitudinally and220 mm transversally. The second system has an alternating high-low cell guideentrance, see Figure 1, which should ease the positioning of a container.


Figure 1 High-Low cell guide entrance

New in container vessel design were the hatchcoverless vessels with full height cellguides, which can be stacked 4 high above deck. A nickname for these ships is “theporcupine”. The elimination of time for lifting off and putting on the hatches and removingand placing the lashes and twist locks justifies the use of hatchcoverless vessels. Anegative effect of this design is the fact that tropical rain showers can freely enter theholds. This requires extra pumps in the holds to pump the rainwater overboard.Furthermore overcoming seawater can easily enter the holds. To reduce the entrance ofseawater in the hold these ships are fitted with a higher freeboard. A higher freeboardleads to a higher GRT, and since the fees the ship has to pay for port entry and canalpassage are based upon the GRT this design does not get a broad follow-up. Even P&ONedlloyd who first implemented the design did not order the latest ships according to thisdesign.

2.1.3 Cranes

For (un) loading containerships ship-to-shore gantry cranes, or portainers, are used.These cranes are generally rail mounted, although recently mobile cranes have beenintroduced again. The cranes are characterised by a boom, which can be lifted or pulledinward. The cranes are provided with a trolley and a cabin, which moves with it, fromwhich the crane driver guides the trolley and the spreader to the right cell on the ship.

A spreader is a rectangular steel frame equipped with a twistlock on each corner. If thespreader is placed on top of a container these twistlocks enter the top corner casting ofthe container. If all four twistlocks correctly entered the four top corner castings thetwistlocks are activated and the container and spreader are connected. At this point thecontainer can be transported to a desired location. To facilitate the pick-up of a containerthe spreader is equipped with four hydraulic flippers. These flippers can be operated inrandom pairs or all at the same time. The flippers allow an offset of 150 mm from thecentre line of the spreader to the centre line of the container. Furthermore there arespreaders with telescopic beams that enable the crane driver to adjust the spreader sizeto the container size and twin spreaders that can carry two twenty foot containers or one

High

Low

High

Cell Guides


forty foot container. Another important feature that is placed on all corners of thespreader is a guide wheel or low friction strip of iron. This feature is meant to reduce thefriction between the spreader and container when travelling up or down the cell guides.

Figure 2: A twin spreader lifting two 20-ft containers

The container is picked up and transported to the space between the seaward and thelandward leg of the crane. From this point on it is transported to the storage area where itis stacked until further need.

Some typical properties of the crane are:Lifting capacity: Around 60 tons under the spreader.

Approximately 75 tons on the ropes.Boom length: up to 65 m for the largest vessels.Rail gauge: varying from 15 to 35 m.Crane productivity: Peak: 40-50 moves per hour.

Average: 20-30 moves per hour.

Figure 3: Portainer size and growth at ECT


For effective loading and unloading it is essential that the movements of the ship and thecrane are kept a minimum. So the ship has to be moored tight to the quay to reduce itsmovements. Due to uneven loading of the vessel it is possible that the ship lists to oneside. List can be seen as a steady state. In order to prevent damage to the quay and thecrane a maximum list angle of 5-degrees is allowed.

The container in the spreader has six degrees of freedom of movement, threetranslations (X, Y and Z) and three rotations (skew, trim and list). In addition there is thesway angle γ between the lifting cables and the vertical. See Figure 4 for their definitions.Sway is induced by the transport of the container from the quay to the ship or vice versawhen the container is exposed to accelerations and decelerations. The translations arenecessary movements for loading and unloading operations. The sway angle is causedby the inertia of the container and is unavoidable but can be kept under control by anexperienced crane operator. Skew, list and trim are caused by uneven loaded containersand greatly delay the positioning of a container on an Automated Guides Vehicle (AVG)or in the cell guides. Currently anti-skew devices are being developed but it will probablytake a while before these control mechanisms are common use.

Figure 4: Degrees of freedom for a container

Movements of the container in the spreader greatly influence the efficiency of the (un)-loading process. Because of low friction the damping of motion is relatively slow, whichimplies long waiting times before a container can be placed on the desired location.Especial skew and list make it more difficult to place a container on the vessel.

2.1.4 Mooring

Container ships are usually equipped with mooring winches, which are located on thefore and aft decks. The ship normally carries a limited number of steel lines on board ofthe order of 4. They are often used as spring lines to restrict the vessel in its longitudinalmotions. Further, container vessels normally carry a larger number of synthetic ropes,mostly nylon. Generally, 8 or 10 synthetic lines may be expected, depending on the shipsize (PIANC 1995).


Figure 5: Mooring arrangements

The ship is tied to the quay in a special mooring arrangement to prevent excessivemotion of the ship during loading and unloading. The function of the mooring system is toreduce ship motions. A moored ship can be compared with a damped-mass-springmodel. If the damping is correctly chosen the system remains in rest when a force isexerted on the system. The addition of damping changes the natural frequencies of thesystem. So by mooring a ship properly the natural frequencies are influenced and theship remains in rest position,

2.1.5 Ship motion

A free-floating vessel has six modes of freedom of motion: three translational and threerotational motions. In consequence, a ship exposed to waves may respond in sixdifferent modes or in any combination thereof. See Figure 5 for the definition of shipmotions.

X : SurgeY : SwayZ : Heaveφ : Rollθ : Pitchψ: Yaw

Figure 6: Ship motion

The analysis of ship motions was for a long period of time done in model tests. Later onnumerical models became sufficiently reliable to take over the role of physical models.The first models were linear. The assumption of linearity mentioned above holdsreasonably well for sailing ships in first order waves, i.e. the visible waves. In case of amoored ship it becomes less accurate because the reaction forces of mooring lines andfenders are generally not linear (Ligteringen 2000).

Ship motions are caused by several external actions. The geographical characteristics ofthe ships mooring-fender system play a major role in how the ship responds to externalactions. The following forces can cause ship motion:

- Wind


- Current- Waves, high and low frequency- Passing ships- (un)-loading operations.

2.1.6 Co-ordinate systems

Three right-handed orthogonal co-ordinate systems are used to define the ship motions:

Body-bound co-ordinate system G(xb,yb,zb).

This system is connected to the ship with its origin at the ship’s centre of gravity, G. Thedirections of the positive axis: xb in the longitudinal forward direction, yb in the lateral portside direction and zb upwards. If the ship is floating upright in still water, the (xb,yb)-planeis parallel to the still water surface.

Steadily translating co-ordinate system O(x,y,z).

This system is moving forward with a constant ship speed V. If the ship is stationary, thedirections of the O(x,y,z) axis are the same as those of the G(xb,yb,zb) axis. The (x,y)-plane lies in the still water surface with the origine O at, above or under the time-averaged position of the centre of gravity G. The ship is supposed to carry outoscillations around this steadily translating O(x,y,z) co-ordinate system.

Earth-bound co-ordinate system S(xo,yo,zo).

The (xo,yo)-plane lies in the still water surface, the positive xo-axis is in the direction of thewave propagation; it can be rotated at a horizontal angle µ relative to the translating axissystem O(x,y,z). The positive zo-axis is directed upwards.

Figure 7: Co-ordinate system

The time-varying motions are the motions of the ship in the steadily translating co-ordinate system O(x,y,z). In case of (un)-loading container ships the angles of rotation φ,θ and ψ must be limited to about 6 degrees, or 0.1 radian, but preferably less. For thesesmall angles it is allowed to assume that:


φφ =sin and φφ =cos

For small angles the transformation matrix from the body-bound co-ordinate system tothe steadily translating system is:

⋅

−−

−=

b

b

b

zyx

zyx

11

1

φθφψ

θψ

Using this matrix, the components of the time-varying harmonic motions of a certain pointP(xb,yb,zb) on the structure of the ship are given by:

φθφψθψ

⋅+⋅−=⋅−⋅+=⋅+⋅−=

bbp

bbp

bbp

yxzzzxyyzyxx

Equation 1: From rotation to translation

in which x, y, z, φ, θ and ψ are the motions of and about the centre of gravity, G, of thestructure. From the formula it is seen that the vertical displacement, zp, depends solelyon heave, pitch and roll motions. The offset in x-direction depends on surge, pitch andyaw motions, but in general the effect of surge and yaw is by far greater than the effect ofpitch. The same holds for the displacement in y-direction that is dependent on the sway,roll and yaw motions, in this case the combined effects of sway and yaw are mostimportant.

2.2 Problem definition

Due to an ever-increasing world trade ship sizes have increased. A larger ship has theadvantage that it has a larger transport capacity and so transport costs can be reducedsignificantly. But large ships are more expensive to build, operate and maintain. Tocompensate for the higher operational costs it is important to make maximum use of theship. A part of this optimisation process is to keep the turnaround times, the time spent inport for (un)-loading, of vessels within 24 hours.

The efficiency of the (un)-loading process is highly influenced by the movements of theship at berth. Motions at berth can result in (a) suspension of operation, (b) reducedcargo transfer efficiency (c) container damage (d) jamming of containers in cell guides; or(e) mooring line distress. In case of excessive motion at berth the decision can be madeto shut down the (un)-loading operation. This decision is based upon the safety reasonsconcerning man and machine.

When designing a new container terminal it is important to verify whether the design livesup to the expectations of the customer. The customer, usually a terminal operator,demands a harbour with a high handling rate to be able to guarantee a turn around timeof less than 24 hours to his clients, the shipping companies. In order to gain a high


throughput, or a short turnaround time, it is important to keep ship motions minimal. If thewave spectrum outside or inside a harbour is known a designer can calculate the shipmotions in response to the waves. This can be done with the aid of a ship mooringsimulation program. This program calculates the vessel displacement in time as well asthe mooring line forces and fender deflections. The outcome provides the engineer withvaluable information concerning the appropriateness of his harbour design. If the criteriafor (un)-loading containerships are combined with the calculated ship motions theengineer can estimate the downtime of the specific terminal. This downtime can be usedto evaluate the design. If the downtime is not satisfying the designer can try to optimisethe design by altering the fenders or the mooring layout. If this doesn’t have the desiredeffect he can alter the shape of the breakwater, the shape of the basin, the location ofthe berth within the basin or the berth orientation.

In the past decade a number of articles have been published about the limiting conditionsfor (un) loading ships. In 1995 PIANC Working Group 24 (PIANC 1995) published anoverview of the existing experience. PIANC suggested the following criteria for loadingand unloading container ships. The efficiency represents the hourly-handling rate, at 100% efficiency the crane operator puts through the maximum number of containers perhour. See Table 3 for containerships.

Surge (m) Sway (m) Heave (m) Yaw (°) Pitch (°) Roll (°)100 %efficiency

± 0.5 0.3 ± 0.3 N N ± 1

50 %efficiency

± 1.0 0.6 ± 0.6 ± 0.75 ± 0.5 ± 3

Notes: 1: ± indicates movement in both directions from rest position.2: Sway is away from the berth.

Table 3: PIANC criteria for container vessels2.3 Objective

Most of the presented criteria for dry bulk and oil carriers are considered reasonable andare based on many years of experience. But the criteria presented for container shipsare questioned by the industry and are likely to be outdated by the rapid growth of theseships.

The objective of the project is to review and if necessary improve the motion criteria forcontainer ships, based on computations and feedback from practice.

2.4 Starting points

- This study is restricted to ships at berth. No research will be done on sailing or berthingmovements

- Regarding the crane operation procedures only the procedure directly involving loadingand unloading operation will be subject of investigation.

- No research will be done beyond the point where the wind speeds exceed theoperational limits of the cranes and the process is terminated.


2.5 Assumptions

- Under influence of a travelling load a container crane can vibrate with amplitudes up to30 centimetres. These motions are only present during travelling of the load and areabsent once the container has reached the cell guides. For this study the crane is seenas a rigid structure that does not bend under the influence of loading and unloadingoperations.

- Containers are build according to ISO standards.


3 LITERATURE STUDY

3.1 Introduction

The following chapter will give a critical review of previously conducted research projects.First an individual description of the projects will be given. It is stated that the opinionswritten down in paragraph 3.2 represent the opinions of the authors only. In the last threeparagraphs, 3.3, 3.4 and 3.5, a comparison will be made between the research projectsdescribed in section 3.2. The comparisons will result in a new approach to the matter ofthe allowable ship motions for (un)-loading container ships.

