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CONCERNS OF SHIP OPERATORS Lincoln Crane, Jr. Basic Requirements at a Harbor Entrance The three succeeding presentations address aids to navigation, ship controllability, and pilots' concerns. My topic is ship operators' concerns. While linked to the other subjects, operators' concerns can be surveyed most simply with two questions: 1. 2. Does the harbor entrance provide sufficient horizontal (i.e., bank-to-bank) clearances under nonextreme conditions of wave, wind, and current? Is there sufficient bottom clearance under the nonextreme conditions? Answering these questions requires understanding the effects of a number of port-related factors, such as: . Horizontal channel dimension (i.e., channel segment widths, and lengths and radii of bends), Channel depths, Regularity of bottom and banks, Water waves, Strength and uniformity of water currents, and Quantity and quality of information provided to the shiphandler regarding ship's position relative to all the above. This list assumes that the ship has adequate inherent controllability, shipboard aids to navigation, machinery, communications, pilotage, and crew, all of which are outside the scope of harbor entrance design. Also assumed are adequate vessel traffic services and adherence to rules of the road. Port Appraisal Methods for Harbor Entrances How then can a ship operator objectively appraise a port to determine its suitability for a ship having particular dimensions? For horizontal clearances, he may take one of the following approaches: 45

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46 1. He may transfer previous harbor entrance experience to his new situation. In other words, he may follow his own or industry practice at a similar port. Or, he may use previously documented channel design standards such as are available from PIANC*, the U.S. Army Corps of Engineers, and the Canadian Coast Guard. l/2/3 However, these codes may not address the particular local issues in question, such as a locally high crosscurrent. Also useful may be the results of available ship-tracking studies made during port entry or departure, such as data taken at Southampton, Le Havre, and New York. 4/5/6 2. Another option is to order a specie' hydraulic model study of specific port-entry situations, such as those involving large and variable currents, maneuvering at bends, and breaking waves at an entrance. 7 3. Only in the last few years have real-time computer-based ship handling simulator studies become available, which include hands-on control by experienced ship handlers. Examples are recent studies conducted with large researab simulators, such as those of the Netherlands Ship Model Basin, 8 CAORFt,9 and the Swedish Maritime Research Center.~ All such large facilities offer outside-view displays combined with carefully duplicated wheelhouse mockups, shipboard navaids, etc. A number of less expensive real-time research simulators have recently been developed that employ cathode-ray-tube perspective scenes instead of outside views. These are supplemented with computer-graphic bird's eye displays that plot shoreline, aids to navigation, and the ship at closely spaced intervals. Under some circumstances, these simulators may satisfy all requirements, such as for appraising a new port-entry proposal relative to an acceptable base case. A much faster and less expensive technique is also now in use that simulates the ship handler's actions by substituting an automatic control function mathematically. Such a function must account for the key cues and sensitivities of human pilots. Figure 1 illustrates the functions that a human ship handler performs when piloting a vessel, and that simulation of the ship handler must also supply to an appropriate degree. The full computer simulation is clearly limited to rather simple navigational situations, and in those, it has the advantage of allowing numerous orderly variations of main parameters. Examples are studies of the effects of changes in the direction and magnitude of disturbances such as wind and current.9 6. Methods of direct calculation have been applied in some harbor- entrance design projects, such as in the selection of approach- channel widths and aids to navigation at the new port for ultralarge crude carriers (ULCC) at Cape Antifer, near Le Havre. In that case, the Maximum variation" method developed by EASAMS, Ltd., of the U.K. was used (described by M. Ribadeaux Dumas in *Permanent International Association of Navigational Congresses Computer-Aided Operations Research Facility

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47 ESTI MATED ACTUAL WIND CURRENT. ACT UA L LY RE SU LTING ACTUAL WIN D _ CU.R RENT E-8-8 0-28 HUMAN E ST I MATING ELK MENT L ............... J Z 2 LLI ~ 2 ~ ~ lY _ I 1~ l o ~ SHIP DYNAMICS l ...... ' ~ ~............ ~'~ . POSITION SPEED HEADING _ TURNING RATE WIND . ~ l CURRENT ORDERED RUDDER ANGLE PROPE LLER - REV.S F. ~ Isure 1 MAN- SH I P CONTR OL LOO P HUMAN MOTION PREDICTING INTERNAL MODEL . ,.............................. _ - tY PREDICTED 2 FUTURE ~' ,_ ~ z 2 ~n o ~ ~ ~ ~ ~ \ I _ , _ . _ _ HUMAN DECI SION MAKING E LE MENT ___..._.,. . , ~ PREDICTED FUTURE WIND , CURRENT TRAFFIC ~Tr , ~ ~.

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48 reference 11~. This method estimates the maximum variation of a vessel from its intended track due to the navigator's uncertainty of his position. The resulting overshoot motion of the ship in recovering and returning to the channel centerline is estimated in a paper analysis. Turning now to bottom-clearance appraisals, there is again more than one available procedure. The simplest is, of course, direct local knowledge based solely on the experience of earlier ships In that area and the reports of pilots. Regarding analysis, the basic calculation is simply to subtract the ship's static draft at its lowest point from the calculated water depth at the shallowest spot.t Allowances are then made for ship sinkage and trim at speed, possible heel, ship motions in waves, tidal height, and bottom siltation and debris, as shown in Figure 2a. However, this calculation will produce overly conservative results because it assumes the coincidence of maximum excursions if simple algebraic addition of allowances is used. Therefore, statistical addition of allowances for each factor should be substituted (Figure 2b). In very special cases, model or full-scale ship trials may be made to determine actual bottom clearances. This was recently done for the National Ports Council by the National Maritime Institute in England for ships entering Southampton, and for ships passing over the bar at the Columbia River entrance in Oregon. Indices Having predicted the horizontal and vertical ship-to-ground clearances, the operator will want to complete his appraisal by comparing the results to some standards. If results are positive, he may judge the port to be safe. For horizontal clearance, the index should address the minimum bank clearances at the most critical points, such as: Where a ship is held close to one bank prior to entering a turn, or when preparing for an abrupt shear-current effect from that side; Where a ship is recovering from a turn in the channel, or after responding to a shear current; Where a ship's controllability is reduced by the need to decrease speed (hence, propeller rpm and rudder force); Where the ship normally passes other ships in a channel. To judge the maneuvering safety of the candidate ship, the operator must