3.2 Previous conducted research

3.2.1 P.R.C. Harris

In 1980 the New York based consulting engineers P.R.C. Harris (Bloom and Posch1980) did a study to define the container ship motion acceptance criteria. This was donefor the development of a new container terminal at the Port of Acajutla, El Salvador. Theships involved in the research project are first and second generation container ships, sorelatively small compared to modern vessels.

Acceptable levels of container ship movement were determined from the evaluation ofoperational experience and published data. Based on published data as well asdiscussions with port operations specialists, shippers and researchers, acceptable limitshave been established for normal container transfer operations on a cellular ship with aberth-mounted crane and a competent operator.

They mentioned the importance of a well-balanced mooring and fender system so thatthe natural frequency of the mooring system is beyond the range of the exciting wavefrequency. The damping of motions will result in more uniform movements, which willsimplify (un)-loading because the crane operator readily adjusts to ship motions if theyare of regular frequency and amplitude. With highly irregular movements the operatorhas less opportunity to make these adjustments. Also the stiffness of the mooring systemis of importance. With a stiffer mooring system the ship responds at a shorter naturalperiod and both movements and zero crossing periods are significantly reduced. There ishowever a corresponding increase in mooring line loads. The authors do not mention theamount of increase nor do they quantify the term stiffness.

According to P.R.C. Harris (Bloom and Posch 1980) the most important ship motions thathave effect on the (un)-loading of containers are surge and sway. Heave and yaw are notas significant as long as their movements are relatively slow. Roll and pitch areconsidered relatively unimportant for crane operations.

The experience of the crane operator is an important factor in achieving an efficientcontainer (un)-loading rate. A well-experienced crane driver will be able to operate inmore severe environmental conditions than a less experienced operator. Important arethe normal environmental conditions in which container operations are conducted. Wherethe crane operator is exposed to relatively large ship motions on a recurring basis hedevelops the necessary skills to operate efficiently under these conditions.


The acceptable motion limits or movements at which normal container transferoperations start to be adversely affected reflect a reduced handling efficiency of about10-15 %. The container ship motions were established by utilising information fromvarious researchers and it was mentioned that the various sources show a reasonablelevel of agreement on the motion limits. Furthermore limits were established at whichoperations would be so adversely affected as to cause shutdown. The criteria arepresented in the table beneath. The authors mentioned that the criteria could be largerfor non-cellular ships.

Type of motion Acceptable movement (m) Estimated shutdown levels (m)Surge ± 0.6 ± 0.8 to 1.5Sway ± 0.4 ± 0.5 to 1.0Heave ± 0.6 ± 0.8 to 1.3

Table 4: Harris criteria

Eight years later, in 1988, and on different continents, Japan and Nordic countries, twonew research projects were conducted. The Port and Harbour Research Institute inJapan did the first project. The Nordic countries initiated the second project.

3.2.2 Port and Harbour Research Institute (PHRI)

Although the outcome of the project has no relevance for this project since containerships were not a part of the investigation the project is mentioned because of its set-up,which shows a detailed and systematic approach to the matter. It is the only project thatproposes criteria based on wharf efficiency.

The Japanese research (Ueda and Shiraishi, 1988) investigates interruption andsuspension of cargo handling due to ship motions. The allowable ship motions wereestimated in terms of the type and size of a ship by executing numerical simulations. Thenumerical simulations were made for instances of interruption and suspension of cargohandling caused by ship motions. Also numerical simulations were made for normalundisturbed cargo handling operations. These values were evaluated and revisedrespecting opinions of cargo handling operators. Then the allowable ship motions forcargo handling at wharves were proposed.

The PHRI started their investigation with the calculation of the wharf efficiency. The wharfefficiency calculation is shown in the block chart beneath.


Figure 8: Wharf efficiency scheme.

For the calculation of the wharf operation efficiency the allowable ship motions for cargohandling are the most important items. Hence the focus of the report is solely on thedetermination of the allowable ship motions for cargo handling at wharves. For thecalculation the following method was used:

- Investigation of instances of interruption and suspension of cargo handling caused bywind and wave conditions. In three ports wave heights outside the harbour weremeasured. With the aid of diffraction models the wave heights in front of a berth wereestimated. With the aid of the diaries of port operators the moments of interruption andsuspension of cargo handling were obtained. These observations led to provisionalcriteria concerning the allowable ship motions for cargo handling.

- Numerical simulation, for all the instances mentioned above, ship motions werecalculated by means of the numerical simulation method.

- Statistical analysis, the result of the numerical simulation was statistically analysed andthe allowable ship motions for cargo handling were obtained.

- Inquiry to cargo handling operators on the provisional figures, since the provisionalfigures were estimated from the limited data obtained at a few ports, the provisionalfigures were evaluated by cargo handling operators at all the ports in Japan.

Numerical simulation of shipmotions for each wave periodand wave direction

Wave diffraction tests and/ orcomputations for each waveperiod and wave direction

Joint distribution of the waveheight and periods for eachwave direction

Observed wave data

Allowable ship motions forcargo handling

Allowable deep water wave heightfor cargo handling for each waveperiod and wave direction

Wharf operation efficiency

Ratio of the wave height infront of berths for each waveperiod and wave direction

Ratio of the non-exceeding of theallowable deep water wave height foreach wave period and wave direction

Allowable wave heights for cargohandling in front of a berth for eachwave period and wave direction


- Proposal of the revised allowable ship motions for cargo handling based on analyses ofthe data obtained from the enquiry.

3.2.3 Nordic Countries (Jensen et al 1990),

In the same year, 1988, the Nordic countries, Norway, Sweden, Denmark, the Faroeislands and Iceland, set up a new investigation. The purpose of their project was toestablish criteria for acceptable ship movements in harbours for safe working andmooring conditions. Their project is primarily concentrated on fishing vessels, ferries,coasters and container vessels with a Loa of 100-200 m

The project involved the following phases:- Literature study.- Pre-study to identify ports with ship movement problems that could be selected for

prototype measurements.- Prototype measurements and interviews with captains and port personnel.- Supplementary studies comprising interviews with port master and operators etc., and

comparison with results from existing hydraulic investigation of the same port.

First some remarks from the authors. They mention that the movements of rotations, i.e.pitch, roll and yaw, are almost independent on the mooring system. The only controlmechanism for this type of movement is proper berth orientation and location in thedesign phase of the berth. The periods of motions are dependent on the resonanceperiod of the ship, the wave spectrum, the berth angle relative to the waves, thereflection pattern for the waves and the type of berth. The translation movements of amoored vessel depend upon the type of ship, the mooring and fender system, the type ofberth, and the wave conditions. So, good fender and mooring design can significantlyreduce these motions. Typically, the natural period of the planar motions of a mooredship is for large vessels almost one order of magnitude larger than that of rotationalmovements, i.e. approximately 100 s to be compared with 10 s.

It is however important to notice that ship movements are only one of several parametersinfluencing the efficiency of loading and unloading. The acceptable movements of a shipin a certain port are dependent on:

- Local conditions.- (un)-loading methods.- Movement pattern of the vessel, e.g. the composition of movements.- Mooring and fender design.


For the acceptable ship movements the following two situations have been adopted:

i. Interrupted working situations

This situation is characterised by movements causing an interruption or a substantialreduction of the effectiveness off the (un)-loading operations. The corresponding criteriaare:

Containervessels

Surge (m) Sway (m) Heave (m) Yaw (deg) Pitch (deg) Roll (deg)

90-100%efficiency

0.6-1.0 0.6-0.8 0.6-0.9 0.5 1.5 3.0

50 %efficiency

2.0 2.0 1.2 1.5 2.5 6.0

Table 5: Nordic criteria

Note: 1: Occurrence of unacceptable surge, sway heave, roll, pitch and yawmovements for the 90-100% efficiency criterion should be less than 1week/year (2% of time)

2: The movements are maximum peak-to-peak values3: The container vessels mentioned have a Loa of 100-200 m, first generation

container ships.

ii. Safe stay at berth

The largest movements, for which no damage occurs to vessel or quay, provided that thevessel is well moored and the quay is well equipped with fenders, determine thiscondition. Furthermore it is important whether a vessel experiencing excessivemovement is able to leave the port and survive the storm either at sea or in an alternativeharbour. In some ports, the manoeuvring conditions in the harbour entrance are sodifficult that ships cannot enter or leave once the storm has reached the site. In such aport the aspect of safe mooring is even more important. The criteria presented for thesesituations are mainly intended for vessels smaller the 7000 DWT so they are notapplicable for container vessels.

Furthermore criteria are presented for the allowable wave height in front of the berth. It ismentioned that the wave height is only important if the waves are wind driven. In case ofharbour oscillations due to seiches or long wave phenomena the period of motionbecomes the governing parameter.

3.2.4 PIANC (PIANC 1995)

In response to the Nordic document (Jenssen et al 1990) PIANC (PIANC 1995) decidedupon review of the criteria for (un)-loading of all kind of ships. PIANC formed WorkingGroup 24 that published its conclusions in a practical guide as a supplement to bulletinno 88 in 1995. The practical guide contains an overview of the outcome for all thecategories of defined ship types. In addition to the guide there is an addendumpresenting details for each category of ship.


PIANC divided the world fleet into nine categories (small crafts and pleasure boats,fishing vessels, coasters and freighters, ferries and Ro-Ro vessels, general cargovessels, container vessels, bulk carriers, oil tankers and gas tankers) and assessed thefollowing aspects for each category:

- Description of the vessel, typical sizes, composition of the world fleet, future trends,etc.

- Description of typical berths and cargo handling equipment- Description of governing parameters for ship motions, cargo handling operations,

efficiency and safety.- Review and assessment of available literature, including recent model test results and

prototype measurements.- Recommendations for acceptable ship motions, mooring and fender line forces at

berths in safe working and safe mooring conditions, taking into account a reducedefficiency in cargo handling in case of worsening weather.

- Recommendations for improvement of operation and efficiency with respect to berthlocation and orientation, application of operational criteria for wind and waves,implementation of dedicated berths and modification of mooring arrangements.

First some overall citations on the handling of containers from PIANC Working group 24(PIANC 1995).

“To cross the oceans with maximum service speed large container vessels have aspecially designed shape wit a very short parallel mid-ship section to obtain a low blockcoefficient in the range of 0.6 to 0.65. Container vessels are very fast sailing vesselscompared to, for example, tankers and bulk carriers. Due to the design the number ofcontact points with the fender system along the berth is lower than for more bulky shipswhich make this ship type susceptible to yaw.”

“Main-port vessels sail to a tight schedule so they cannot tolerate any downtime.”

“Modern gantry cranes can handle up to 40-50 containers per hour but inevitable pausesreduce the absolute maximum handling rate. Normally in modern ports, newer gantrycranes handle about thirty to forty-five containers per hour. In most conventionalharbours it is often parameters other than ship movement, which determine the efficiencyof operations and thereby the handling rate.”

“The governing parameters for operation are vessel movements that are too rapid for thecontainer operator to follow. Spreaders cannot move quickly horizontally in all directions.The experience of the crane operator is of major importance since experienced driversare capable to operate safely in more severe conditions and with larger ship motionsthan a less experienced one. Roll, pitch and heave are governed mainly by thecharacteristics of the ship itself, whereas the moorings and the fender systems governsurge, sway and yaw to a large extent. For container vessels heave movements arerelatively slow and are not critical. Surge and sway are also rather easy to deal withespecially with modern cranes. In surge the container crane cannot follow the shipmovements. However the operator can postpone the operation and wait for the return ofthe vessel to a position where the operation can be undertaken. Sway is generally lessdifficult than surge, as only the trolley will have to follow the vessel. Yaw, especially


during loading, and roll are critical in quartering seas. Roll is definitely judged to be themost dangerous motion in beam seas and quickly reduces handling efficiency. Roll isparticular important where heavy loads have to be raised or lowered, and were duringsuch movements the crane has a chance of bumping against the hatch or cells as aresult of the vessel moves.”

“Motions at berth generally apply to periods of oscillation from 30 s to 120 s for surge,sway and yaw and to the wave periods for heave pitch and roll. Compared to other cargohandling systems, containers vessel operations are rather difficult ones.”

In Figure 9 some field measurements of moored ship movements are shown just toillustrate actual periods of vessel movement. These field measurements relate to a 2,000-tonne coaster moored inside Shoreham Harbour on the Southern coast of the UK during asouth-westerly storm. The mooring lines consisted of polypropylene ropes, generally taut,while the fenders consisted of rubber tires. Even though the vessel is not large it can beseen that the dominant periods of surge (the largest movement) is approximately 40 s,while sway and yaw occur at about 90 s. The dominant heave and pitch occurs at about 18s due to underlying swell at that period (identified in wave recordings made outside theharbour) while roll occurs at about 6 s, close to the natural roll period of the vessel.

In the above example, sway and yaw occur at relatively long periods for the size of vesseldue to the absence of breasting lines. The periods of horizontal movement are consistentwith the natural periods expected given the displacement of the vessel and the stiffness ofthe moorings. Here the vessel is moving like a heavy mass on elastic bands with themooring lines acting as the elastic bands. And the reason these resonant periods wereexcited inside the harbour was due to residual long waves at wave group periods (Section4.4), also identified in the field using a pressure sensor inside the harbour.

Clearly, the larger the vessel and the more compliant the moorings, the longer thesenatural periods will be. For example, large loaded bulk carriers (200,000 tonnes) onpolypropylene mooring lines can be expected to have resonant periods of several minutes,while loaded tankers of a similar size on wire moorings are likely to have resonant periodsof around a minute. If man-made fibre tails are used on wire moorings to limit mooringloads, then the resonant periods increase again due to the greater compliance of thecomposite mooring lines.


Figure 9: Field measurements of moored ship movements“Surge is influenced mainly by the mooring lines and is the type of movement thatgenerally causes mooring line failures. Sway and yaw can normally be controlled by thecombined effect of lines and fenders. Container ships generally have short mooring lines.For good control breast lines should be orientated perpendicular to the longitudinalcentreline of the vessel and as far aft and forward as possible. However gantry cranesmovements from one berth to the next along the quay, as well as transhipment, make itmore or less impossible to find good positions for breasting lines. Straddle-carrier, truck,train or other movements on the apron also make it impossible to obtain a good span forbreasting lines. Spring lines should control surge movement.”

“Relating the ship motions to a limiting significant wave height is not recommended. It isdifficult to give specific limits for the admissible wave height because this is closelyconnected with the wave period, the angle of incidence, the ship’s natural period ofoscillation, elastic properties of fenders and hawsers, etc.”


The criteria proposed by PIANC are listed in the Table 6.

Surge (m) Sway (m) Heave (m) Yaw (deg) Pitch (deg) Roll (deg)90-100 %efficiency

± 0.3-0.5 0.3 ± 0.3 N N ± 1

50 %efficiency

± 1 0.6 ± 0.6 ± 0.75 ± 0.5 ± 3

Table 6: PIANC criteria for containerships

Notes: 1: ± indicated movements in both directions from rest position2: Sway is away from the berth

“For containers below deck the angle between the guides and the vertical should neverexceed about ± 30. For a 40 ft container this gives a horizontal force of about 2 t. With a30 to 40 ft. hoisting distance to deck this corresponds to 0.6 m max movementhorizontally, which coincides with the 0.6 m limit on sway from Table 5.”

3.2.5 Hessenatie, d’Hondt

For the 12th international harbour congress in Antwerp mr E. d’Hondt (d’Hondt, 1999),from Hessenatie wrote an article on port and terminal construction. The focus of thearticle is on design rules and practical experience. On the issue of (un)-loading containerships he specially points out the importance of absolute minimum ship movement toachieve a high productivity. He then mentions the possibility of jamming of containers inthe cell guides due to rotations. Based on the tolerances of the cell guides and thedimensions of the cell guide and container he calculates the following criteria:

Pitching: 0.4o with respect to the horizontal planeRolling: 0.24o with respect to the horizontal planeCombined pitch and roll: 0.45o with respect to the horizontal planeHeave: Max amplitude 20 cm

Max speed 7.5 cm/s.

According to the author jamming starts to occur at twice the above mentioned values. Hefurther points out that his proposed criteria are totally out of line with the criteriapresented by PIANC in 1995.

The following paragraphs discuss the point of views from the various researchers.

3.3 Similarities

3.3.1 Influence mooring system

Both PIANC and Harris mention the importance of the stiffness of the mooring system.They both quote Slinn (SLinn 1979) who compared the response of a 44.000 t containership secured to a soft mooring system in a wave climate of long waves with a stiffermooring system. With the softer system the hourly container rates in adverse conditionswas reduced from the maximum still water rate of 30 to 19 cycles, a reduction of 36%.


For the stiffer system, the hourly container-handling rate in adverse conditions reducedfrom 30 to 26 cycles, a reduction of 13%. With the stiffer mooring system the shipresponds at a shorter natural period and both movements and zero crossing periods aresignificantly reduced. There is however a corresponding increase in mooring line loadswhich has not been specified.

The Nordic countries mention that the translations (surge, sway and heave) can becontrolled by a proper mooring design and that the rotations (roll, pitch and yaw) arealmost independent of the mooring system. PIANC on the contrary states that themooring lines can control horizontal movements (surge, sway and yaw) and that verticalmovement (roll, pitch and heave) are independent of the mooring design. PIANC is rightsince mooring line guidelines prescribe a maximum allowable angle with the horizontal ofabout 15 degrees. Thus mooring line forces are mainly horizontal and have a minimaleffect on vertical movements.

3.3.2 (un)-loading equipment

Every author acknowledges the importance of the (un)-loading equipment. The allowablecriteria differ for different kinds of loading equipment, for instance oil and LNG carriersare (un)-loaded via loading arms that allow more ship motion than (un)-loading viacranes or belts. Container cranes are judged to be the most sensitive for ship motions.

The average crane production is also subject of investigation. Newer cranes can handle40 to 50 containers per hour, according to their manufacturers. In reality however theiraverage production reaches only 20 to 30 moves per hour. If one wants to indicate theloss in productivity due to ship motion this figure is an important one since it determinesthe criteria. Use of the specifications provided by the manufacturer and the loss inproductivity will be dramatic, even with small vessel displacement. To obtain realisticproduction figures is quite difficult since container terminals are reluctant to share thatkind of information with the outside world. They fear that these figures might be usedagainst them by the competition to attract new customers.

3.3.3 Crane operator

The most striking resemblance is that all the researchers first determined criteria andthen presented these for verification to terminal operators and crane drivers. This wasdone in order to establish a link between theory and practice. A large-scale questionnairewas entailed by the Port and Harbour Research Institute who sent out questionnaires tohundreds of port operators. The response was disappointing since about 20 % returned.Furthermore they found a large variation in the results. They concluded that operatorsthat have never experienced troubles of cargo handling due to ship motions estimate theallowable ship movements far greater than operators that frequently deal with shipmotions. Thus it was questioned whether to take the mean of the data as the critical shipmotion for cargo handling.

The Nordic countries used a questionnaire in parallel with the measurements in order toquantify the results of the measurements. In their questionnaire the focus is on theopinions of the ship personnel about whether it was necessary to interrupt the operationsand about critical mooring situations. The results are not published.


PIANC and Harris remain vague about their consultations with port operators, there is nooverview of the questions asked nor was their result published.

3.3.4 Literature study

To obtain criteria for the motion of moored ships all the researchers did a literature study.PIANC, the Port and Harbour Research Institute, and the Nordic country’s did it just topresent an overview of the knowledge available. After the literature study they followedtheir own strategy to determine the criteria for (un)-loading ships. P.R.C. Harris on theother hand used the outcome of their literature study as the basis for the criteria. Theyused six research projects that were conducted prior to 1980. From these projects theaverage of the ship motion criteria was calculated and used as a base point for theirconversations with port managers. The six research projects used by Harris wereconducted prior to December 1980 and are untraceable.

3.4 Differences

3.4.1 Acceptable downtime

The Nordic countries conclude in their report that frequency of exceedance of theallowable ship movements for 90-100% cargo handling rates in ports should be less than1 week per year, or 2 % of the time. PIANC on the contrary mention that main-portcontainer vessels sail on a tight schedule so they cannot tolerate any downtime.

These different views can easily be explained. The Nordic countries focused theirresearch on relatively small harbours, so called spoke harbour. Spoke harbours have alocal function and downtime is more easily accepted by its users. PIANC on the contraryfocused on large container harbours, alias hub harbours. Hub harbours have a globalfunction and are visited by large containerships that sail to a tight schedule, so downtimeis unacceptable. This explains the difference in allowable downtime.

3.4.2 Criteria

Although the Port and Harbour Research Institute did not do any research on containerships they provided criteria for general cargo, oil and bulk carriers. These criteria aresignificantly smaller than the corresponding criteria from PIANC Working Group 24.

PIANC (PIANC 1995) reports that heave motion is relatively slow thus not critical. Heavehowever can be caused by swell, swell amongst others can be the cause for rather largesurge motions. Vertical ship displacement is hard to judge from above, certainly from thecrane driver position. This means that in case of heave the driver cannot lower thecontainer close to the deck of the ship to prevent a collision. Assuming that in case ofsurge the crane driver waits for the return of the vessel before attempting to lower thecontainer than in case of heave accompanied by surge the driver has to decide to lowerthe container from a greater height than usual. Since a greater height means a longerlowering time the chance of successful placement decreases with increasing heavemotion.


3.4.3 Relation rotation-translation

The Port and Harbour Research Institute geared the criteria for yaw and pitch to thecriteria for heave and sway. The effect of yaw and pitch in terms of vertical or horizontaldisplacements at bow and stern are proportional to the ship length. So if one proposed ayaw criterion of 1 degree for a 200-m long ship this results in a sway of 0.9-m at the bowor stern. If at the same time one proposed a criteria of 0.6-m for sway the two criteriaconflict. The PHRI foresaw this and geared up the criteria for rotations and translationscontrary to the other reports.

3.4.4 Cell Guides

While Harris concluded in the 1980’s that roll and pitch are relative unimportant for craneoperators, PIANC concluded that roll has a major effect on the (un)-loading process ofcontainers stored below deck in cell guides and that roll quickly reduces the handlingefficiency. Also d’Hondt (d’Hondt 1999) mentioned in his paper the effects of rotations onthe (un)-loading process.

On one side there are the criteria published by PIANC. These are based on informationof port operators although it is unclear how PIANC selected the ports that providedinformation. And as has been stated before, only port operators which frequently copewith ship movements are able to give an objective set of criteria. For the roll and pitchcriteria PIANC calculated that a roll angle of 3 degrees results in a horizontal force of 2tons on the cell guides. They mentioned that jamming starts to occur at twice the above-mentioned values. The importance of the 2-ton horizontal force is unclear as well as whyjamming start to occur at twice the mentioned value.

On the other side there are the criteria published by d’Hondt. He calculated criteria onthe basis of the tolerances in the cell guides. He assumed the cell guides and thecontainer to be infinitely rigid. This means no deformation of the structure and that theforce exerted by the container on the cell guides increases linearly with the rotation of thecell guide. This leads to quite conservative criteria for the allowable roll and pitch modes.According to D’Hondt the containers touch the cell guides at 0.5-degree and jammingstarts to occur at 1-degree roll angle.

Consultation with DUT Faculty OCP (Gerstel, 1999) about this subject leads to believethat the matter is far more complicated than PIANC and d’Hondt describe. The system ofcell guides is more complicated and cannot be represented by an infinitely rigid model asPIANC and d’Hondt did. In reality the cell guides have certain stiffness and moment ofinertia, which may vary in all three directions, x, y and z. The stiffness determines theability to deform and is dependent on the internal structure of the cell guides. Themoment of inertia is dependent on the type and shape of steel used for the cell guidebeams. Of further importance is the response of the structure when a collision occurs.The response can be very soft, like a squash ball that quickly losses its energy onimpact, or very hard, like billiard ball that does not absorb the energy but passes it on toanother ball, or somewhere in between. The response of the cell guides is alsodependent on the occupation rate of the adjacent cells. If the adjacent cell guides are allloaded with containers than the ability of the cell guides to deform freely is blocked thusthe response is different. And again the loading rate of individual containers is important.


Important is also the vertical location of the container in the cell guides. The deeper youget inside the hold the stiffer the system probably is.

The question is further whether there exists something like a uniform definable cell guidestructure. If every shipping line designs its own type of cell guides then it will be evenharder to determine uniform applicable criteria.

As one can see the total system of cell guides is quite complicated so simple rules ofthumb may lead to very conservative values for the allowable rotation angles, such asthe criteria published by d’Hondt. The best way to establish criteria for roll and pitch is bysimulation the behaviour of the cell guide structure under the normal (un)-loadingprocess. For this simulation it is necessary that the model to be built is an exact copy ofthe cell guide in order to get realistic values. The program could simulate numeroussituations leading to well founded criteria.

3.4.5 Field measurements

The Port and Harbour Research Institute (Ueda and Shiraishi 1988) from Japan and theNordic country’s (Jenssen et al 1990) took quite a different approach.

The Nordic countries measured ship movements, mooring line forces, wind, wavesoutside the port and inside the port and in one occasion fender deflections. A total of 117measurements were carried out on different type of ships. Results from the fieldmeasurements have been related to the length of the ship and it was determinedwhether it was possible to unload or whether the movements were to excessive foroperations, but still allowed the ship to stay at berth.

The PHRI measured the wave height outside the harbour and used a diffraction model tocalculate the wave height in front of a berth. Via the diary of the terminal operator theydetermined when loading and unloading operations where interrupted, ceased and whenships had to abandon berth. Afterwards they linked the wave height in front of the berthto the motion criteria. The PHRI presented the criteria as the harbour calmness index;this means based on an allowable wave height in front of the berth.

Field measurements are a good way to approach the matter since they represent the realworld. Problem is that one needs an uninterrupted (un)-loading process. If the (un)-loading process is hampered due to other factors than ship motion alone themeasurements become unreliable. Especially for containers there are a lot of otherfactors that can disturb the continuity of the process. Think about the delivery process ofcontainers from and to the quay, the change of bay, break down of the crane, removaland placing of twist locks, checking of seals, etc. Furthermore ports do only encountersignificant ship motions during a few days a year, so good field measurements require along lasting campaign.

PIANC is the first to mention in their report that the vertical velocity of the motion isimportant. If you look through the eyes of the crane drivers this is completely logic sincethe driver is positioned some 30-meter above the ship’s deck and can hardly see theexact landing spot. From his position it is quite difficult to estimate the vertical height ofthe container relative to the ship.


3.5 Shortcomings

3.5.1 Period of motion

Some reports mention the importance of the motion’s velocity while none of them presentcriteria for the period of motion. The velocity determines the amount of time a cranedriver has to make the decision to lower a container. The ability to react correctly reduceswith increasing velocity. So the period of motion in relation to the amplitude might be anindication of the success of placement.

3.5.2 Relation throughput- ship motion

Express the loss in productivity in time in order to make it quantifiable. In this way theextra time a driver needs to position a container on a moving landing spot can be addedto the normal cycle time. On the base of the average total cycle time one can calculatethe hourly throughput. In this way it is also possible to gain insight in the decrease of the(un)-loading process with increasing ship motion.

Further more it could be interesting to develop a coefficient that can be used to calculatethe hourly throughput in relation to ship movement. This would facilitate the calculationsof the yearly throughput in a certain harbour or to calculate the loss in productivity due toship motion in that harbour. Same holds for downtime calculations.

3.5.3 The human factor

Every report and paper mentions the importance of the experience of the crane driver butnone of them seriously investigated the matter. The experience of the driver determineswhether he is capable to position a container on a moving landing spot and the timeinvolved. In the past a relation between horizontal displacement of a moored ship andproductivity of the (un)-loading process was made.

In 1979 P.J.B. Slinn (Slinn 1979) simulated loading techniques to study the effect of twotypes of ship movement on container handling rates. A device was developed that, whenused with a container crane, simulated as closely as was practicable the loadingtechniques used in practice. A theoretical model was established to calculate the extratime needed to position a container on a moving ship.

During this simulation the crane driver hoisted the container to 10 meters above the testcell and quickly lowered it to about 20 cm above the moving cell. Then the crane driverwaited until the cell passes under the container before attempting to place it. This wasdiscovered by Slinn and confirmed by harbour authorities that cope with occasional shipmovements due to wave action. The reason that the driver does not follow the movingcell guides is the randomness in direction of ship movement and the swinging of thespreader/ container.

The mean number of oscillations of the cell can be expected to be a significantparameter because it is a measure of the number of opportunities the waiting driver hasbefore locating the container in the guides. So during one oscillation the driver has two


opportunities. It was found that the reaction time of the driver and the machinery was ofthe order of 1 second. Further more it took about 2 seconds to lower the container fromthe 20-cm above the cell. Slinn figured out that the following relation exists between themean number of trials to succeed and the resultant cell velocity V:

Vmk ⋅= with

222

222

22

⋅

+

⋅

=yx T

YT

XV ππ

and

xtm

∆∆=

With: k = Mean number of trials to reach successV = Resultant cell guide velocity [m/s]∆t = Time needed to lower container. [s]∆x = Initial distance between container and cell guide. [m]X = Amplitude surge. [m]Tx = Period surge movement. [s]Y = Amplitude sway. [m]Ty = Period sway movement. [s]

From this it follows that the extra time needed to position a container on a moving ship is:

zTk ⋅⋅21

With:Tz = Max. period of Tx or Ty.

So the total cycle time is lengthened leading to a lower hourly throughput.

The human factor is a decisive factor in the process. A skilled driver is capable ofreducing the swinging of the spreader while travelling from the quay to the ship. Evenunder high wind loads an experienced driver is capable of keeping full control over hisspreader. This means that the efficiency of the process is heavily dependent on theexperience of the driver.

A higher degree of control over the spreader also means that experienced drivers arecapable to achieve higher (un)-loading rates even with larger ship displacements. Thusthe allowable criteria for (un)-loading container ships should be dependent on the cranedriver. Introducing a reduction factor for the relation between driver and his theoreticalachievable hourly throughput under normal conditions could do this.

Most important is the hand-eye co-ordination of the driver. This factor determines thelearning speed of a new driver and maximum achievable skill level. Hand-eye co-ordination again is dependent on a number of physical and mental conditions. Forinstance people with dyslexia are known to have a lesser hand-eye co-ordination. Alsothe shift duration and the outfit, the vibrations and accelerations of the cabin have an


effect on the performance of the driver. To investigate this matter a model has beendeveloped. A description of the model is given in chapter 4

3.5.4 Rotation criteria

The vertical transport of a container in the cell guide can be hampered by an increase infriction due to the rotation of the cell guides. These rotations may even lead to thejamming of a container in the cell guides. The exact effect of the rotations on theefficiency of the (un)-loading process is unclear.

The best possible way to investigate the relation between rotation and efficiency wouldbe by setting up a numerical model to simulate the transport of a container in the cellguides. From this simulation model one could determine the effects of a rotation on thetime that is needed to lower a container into a confined space that is rotated. This timecan then be compared with the time it would take to lower a container into a non-rotatedcell guide. The difference between these two times can then be used to calculate thereduction of the efficiency of the (un)-loading process. This is outside the scope of thisstudy.

Another way to derive the criteria for the allowable rotations is by means of aquestionnaire. In the questionnaire operators are can be asked about their personalopinions about the criteria for (un)-loading containerships.

3.5.5 Should criteria be uniformly interpreted?

It can be considered common sense that the highest container handling rates will beachieved if ship displacement is absent. But due to environmental conditions this isalmost never the case. Although some harbours in the world provide a natural shelterwhere ships at berth show minimal displacement, i.e. Antwerp and Rotterdam, mostdon’t. Harbours without these geographical advantages require expensive breakwatersto provide a good shelter for (un)-loading vessels. And although breakwaters areexcellent to keep out the high frequency waves, i.e. wind generated waves, for lowfrequency waves they are quite ineffective. If the criteria would be interpreted very strictlyfor these kinds of harbours this could lead to a very expensive design since largebreakwater would be needed to provide a smooth wave climate inside the harbour. Soshould criteria be uniformly interpreted?

A small harbour in the third world will probably have a throughput that is just big enoughto justify a container terminal on their premises. But due to the low throughput, comparedto Rotterdam that has a hub function, downtime will be accepted more easily. Or in otherwords the allowable ship motion can be greater in a spoke-harbour than in a hub. But ifone would apply the criteria strictly for (un)-loading container ships in both harbours itwould probably lead to either to much loss in productivity in the hub or to a veryexpensive spoke.

Thus criteria should not be interpreted in a straight way. The allowable ship motionshould be determined upon the harbour throughput and an economic evaluation of theharbour design should be made. In this economic evaluation it is necessary to determinethe equilibrium between the cost of wave protection structures and the added value for


the harbour expressed in dollars per ton cargo handled. In this light it is more importantto find a relation between the handling rate and ship motion.

3.6 Conclusions

From the literature study the following conclusions can are drawn:

− The mooring has a significant influence on the motions of a moored vessel andconsequently on the efficiency of (un)-loading operations

− The efficiency of the (un)-loading process is heavily dependent on theexperience of the crane driver

− The efficiency of the (un)-loading operation of a container ships is sensitive toship motions

3.7 Recommendations

The following recommendations are given:

− Research into the relation of the period of ship motion with respect to thehandling rates.

− Research to establish a relation between ship motions and handling rates.− Consultations with harbour masters that have experience with hampered (un)-

loading operations due to ship motions.− Research into the possible jamming of containers in the cell guides due to roll

and/or pitch.− The conduction of field measurements to directly link ship motions to handling

rates.

Following the conclusions and recommendation the idea is to develop a model to furtherinvestigate the matter of “criteria for (un)-loading containerships. The model will bediscussed in chapter four.

Furthermore an inquiry will be held amongst harbour masters to gather information fromthe real world. The questionnaire will be discussed in chapter 5.


4 MODELLING

After careful consideration of all findings presented in the literature study the choice hasbeen made to develop a computer simulation model to simulate the loading procedure ofa containership. The objective is to determine the extra time needed for placing acontainer onto a vessel subjected to external forces. Consequently a relation might bederived between the motions of the vessel and the (extra) time it takes to place acontainer in the cell guides. The model is initially designed for simulating the loadingprocess but can probably be also used for unloading simulations.

4.1 The model

The model is based on the loading cycle as described by Slinn, 1979. First a crane driverpicks up the container at the quay and then transports it to the prescribed bay on the shipand quickly lowers it to about 20-cm above the cell guide entry. At this point the driverwaits for an appropriate moment to lower the container the last 20-cm into the cellguides. His experience, combined with the visual information of the location of thecontainer relative to the cell guide, make him to decide to lower the container or to wait abit longer until a better moment occurs. If he lowers the container and it enters the cellguide than a placing is successful, if he misses the cell guide then the container is raisedagain and the driver prepares for a new attempt. It is important to realise that betweenthe moment the driver decides to lower and the actual arrival of the container there is atime lag of three-seconds. These three seconds are the sum of a one-second reactiontime, and a lowering time of two-seconds. During these three seconds the cell guidesalso move. These two seconds are an average but are dependent on the type of craneused. So through the eyes of a crane driver the situation might be perfect at the time hedecides to lower but due to the three seconds time lag the final situation is not necessaryas perfect as anticipated.

In the model use will be made of a training module that will allow to build up theexperience of the crane driver. The results from the training module (experience) willthen be used in an operational module. The operational module will represent the actualloading phase. This phase starts at the quay where a container is picked up andtransported to the ship. The phase ends with the positioning of the container on the shipand the return of the spreader to the quay. Note that the oscillating motions of thecontainer itself are not included in the model.

The result is a model that predicts the hourly container handling rates as a function of themotions of a moored container vessel. The motions of the vessel will be irregular.

4.1.1 Training module

In real life crane operators are trained before they are put into service on a containercrane. Training in Rotterdam is done at the Shipping and Transport College where theyuse a crane simulator to train new operators. The training of a human crane operator isessentially a trial and error method. Through the training on a simulator, the operator istrained to interpret the visual information he receives and to select the right moment tolower the container into the cell guides. The selection of the right moment initially is a trialand error decision, but after the necessary misses and hits, the experience (method of


selecting the right moment) of the crane operator improves. It is mentioned thatessentially the only information a human crane operator has when placing the containerin the cell guides, is the position and direction of movement of the container relative tothe cell guide. However he does not know the exact distance and velocity (in measuredunits). A computer model generally works with measured units, so in order to eliminatethe absoluteness of the model one needs to eliminate this in the training module.

Set up of the training module

In the training module the centre of the container in the spreader is treated as a fixedpoint in time. The cell guide describes a regular sinusoidal motion in time and thedistance between the container and the cell guide is known at any time. See figure 8beneath for an impression.

Figure 10: Model definition

At t=0 the container and cell guide are precisely located above each other when the cellguide starts to move. After a random interval T1 the first container arrives in the system.The model randomly decides to lower the container into the cell guides. But between thetime the decision is made and the actual time of arrival of the container in the cell guidesthere is a time lag of three seconds. During these three seconds the position of the shiphas also changed. If at this instant the container fits within the cell guides, the placing isa random success. At this moment the information which has resulted into this success isstored. This information is the position of the container at the time of the decision tolower. The graph below shows an example of the stored information.

For the listing of the full training module reference is made to appendix 2

∆X Vx(t)

Y

X

Cell GuideContainer

Vy(t)

∆Y


Figure 11: Example training results

Every point in the graph represents a position at which one decided to lower a containerunder the prevailing motion that led to success. By repeating this for a large number oftrials, the computer builds a database containing conditions (information about X, Y)under which there will be a success.

4.1.2 Operations module

In the operational module the operations performed by a crane operator are translatedinto a computer model. The model starts at the quay where a container is picked up andtransported to the desired location on the ship. Once arrived above the cell guide themodel waits for an appropriate moment to lower the container. The decision to lower isbased on the actual position of the container relative to the ship in relation to the pointsobtained from the training module. However the decision to lower the container can stillresult in a miss (see below). If the placement is successful the model returns to the quayfor a new container. If the container misses the cell guide than it will be hoisted againand the driver waits for a new moment. The cycle ends after a successful placement hasoccurred. In this way one can calculate the number of containers that can be loaded perhour under the governing conditions.

The operational module contains a few specific items that will be explained in thefollowing section.

1. Decision process

The decision module is a vital part of the model. It enables the program to make anobjective decision to lower a container into the cell or to wait. The decision made isbased on the experience of the crane driver, which is represented by the training module.

The graph from the training module simply represents combinations of x and y that leadto successful placement of a container. Remember that x and y are relative to the centreof the cell guides. If one would project the actual offset of the container in time on thisgraph it can be used for deciding a proper moment to lower the container. This is rathersimple for a human operator, but not for a computer.

Training results

-0,2

-0,1

0

0,1

0,2

-0,15 -0,1 -0,05 0 0,05 0,1 0,15

Offset in x-direction (m)

Offs

et in

y-d

irect

ion

(m)


In order to let the model decide whether to lower a container or to wait the actual offsetoff the cell guides is projected on the graph from the trainings module, see Figure 11.With this projection the graph can be divided into four rectangles that function ascounters. The counters are continuous in time and calculate how many points from thetraining’s module are on the top left side, counter one, on the top right side, counter two,bottom left, counter three, and bottom right, counter four, of the actual position, seeFigure 12. This leads to four counters that vary in time and in value. The value of acounter is the sum of all point in the square, divided by the total number of points fromthe training module The value of the counters varies between one and zero. If a counterhas the value of one this means that all training points are on one side of the actualposition. This indicates that the container is not in a position to be lowered into the cellguides. Zero on the contrary means that one side of the actual position there are nopoint. If the actual position is with the point range the value will be between zero andone.

So there are four counters that are related to the movements of the cell guides and thatprovide information about the position of the cell guides in relation to the container. Theirvalue indicates whether one should take action or not. In an ideal situation one shoulddecide to lower a container if all counters are between 0.99 and 0.01. This wouldrepresent the outer limits of the decision module. In reality one will never decide on thelast or first possible moment. A human will always try to build in some safety margins, ortranslated into the decision module he will narrow down the square.

Figure 12: Definition of decision square

In the following parts this will be called the decision square.

2. Uncertainty factor

1 2

43

Cell Guides Adjustable boundaries of decision rectangle

Centre of container


The uncerteinty is a function of the vessel motion. The larger the motion the larger thedifficulty for the crane operator to reliably asses the position of the container relative tothe cell guide. The difficulty has been assumed to be a normal distribution with averagezero and a standard deviation depending on the vessel motion. At the moment ofdeciding to lower the container a random (X and Y) distortion factor is drawn and addedto the relative (X,Y) position of the container.

3. Vessel motions

The best way to simulate vessel motions would be by generating realisations ofmeasured spectra of vessel motions for container vessels. Unfortunately these spectracould not be found and the suggestion was made to use a wave spectrum. This is quitelogical since free floating vessel show a linear response in relation to a wave spectrum.This linearity only holds for free floating vessels. For moored vessels the presence ofmooring lines introduces non-linear effects and the wave spectrum cannot be lineartransformed into a ship motion spectrum.

The shape of various wave spectra were compared to an available spectra of a of amoored LNG vessel. The strongest relation was found in the Pierson-Moskowitzspectrum. More information about the spectrum can be found in Pierson and Moskowitz(1964).

The amplitude and period of the regular ship motion are used in the training module andserve as input values for the spectrum. To generate the spectrum the average motionsare recalculated to significant motions. From this spectrum the irregular ship motions areobtained.

Although the spectrum does not exactly describe vessel motions it is a first step in theprocess to obtain ship motions. In a later stage it is possible that a more advancedspectrum that better describes moored container vessel motions replaces the used PM-spectrum.

4. Throughput rate

The throughput rate as used in the model has been set at 30 containers per hour, so thecycle time of undisturbed (un)-loading is 120 seconds. This figure is subject of manydiscussions. Port operators will argue that the throughput is much higher simply becausethey refer to maximum achievable throughput under perfect conditions. But if one takesinto consideration that cranes have to switch bays, crews have to change shifts, hatcheshave to be placed or removed, etc, and then the average throughput will be much lower.So the throughput rate should be based on the operational cycle time which is about 120seconds or thirty containers per hour.

Furthermore it will be possible to transform the output of the model so that the calculatedthroughput is not measured in containers but in a percentage of the average throughput.This would make the outcome independent of the average throughput rate.


Framework

The framework gives a brief overview of the steps made by the model.

Training Module Operations Module

Figure 13: Model framework

The full listing of the model can be found in Appendix 2

Start, T=t0, X(t0)=0

Pick random Tw, Tw = ∈ [0,T]

Lower container

End

X(T2) < tolerance ?

t1= tw, X(t1)

Write value to file (X2, Y2)

Placing successful

T2=T1 +tz+tr, X(T2)

Start, T=t0, X(t0)=0

Ta, calculate X(ta)

X(t2) + disturbance

Decide to lower container

End

X(t2) < tolerance ?

Compare X(ta)≅Xsuccess

Write value to file, Tw, A, Tp

Placing successful

T2=Ta+ tz+tr, X(t2)

Ta = T + t

T = t + ∆t

No ?

No ?

T = t + tz + tr + ∆t

No ? Yes ?

Yes ?

Yes ?

T = t + tcycle


4.2 Calibration

For calibration the results from tests done by Slinn, (Slinn 1979), were used. In his testsSlinn simulated (un)-loading operations on the quay by using a steel frame that could bemoved in two horizontal directions. The steel frame obviously represents the cell guidesand the movements represent the vessel displacements. Slinn measured the number ofattempts needed by a crane driver to successfully place a container on a moving landingspot. Figure 11 displays the measurements. The resultant velocity is set on the x-axiswhile the number of trials needed is on the Y-axes. Furthermore the graph shows aregression line of means. For each velocity Slinn also denoted the maximum andminimum number of attempts needed.

Figure 14: Graph Slinn

From figure 11 it can be directly noted that the regression line coincides with the origin.This is considered odd since every driver will need at least one attempt before asuccessful placement can occur. Therefore the graph has been re-drawn going throughX=0, Y=1.


Figure 15: Calibration graph Slinn

The resultant velocity on the x-axis is calculated with the following formula:

222

222

22

⋅

+

⋅

=yx T

YT

XV ππ

With:V = Resultant velocity [m/s]X = Amplitude surge. [m]Tx = Period surge movement. [s]Y = Amplitude sway. [m]Ty = Period sway movement. [s]

As can be seen the resultant velocity is dependent on the period and amplitude ofmotion, as well as in X and in Y direction.

From the graph four points are taken for calibration purposes and with the aid of theformula the corresponding amplitude and period of motions have been calculated. Theperiod of motion has been set at 40 seconds and remained constant. So only the valueof the amplitude differs from point to point. Table 7 shows these points and theircorresponding values.

Testnumber:

Resultantvelocity.

Amplitudeof motion.

Period ofoscilation

Mean numberof attempts

1 0.1 m/s 0.65 m 40 s 1.82 0.2 m/s 1.25 m 40 s 2.63 0.3 m/s 1.88 m 40 s 3.44 0.4 m/s 2.55 m 40 s 4.2

Table 7: Calibration Points

Calibration graph Slinn

0

1

2

3

4

5

6

7

8

9

0 0,2 0,4 0,6 0,8Resultant velocity

Mea

n of

atte

mpt

s

Slinn


Furthermore Slinn used regular sine shaped motions for the cell guide motion and helimited the time the driver had to a maximum of two minutes, or 120 seconds to lowerone container. The maximum shift duration for a crane driver was further limited to twohours. Al these limitations have been built in to the model in order to make the matchbetween the developed model and the test carried out by Slinn as accurate as possible.

With the model adjusted to the governing conditions of Slinn the calibration took place.The points of the table where entered in the model and runs were made. In each of theseruns the outcome, or the number of attempts needed, was compared with the resultproduced by Slinn. Adjustments to the model could be done by resizing the decisionsquare or by increasing/ decreasing the distortion factor.

While calibrating it was found that variations in the area of the decision square had littleinfluence on the outcome. The uncertainty factor however has a significant influence. InTable 8 the results of tests done with different uncertainty factors are presented. Fromthe table is can be concluded that the best fit is obtained with the amplitude of motiondivided by ten.

Resultant velocity A/9 A/10 A/11 Slin0.1 1.92 1.78 Too low 1.800.2 Too high 2.75 2.53 2.600.3 Too high 3.44 3.3 3.390.4 4.23 3.97 Too low 4.19

Table 8: Calibration uncertainty factor

4.3 Runs

After successful calibration, production runs were made to obtain the reduced throughputrates due to ship motion. Given the time consumed to run the model only a limitednumber of runs have been made. These runs are made to give an impression of theoutput of the model.

The production runs have been made with two types of bay motions (surge and/ or sway)The imposed motions have a period of motion that remained constant while theamplitude taken increased each other run. For surge the period of motion has been setat 120 seconds while for sway a much shorter period of 18 second has been chosen.These periods correspond to the natural periods of motions for large vessels.

The increase in amplitude has been done in small steps of 0.1 m until 2 metres, from 2 to3 meters the increase was done in 0.2 m steps and above 3 meter the step size hasincreased with 1 meter at the time. The further increase stopped when the processefficiency dropped below 4 containers per hour, this represents an 86 percent drop in theefficiency.

The outcome of each run is the number of containers that can be loaded per hour underthe governing conditions.


Apart from runs made with a constant period and changing amplitudes, runs were madewith fixed amplitude and increasing periods.

4.3.1 Results

In Table 9 the first results of the model are shown. In this case the period of surge is 120seconds and for sway 18 seconds. The number in the table represents the number ofcontainers that can be handled under the corresponding conditions. For example, if avessel is subjected to 0.5-meter sway motion in combination with 0.3 meters surge thehandling rate will be around 16 containers per hour per crane.

Sway motions in meters 0,0 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 0,0 29 29 27 23 22 21 20 16 19 16 14 14 13 0,1 29 29 27 22 22 20 18 18 17 13 15 14 14 0,2 29 28 23 20 19 18 16 16 16 11 9 11 9 0,3 27 25 21 18 17 16 13 14 11 12 11 8 9 0,4 26 24 21 16 15 12 11 12 11 9 8 6 7

0,5 24 23 16 12 13 12 10 9 9 8 8 6 80,6 23 22 17 13 13 10 8 8 7 8 6 4 60,7 22 21 16 12 10 9 7 6 7 7 7 6 60,8 20 19 15 10 9 7 7 7 6 6 7 5 40,9 18 18 13 9 9 8 6 6 5 7 5 3 31,0 18 17 11 7 6 5 7 5 5 6 5 4 31,1 17 18 12 8 7 5 5 5 6 5 4 3 1,2 16 15 11 10 8 7 5 5 4 4 3 1,3 17 15 12 8 7 7 4 4 3 3 Su

rge

mot

ions

in m

eter

s

1,4 14 12 10 9 7 5 3 5 2 1,5 14 15 10 8 5 4 3 2 1,6 14 11 9 8 6 1,7 14 12 8 8 5 1,8 13 12 9 8 5 1,9 12 12 8 8 6 2,0 12 12 7 5 6 2,2 11 12 8 6 4 2,4 9 10 7 4 3 2,6 10 7 6 4 2,8 11 8 5 6 3,0 9 8 4 2 4,0 5 5 4 6,0 5 5 3 8,0 4 4 10,0 2

Table 9: Reduced handling rates

From these runs it can also be clearly seen that handling rates gradually drop if themotion of a moored vessel only consists in one particular direction. For the same


situation with pure surge, handling rates do not reduce significantly and in case of puresway a reduction of about thirty percent would have occurred. But if the motion exists intwo directions, a combination of surge and sway, handling rates reduce quickly to afraction of the normal handling rates. In the example above one can see that with onlyhalf a meter sway and 0.3-meter surge the handling rate reduces by nearly fifty percent.

To investigate the influence of the period of motion on the container handling ratesanother run has been made in which the amplitude remained constant while the periodwas increased. In Table 10 the result of the runs are shown. By plotting these results intoFigure 16 it can be clearly seen that the period has a significant influence on the handlingrates. From Figure 16 it can be read that with amplitude of 0.5 meter and a period of 180seconds one can handle approximately 26 containers per hour. If under the sameconditions the period is reduced to 20 second one can only handle about 21 containersper hour.

Amplitude Period of motion (surge)(m) Tx=20 s Tx=90 s Tx=120 s Tx=180s0,01 30 30 30 300,10 28 29 29 290,20 26 27 29 290,30 24 26 27 280,40 23 24 26 270,50 21 22 24 260,60 19 21 23 240,70 18 19 22 240,80 17 19 20 220,90 15 18 18 211,00 15 17 18 211,10 14 17 17 191,20 13 14 16 191,30 12 14 15 181,40 14 14 171,50 13 14 171,60 13 14 151,70 13 14 151,80 12 13 141,90 12 12 142,00 12 12 142,20 11 11 132,40 10 10 122,60 9 10 122,80 9 9 113,00 8 8 114,00 6 7 86,00 5 5 58,00 4 4

10,00 4

Table 10: Reduced handling rates for pure surge


Relation Amplitude-Handling rates

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 4,50 5,00 5,50 6,00 6,50 7,00 7,50 8,00 8,50 9,00 9,50 10,00

Amplitude

Han

dlin

g ra

te p

er h

our

T= 120 s

T=90 s

T= 20 s

PIANC 50 %

90-100 % grens

50 % Grens

T=180 s

PIANC 90-100 %

Figure 16: Relation period vs. handling rates

Note all lines represent surge motions.

From the graph above it is clearly seen that the velocity of motion has an influence onthe loading process. The velocity of motion is related to the amplitude and period ofmotion. The period of ship motion is related to the dimension of a vessel. A smallervessel has a lower response period than larger vessels. Thus smaller vessels are morelikely to encounter difficulties during unloading operations than larger vessels.

4.3.2 Comparison with PIANC

After these runs it is interesting to see how the results compare with the PIANC criteria.

The two vertical dashed lines in the graph above represent the criteria presented byPIANC. The vertical line through 0.5 m, on the x-axis, represents PIANC’s surgecriterion for undisturbed loading. This means that the overall handling rates aresomewhere between 90 and 100 percent of the average throughput. The upperhorizontal dashed line represents this 90 to a 100 percent handling rates. From the graph


it can be clearly seen that PIANC’s criteria are rather generous. According to the modelthe criterion for the undisturbed situation should be around 0.2-0.4 meters depending onthe period of oscillation, where PIANC advised 0.5 meter. In case of sway PIANCadvises a criterion of 0.3 meter, away from the berth. This is in accordance with presentmodel findings of about 0.2 m.

The second vertical dashed line represents the criteria from PIANC for the disturbedloading situation. In this case loading rated is around fifty percent of the averagehandling rates. The second horizontal dashed line represents this limit. It can be seenthat the criteria presented by PIANC are rather conservative for this situation. PIANCadvises motions of about one meter for surge where the model would give around 1 to1.5 meters, dependent on the period of motion. For sway motions PIANC advisedmaximal amplitude of around 0.6 meter while the model would suggest criteria of about 1meter.

Stricter criteria for combinations of motion

PIANC presented their criteria for pure surge or sway only. But from the runs madeabove it can be clearly seen that criteria for individual motions underestimate theachievable throughput in case of combined motions. So in the future it would be better topresent criteria for combinations of motions

4.4 Application of the model

From the test runs it is obvious that handling rates are dependent on the period ofoscillation as well as on the amplitude. Since vessels with different dimensions responddifferent to the same external force, presenting criteria that are universally valid for allcombinations of period and amplitude would not be the right thing to do.

The criteria may be used to verify whether a new design or an adjustment of an existingcontainer berth would meet the requirements of the client. For verification of a designone can use a moored ship computer model such as BAS, by Delft Hydraulics, orTermsim, by Marin to calculate the ship motions in reaction to environmental conditions.So why not add the model to the ship-mooring program. This way one can calculate theship motions, mooring line forces and the handling rates under the governing conditions.

This requires a simulation of the un-loading of a container ship. The simulation shouldcover the entire procedure from the arrival of the vessel till its departure. Furthermore,cycle times need to be as accurate as possible. These cycle times include therepositioning of the crane at a different bay, shift duration’s and crew changes, taking offthe hatches, twistlock removing/ placing, lashing but also the travelling times of acontainer in the cell guides of the vessel. It matters whether a container comes from thegreat depths of the hold or whether is comes from the deck. And again travel timeschange during the (un)-loading operation. Also the (un)-loading sequence is important,two possible sequences can be found in Figure 17. Then the developed model can beused for the calculation of the time needed for placement of individual containers. It is amatter of logical thinking and it may sound quite simple but there are a lot of elementsinvolved that require attention.


Figure 17: Loading sequence

Another important part when the model would be added to a mooring simulation programis the translation of the six possible motions of a moored vessel into three singletranslations. This translation has to be done separately for each location on the shipsince the effect of a rotation is directly related to the distance from that point to the centreof gravity of the vessel. See also Co-ordinate systems on page 8. This aspect requires alot more programming since a grid needs to be introduced and every spot on a containership needs to be given a co-ordinate. This could become quite complex since every shiphas a different geometry.

4.5 Possible improvements

As with every new model there are a number of items that could be improved. Thefollowing list presents an overview of future improvements.

- Ship motion

In the current model the PM-spectrum has been used to create an irregular vesselmotion. It is however questioned whether this spectrum can be used to describe mooredvessel motions. A first comparison with the spectrum generated by Termsim for amoored LNG carrier showed a nice resemblance but further research into this matter isbeing advised.

- Heave motion

The present model is capable of working with two horizontal motions. Vertical motion isnot yet part of the model although it should not be too difficult to implement it into themodel. In case of heave motions the crane driver cannot position the spreader/ containerdirectly above the cell guide. Instead he has to increase the height to prevent thecontainer from hitting the vessel. This means that the lowering distance in the model hasto be increased leading to a longer time span between the time the driver decides tolower the container and the arrival of the container at the cell guide. Unfortunately thereis no research available to calibrate vertical displacement in the model so this remains apoint of possible investigation.

8

7

6

5

4

16

15

14

13

24

23

32

22

31

40 154

132

110

88

66

155

133

111

89

156

134

157

112

135

158

Quay Quay


- Decision module

The decision module has been designed from scratch. The design is based on how itwas interpreted that a human would decide to do something or not. It could be wellpossible that for such problems there are better ways to build a decision module thatrepresents human action.

- Better programming, user friendly

The current model has been programmed in Mathcad, a math software utility like manyothers. The programming of the model is quite unfriendly at the moment. The layout andinput/ output fields are located within the program and this makes it quite unattractive. Itwould be better to reprogram the model in Delhi or some other compiler program and toimprove the ease of use.

4.6 Conclusion & Recommendations

4.6.1 Conclusions

- Calibration acceptable/ Good- The developed model clearly shows the decrease of the handling rates in relation to an

increase in amplitude or decrease of the period.- The first test results show that the criteria proposed by PIANC for the condition in

which 90 to a 100 percent of the maximum achievable throughput could be met are notstrict enough.

- The PIANC criteria for the fifty- percent handling limit are too strict.- Criteria need to be based on the ship size since the model clearly shows a relation

between the dominant period of motion and the handling rate. The dominant motion ofa vessel is dependent on her geometry, the way she is moored and the mooring layoutof the berth.

4.6.2 Recommendations

- It would be better to present the criteria with respect to a significant ship motion. Thedisplacement of a moored ship is never regular in time and it are not the averageconditions that limit (un)-loading operations but the significant motions. Therefore it issuggested to use the significant ship motions that represent the average of the highestone third of ship displacements.

- See Paragraph 4.5 Possible improvements.


5 QUESTIONNAIRE

Although the model calibration so far performed includes the influence of the humanfactor (through the tests of Slinn) the reliability of the model would be further enhancedwhen based on real findings from the loading of container ships. With this in mind aquestionnaire has been sent to harbour masters for their opinions. A letter ofrecommendation has been added to emphasise that the results of the questionnairewould be used in scientific research and not for commercial purposes.

5.1 Questionnaire

The following questions were listed in the questionnaire:

1. Does your terminal encounter difficulties during loading and unloading ofcontainerships due to excessive motion of the container vessel?

This question is meant to serve as a first filter since from the literature study itwas found that only people that have had experience with ship motion can givereliable criteria.

2. Please describe how these movements are produced (wave action along theberth , wave action perpendicular to the berth etc)

A question to find out if harbour masers would give different criteria for differentcauses

3. Have you done research into the loss of productivity with ship movements? If youhave, would you be able to make this research available to the study team?

Clearly intended to gather more information on the subject of reduced handlingrates due to ship motion.

4. Experience shows that quay crane productivity is likely to reduce as themovement of the landing site for the container or spreader increases. Do youhave any views on how much movement can occur before productivity issignificantly reduced?

The first real question about criteria for loading container vessels

5. Do you consider the size of the ship has a significant effect? Small vessels arelikely to have a more rapid motion than large ones.

From the model it followed that the period of motion has an effect on the reducedhandling rates. Since moored vessels can be regarded as a mass spring systemthe eigenfrequency is dependent on the stiffness of the mooring system and onthe mass of the ship. The mass of a ship is directly related to its size.


6. The table below sets out the current PIANC recommendations on acceptablevessel movements at container berths. Please give your views on the relativeimportance of each movement and whether the figures are realistic.

Most troublesome motion

on a scale of 1 to 6 (*)Ship motion

Proposed

criteria

Your opinion (**) Allowable motion in

your company (***)

Surge (m)1 1.0 m -2 -1 0 1 2

Sway (m)2 0.6 m -2 -1 0 1 2

Heave (m)1 0.8 m -2 -1 0 1 2

Rolling (°)1 1° -2 -1 0 1 2

Pitching (°)1 1° -2 -1 0 1 2

Yawing (°)1 3° -2 -1 0 1 2

Note: 1: Motions refer to peak-peak values

2: sway motions are zero peak

Components of ship motion:

Surge: Longitudinal motionSway: Transverse motion

Heave: Vertical motionRolling: Rotating motion around longitudinal axis

Pitching: Rotating motion around transverse axis

Yawing: Rotating motion around vertical axis

(*) Please give a rating to each ship movement that might cause trouble during loading and unloadingoperation. The number 1 corresponds to the most important motion, the number 6 is the least

significant motion.(**) Please circle the number that corresponds with your opinion. The numbers have the following

meaning:

-2 means that you think the allowable movements should be 0.5 times smaller than the proposedcriteria-1 means that you think the allowable movements should a little smaller than the proposed criteria0 means that you think that the proposed criteria are correct

1 means that you think the allowable movements should a little bigger than the proposed criteria2 means that you think the allowable movements should be 1.5 times bigger than the proposed

criteria

(***) Only fill in when your company has its own criteria for the allowable movements of container shipsduring loading and unloading operations. Please make it clear whether these are criteria relating to

loss of productivity or stopping work because it is unsafe to continue.


7. Does jamming of containers in cell guides occur at your terminal?

According to some scientists the loading of containers is hampered due tojamming of containers in the cell guides. This jamming is believed to be causedby the rotation of the guides, in other words, by roll and pitch motions. Thisquestion is meant to find out whether the harbour master has any experiencewith this phenomenon

8. Do you have any view on the cause of jamming? (roll motions, pitch motions,bent cell guides, bent containers, etc)

If people have indeed encountered the jamming of containers it is interesting toknow what they felt was the reason for jamming.

9. In theory jamming might occur due to rotations of the cell guides. Do yousubscribe this opinion and if so, can you give limitations for these motions?

This question is intended to find out if there is any support for the theory ofjamming due to roll and/ or pitch motions

10. Do you have rules giving maximum movement of the container or spreader“landing site” at which operations are suspended for safety reasons?

It seems logical that operations are suspended long before critical situations aremet due to safety of man and machine.

11. What other criteria do you have for suspension of operations because of adverseconditions (wind speed, heavy rain, safety of lashing gangs etc)?

More or less intended to find out what other reasons might be to cease loadingoperations.

5.2 Group of interest

The selection of harbours of interest to the questionnaire was made via theContainerisation International Yearbook. The main criteria for selecting a harbour werethe geographical location. Harbours located on the Atlantic coasts are more likely toencounter swell waves, i.e. Ponta Delgada in the Azores. Also harbours were selectedthat are known for there problems with long wave phenomena, i.e. Port Elizabeth inSouth Africa and Long Beach, USA.

In total twenty-nine harbours were selected to receive the questionnaire. The total list ofharbours can be found in the appendix.

5.3 Results

From the twenty-nine questionnaires sent, only two useful questionnaires were returned.

Altogether the sending of twenty-nine questionnaires resulted in two usable responses.Although disappointing, it might have been expected. The Ports and Harbours ResearchInstitute (Ueda and Shiraishi 1988) only received 20% response on a similarquestionnaire (Section 3.4.3).


The low return rate implies that no decisive conclusions can be drawn from the filled inquestionnaire. Still, the two results will be discussed here.

- Both the terminals encounter difficulties during loading during adverse weatherconditions. The main cause are swell waves both perpendicular and along theberth. Although they encountered problems no research into the subject has beendone by the harbour masters, so they can’t share that information with the researchteam.

- Both terminals noticed that the amount of handling reduction is related to the shipsize.

- With regard to the criteria there is mutual agreement that the criteria for surge,sway and heave should be much stricter than the criteria presented by PIANC.

- The criteria for roll and pitch are considered just fine and there is a slightdisagreement on the yaw criteria. One harbour master finds the criteria just finewhile the other thinks is could be a bit stricter.

- The fact that they consider the criteria for rotation to be good and the criteria fortranslations not strict enough can be explained by the following part.

- In question seven they both answer that occasional jamming of containers occurs.The main reason for jamming is considered to be bent containers and damaged cellguides. However they do not subscribe the vision that jamming is caused by therotation of the cell guides due to roll and/or pitch. This theory was introduced byd’Hondt (d’Hondt 1999). More information about this theory can be found inparagraph 3.2.5.

- The decision to suspend loading operations can be made by the crane operatorand the marine supervisor on duty and is based on experience. The main reason totemporarily suspend operations is heavy winds.


6 CONCLUSIONS AND RECOMMENDATIONS

When designing a new container terminal it is necessary to know how much ship motionis allowable under normal conditions. The allowable ship motion determines the amountof protection that is needed for the berth. This research project has been initiated to findthese criteria for (un)-loading containerships. To establish these criteria the focus of thisstudy has been on finding a relation between the motions of the vessel that is (un)-loaded and the handling rates. After an intensive investigation into the matter thefollowing findings have been reached:

• To study the subject in detail a working computer model has been developed thatcalculates the effect of (bay) motions on container throughput

• The model allows to study the (implicit) impact of wave height as well as wave periodon the container throughput by including irregular, time varying bay motions

• The model has been calibrated using available data which importantly includes the"human factor". The calibration results show to be very good.

• The model describes the reduced throughput as a function of increased bay motionson a continuous interval.

Using the developed model a number of conclusions can be drawn with respect tocurrent motion criteria and the effect of irregular (bay) motions on the containerthroughput:

• A relation has been found that directly relates handling rates to ship motions• Apart from the amplitude of motion also the period of motion influences these

handling rates. Slower (bay) motions give the crane driver a better chance tocorrectly place a container.

• In case of combined surge and sway, handling rates drop faster than in case of(pure) surge or (pure) sway

• The current criteria as presented by PIANC for (pure) surge or (pure) sway appearnot strict enough for the undisturbed loading rate (90/100% throughput)

• On the other hand the PIANC criteria for (pure) surge or (pure) sway for the 50percent loading rate appear too strict

• PIANC does not provide criteria for (combined) surge and sway. Adopting the criteriafor (pure) surge or (pure) sway in a situation with combined motions appears notstrict enough.

• In due course of the project it became clear that handling rates are not influenced bythe jamming of containers in the cell guides due to roll and/or pitch.

Furthermore the following recommendation is done:

• It is advised to make runs for three different representative vessels, e.g. a feeder, a4th generation container ship and a jumbo vessel. The goal of these runs is to seehow the efficiency of the loading process differs for different ships since each shiptype responds different to the same environmental conditions.

With the presently developed model in principal a method is available to relate containerthroughput to ship motions. However it is to be recognised that the model is still in itsinitial phase of development and that further developments would be required to make


this model a useful tool. For this future development the following modifications arerecommended:

• The model may be expanded to include all six degree of freedom of the vesselmotions into the projection of the bay to a horizontal plane (where the container hasto fit in)

• The calibration may be improved by repeating the tests done by Slinn, sinceimprovements in modern container crane technology might prove the Slinn results tobe outdated. An option to this may be to take advantage of modern container cranesimulators used to train container crane operators.

• Improvement of the decision module/uncertainty factor. The calibration of the modelhas mainly been achieved through the uncertainty factor in the assessment of theposition of the container. The decision module appeared to have a relatively smallimpact on the calibration. Therefore it appears that the combination decisionmodule/uncertainty factor may be subject for further (re-)analysis.

• Although not addressed in this study, also the container in the spreader and theheadblock will be moving. Hence, the model may be further improved byimplementing the motions of the container in the spreader although this is assessedto be a complex task.

• To verify the results of the model, results from the "real world" remain indispensable.Despite the disappointing response on the questionnaire sent out, still aquestionnaire issued on a large scale to obtain the opinions of harbour mastersregarding the subject is highly recommended. Preferably this questionnaire shouldbe done under the umbrella of an organisation such as PIANC

Eventually, a model developed along these lines and linked to a Six Degree of Freedommodel for ship motions, may result in a tool which would be able to simulate the timerequired to load a container vessel including the effects of the movement of the vessel oneach individual bay.


7 REFERENCES

August Design Inc, (2001), “Advanced robotic crane for container handling”,http://pages.prodigy.com/AUGUST/aacts.htm

Bloom, M., Posch, A. (1980), “Container ship motion criteria”, The Dock and HarbourAuthority.December 1980, pp. 260-262.

D’Hondt, E. (1999), “Port and terminal construction: design rules and practicalexperience”, 12th Int. harbour congress, Antwerp.

“Development in container handling technology”, chapter 2.1 Ship to shore cranes.

Gerstel, A.W., (2000), “Container cranes for 8000 TEU and larger vessels”, DelftUniversity of Technology.

Hou, H.S., Weng, G.H, (1987), “Physical model test of the moored containership motionand the related induced mooring force”, Twentieth Coastal Engineering Conference, pp.2723-2734.

Huisman, J.M, Ouden, den, D.J.J.(2001), “Grote containerschepen”, Schip en Werf deZee, april 2001, pp. 5-11.

ISO 668-(1988), 830-(1981), 1161-(1984) ISO Standard Handbook, Freight Containers

Jensen, O.J., Elzinga, Th., Iribarren, J.R. (1992), “Movements of moored ships inharbours”, Coastal Engineering 1992, pp. 3216-3229.

Jensen, O.L., Viggosson, G., Thomsen, J., Bjorndal, S., Lundgren, J., (1990), “Criteria forship movements in harbours”, 22nd Coastal Engineering Conference, Delft, Netherlands,pp.3074-3087.

Ligteringen, Prof. H., (2000), “Ports and Terminals”, lecture notes CTwa4330/ 5306 DelftUniversity of Technology.

Mangoon, Orville T. et al, (1989), “Ship motions moored at quay walls and their effectsto wharf operation efficiency”, coastal zone’89.

Mattews, S. J., (1989), “Advances in container handling technology”, PIANC bulletin nr.66, pp. 72-79.

Nam, K.I. and Ha, W.I. “Evaluation of handling systems for container terminals”, journalof waterway, port, coastal and ocean engineering.

PIANC working group 24, (1995), “Movements of moored ships at berth, section 9Container ships”.

PIANC working group 24, (1995), “Criteria for movements of moored ships in harbours”,Supplement to PIANC bulletin 88.


Pierson, W.J., Jr. and L. Moskowitz, (1964),”A proposed spectral form for fully developedwind seas based on the similarity law of S.A. Kitaigorodskii”, Journal Geophys. Res., Vol.69, No. 24, pp. 5181-5190

Poon, Y.K., Walker, P.E., Headland, J. (1998), “Alternative mooring and fender design toreduce container ship motions”, Ports ’98, pp. 880-889.

Raichlen, F., Poon, Y-K, Dean R G. (1999), “The role of harbour resonance in portoperation” COPEDEC V, Cape Town SA, pp.540-551.

Sarneel, J., (2000). “The analysis of model measurements concerning the behaviour ofmoored ships in long waves”, MSc thesis, Delft University of Technology.

“Survey container cranes, A global outreach” (2000), Port Development InternationalMagazine march 2000

Slinn, P.J.B., (1979), “Effect of ship movement on container handling rates”, The Dockand Harbour Authority, August 1979, pp. 117-120.

TRAIL research school, “De high performance elevator crane”, De terminal van detoekomst.

Ueda, S. and Shiraishi, S. (1988), “The allowable ship motions for cargo handling atwharves”, Report of the Port and Harbour Research Institute, vol. 27, no 4, pp. 3-61.1988.

Ueda, S., Shiraishi, S., (1989), “Ship motions moored at quay walls and their effect onwharf operation efficiency”, Coastal zone ’89, pp. 2271-2285..

Vickerman, W., (1989), “Intermodalism: setting new criteria for U.S. container terminaldesign and operation”, PIANC bulletin 1989 no 67, pp. 98-105

Wang, S., (1975), “Dynamic effects of ship passage on moored vessels”, Journal ofWaterways Harbours and Coastal Engineering Division, pp. 247-257.


APPENDICES

Appendix 1: Research Assignment

Research Programme Behaviour of Moored ShipsProject: Criteria for (un)loading container shipsDraft Scope of Work (20 February 2001)

1. Introduction

The Research Programme BMS has been initiated by TU-Delft, Fac. CITG,Section of Hydraulical Engineering, in 2000. The main objective is to improve theunderstanding of the response of moored ships to (long) waves, and to developpractical tools for the prediction of the downtime of a ship at berth, to be used inearly stage of port lay-out development. A second objective is to use availabledata of waves and ships motions/mooring time forces, measured in prototype orin models, for the verification of existing numerical models. The project "Criteriafor (un)loading of container ships" is one of the sub-projects within the BMSProgramme. Such criteria are needed for the down time analysis.

2. Problem description and project objective

Limiting conditions for (un)loading of different types of ships have been publishedin literature (Bruun, 1989). An overview of existing experience was most recentlypresented by the Report of PIANC, Working Group no 24 (PIANC. 1995). Most ofthe criteria presented are considered reasonable, based on many years ofexperience in the handling of tankers and dry bulk vessels. The criteria forcontainer ships are questioned by industry and likely to be outdated by the rapidgrowth of these ships.The objective of the project is to update the motion criteria for container ships,based on computations, feed-back from practice and possibly model test. Ifdesirable the new criteria may be presented as a function of ship size.

3. Outline methodology

After review of available literature on the subject, the following steps areproposed:

(i) Familiarisation with crane operation procedures in practice.(ii) Investigation of operational limitations at existing terminals (probably by

visits to relevant terminals in NW-Europe).(iii) Analysis of limiting conditions, based on the operational experience and

computations (e.g. friction forces in cell guides caused by roll and/or pitchmotions, vertical movements of the bow and stem holds due tot heave andpitch, etc.).

(iv) Report on the result with provisional conclusions regarding new criteria, andrecommendations on future research, including possible model test.


Appendix 2: Program Listing


Appendix 3: Returned Questionnaires

Questionnaire number 1

Please note that a digital version is available at www.waterbouw.tudelft.nl/questionnaire/Filled in Questionnaires can be mailed to [email protected], faxed to 015-

2785124 or send by mail to the address mentioned on the accompanying letter.

1. Does your terminal encounter difficulties during loading and unloading of containerships due to excessive motion of the container vessel?

No, except during bad weather

2. Please describe how these movements are produced (wave action along the berth,wave action perpendicular to the berth etc)

Wave action perpendicular to the berth

3. Have you done any research into loss of productivity with ship movements? If you

have, would you be able to make this research available to the study team?

No

4. Experience shows that quay crane productivity is likely to reduce as the movement ofthe “landing site” for the container or spreader increases. Do you have any views on

how much movement can occur before productivity is significantly reduced?

No

5. Do you consider that the size of ship has a significant effect? Small vessels arelikely to have a more rapid motion than large.

Yes


6. The table below sets out the current PIANC recommendations on acceptable vesselmovements at container berths. Please give your views on the relative importance of

each movement and whether the figures are realistic.

Most troublesome motion on ascale of 1 to 6 (*)

Ship motionProposedcriteria

Your opinion (**) Allowable motion inyour company (***)

Surge (m)1 1.0 m -2 -1 0 1 2

Sway (m)2 0.6 m -2 -1 0 1 2

Heave (m)1 0.8 m -2 -1 0 1 2

Rolling (°)1 1° -2 -1 0 1 2

Pitching (°)1 1° -2 -1 0 1 2

Yawing (°)1 3° -2 -1 0 1 2

Note: 1: Motions refer to peak-peak values2: sway motions are zero peak


Surge: Longitudinal motion

Sway: Transverse motionHeave: Vertical motion

Rolling: Rotating motion around longitudinal axisPitching: Rotating motion around transverse axis


(*) Please give a rating to each ship movement that might cause trouble during loading and unloading

operation. The number 1 corresponds to the most important motion, the number 6 is the leastsignificant motion.

(**) Please circle the number that corresponds with your opinion. The numbers have the following

meaning:-2 means that you think the allowable movements should be 0.5 times smaller than the proposed

criteria

-1 means that you think the allowable movements should a little smaller than the proposed criteria

0 means that you think that the proposed criteria are correct


criteria(***) Only fill in when your company has its own criteria for the allowable movements of container ships

during loading and unloading operations. Please make it clear whether these are criteria relating to




Sometimes, once a month

8. Do you have any view on the cause of jamming? (roll motions, pitch motions, bentcell guides, bent containers, etc)

Bent containers, cell guides in bad shapes

9. In theory jamming might occur due to rotations of the cell guides. Do you subscribe

this opinion and if so, can you give limitations for these motions?

No

10. Do you have rules giving maximum movement of the container or spreader “landingsite” at which operations are suspended for safety reasons?

At the discretion of the crane operator and marine supervisor on duty

11. What other criteria do you have for suspension of operations because of adverse

conditions (wind speed, heavy rain, safety of lashing gangs etc)?

Wind speed. Heavy rains, thunder storms, earthquake, etc

End


Questionnaire number 2

Please note that a digital version is available at www.waterbouw.tudelft.nl/questionnaire/Filled in Questionnaires can be mailed to [email protected], faxed to 015-

2785124 or send by mail to the address mentioned on the accompanying letter.

1. Does your terminal encounter difficulties during loading and unloading of containerships due to excessive motion of the container vessel?

One berth in adverse weather conditions from one particular direction, difficulties areencountered during loading and unloading of container vessels (feeders) of less than 150meters LOA. So far, no such problems were found with Panamax and post Panamaxships.

2. Please describe how these movements are produced (wave action along the berth,

wave action perpendicular to the berth etc)

Vessel movements were produced by residual wave/ swell action along the berth

3. Have you done any research into loss of productivity with ship movements? If youhave, would you be able to make this research available to the study team?

As such occurrences are small, no research into the loss of productivity with ship

movements has been carried out.

4. Experience shows that quay crane productivity is likely to reduce as the movement ofthe “landing site” for the container or spreader increases. Do you have any views on

how much movement can occur before productivity is significantly reduced?

It is difficult to measure ship motions with any degree of certainty when quay craneproductivity starts to fall. When loading and unloading become unsafe, the operations are

temporarily terminated. These are however subjective decisions based on personalexperience.

5. Do you consider that the size of ship has a significant effect? Small vessels are

likely to have a more rapid motion than large.

Yes, small vessels have a more rapid motion than large vessels


6. The table below sets out the current PIANC recommendations on acceptable vesselmovements at container berths. Please give your views on the relative importance of

each movement and whether the figures are realistic.

Most troublesome motion on ascale of 1 to 6 (*)

Ship motionProposedcriteria

Your opinion (**) Allowable motion inyour company (***)

Surge (m)1 1.0 m -2 -1 0 1 2

Sway (m)2 0.6 m -2 -1 0 1 2

Heave (m)1 0.8 m -2 -1 0 1 2

Rolling (°)1 1° -2 -1 0 1 2

Pitching (°)1 1° -2 -1 0 1 2

Yawing (°)1 3° -2 -1 0 1 2

Note: 1: Motions refer to peak-peak values2: sway motions are zero peak


Surge: Longitudinal motion

Sway: Transverse motionHeave: Vertical motion

Rolling: Rotating motion around longitudinal axisPitching: Rotating motion around transverse axis


(*) Please give a rating to each ship movement that might cause trouble during loading and unloading

operation. The number 1 corresponds to the most important motion, the number 6 is the leastsignificant motion.

(**) Please circle the number that corresponds with your opinion. The numbers have the following

meaning:-2 means that you think the allowable movements should be 0.5 times smaller than the proposed

criteria

-1 means that you think the allowable movements should a little smaller than the proposed criteria

0 means that you think that the proposed criteria are correct


criteria(***) Only fill in when your company has its own criteria for the allowable movements of container ships

during loading and unloading operations. Please make it clear whether these are criteria relating to




Yes

8. Do you have any view on the cause of jamming? (roll motions, pitch motions, bentcell guides, bent containers, etc)

Bent cell guides or damaged corner castings of containers

9. In theory jamming might occur due to rotations of the cell guides. Do you subscribe

this opinion and if so, can you give limitations for these motions?

No experience of jamming due to ship motions

10. Do you have rules giving maximum movement of the container or spreader “landingsite” at which operations are suspended for safety reasons?

The decision to suspend operations for safety reasons due to ship motions is based on

operator’s experience.

11. What other criteria do you have for suspension of operations because of adverseconditions (wind speed, heavy rain, safety of lashing gangs etc)?

Crane operations stop automatically when wind speed exceed manufacturer’s specified

wind speed.

End


Appendix 4: Addresses of the questionnaire

County Location Address Telephone/ e-mail

Australia Fremantle Fremantle Port AuthorityAtt. Mr. Kerry Sanderson1 Cliff StPO Box 95FremantleWA 6160Autralia

+61894304911

Australia Newcastle Newcastle Port CorpAtt. Mr. Garry WebbCnr Scott & Newcomen St.PO Box 663NewcastleNSW 2300Australia

+61249858222

Azores PontaDelgada

Junta Autonoma do porto de PontaDelgadaAtt. Mr. Jose Manuel Pacheco CostaPO Box 1139502 Ponta DelgadaSao MiguelAzores

+35196285221

Brazil Suape Suape Complexo IndustrialPortuarioAtt. Mr. Gilberto BarretoComplexo Industrial de SuapeKm 10, Rod PE-60Engenho Massangana-IpojucaCEP 55590-000 RecifeBrazil

+5581527110

Canada Vancouver TSI Terminal Systems IncAtt. Mr. Barrie Sime2 Roberts BankDeltaBC V4M 4G5Canada

+16042155700

Canary Islands Las Palmas Leon y Castillo DockAtt. Capt. Juan PerezOperaciones Portuaries Canrias SaMuelle Leon y Castillo, WestE-35008 Las Palmas de GranCanariaGran Canaria, Canary Islands

+34928300666


Chile Antofagasta Empresa Porttuaria de ChileAdministracion del PuertoCP 190 AntofagastaChile

+5655223587

Chile San Antonio Empresa Portuaria de ChileAtt. Mr. Daniel Rojo VasquezAdministracion del PuertoCassila 163-A Alan Macowan0245 San AntonioChile

+5635212159

Chile Valparaiso Empresa Portuaria de ChileAtt. Mr. Particio Toro FerrariCasilla 25-VValparaisoChile

+5632257167

DominicanRepublic

Rio Haina CSX Terminls IncAtt. Mr. Jose N. GonzalesPuerto de Haina OccidentalPio HainaDominican Republic

+18095422591

India Tuticorin Tuticorin Port TrustAtt. Mr. M.J. KurienBharathi NagarTuticorin 6280004India

+91461352290

Ireland Cork Port of Cork CoAtt. Mr. Sean J. GearyHarbour Office, Customs house StPo Box 53Cork, Co CorkIreland

+35321273125

Italy Gioia Tauro Port of Gioia TauroAtt. Mr. Francesco CostaMedecenter Container terminalArea PortoI-89013 Gioia Tauro RCItaly

+3909667141

Italy Genoa Voltri terminalAtt. Mr. Dino CanaliPalazzina UfficiI-16158 GenoaItaly

+390106996508

Malta Marsaxlokk Freeport terminal Ltd.Att. Mr. Marin HiliFreeport centrePost of MarsaxlokkKalafrana BBG 05Malta

+356650200


Norway Bergen Bergen og Omland HavnevesenAtt. Mr. Max KarlsenSlottsgate 1N-5003 BergenNorway

+4755568950

Seychelles Port Victoria Land Marine LtdAtt. Mr. Patrick R. BarallonPO Box 38New Port, Victoria, MaheSeychelles

+248224624

South Africa Port Elizabeth PortnetAtt. Mr. E.H.E. HillPO Box 162Port Elizabeth 6000South Africa

+27415072604

South Korea Pusan Pusan East Container Terminal CoLtdAtt. Mr. Byung Sung123 Yongdang-dongMan-guPusanSouth Korea

+82516218111

Spain Algeciras Mearsk Sealand Espana SAAtt. Mr. Jorgen D NielsenApartado 160E-11201 AlgecirasSpain

+34956671900

Sri Lanka Colombo Sri Lanka Ports AuthorityAtt. Mr. H.A. Wijegunawardhana19 Church StPO Box595Colombo01Sri Lanka

+941421201

Tanzania Dar-es-Salaam

Tanzania Harbours AuthorityAtt. Mr. Samson LuhigoPO Box 9184Dar-es-SalaamTanzania

+255222110401

Trinidad &Tobago

Point Lisas Point Lisas Industrial PortDevelopment Corp ltdAtt. Capt. Rawle BaddalooAtlantic AvePoint Lisas Ind EstPort of SpainTrinidad & Tobago

+18686364913


United Kingdom Felixstowe Port of FelixstoweAtt. Mr. Chris GrayTomlime house, the dockFelixstowe, Suffolk IP11 3SYUnited Kingdom

+441394604500

USA Long Beach Mearsk Sealand/ CSX Service IncAtt. Mr. Dick Carthas840 Harbour PlazaPO Box 1251Long BeachCA 90801USA

+15624327411

USA Long Beach Hanjin Shipping Co ltdAtt. Mr. Kevin Nicolello700 Hanjin WayLong BeachCA 90813USA

+15629512503

USA Long Beach Pacific Container Terminal IncAtt. Mr. Sal Ferrigno871 Harbor Scenic WayLong BachCA 90802USA

+15624350842

USA Seattle Stevedoring Services of AmericaAtt. Mr. Lee MacGregor1131 SW Klickitat WaySeattleWA 98134USA

+12066543707

USA Los Angeles APL ltdAtt. Mr. Jeff Grahovec614 Terminal WayTerminal IslandSan PedroUSA

+13105488700

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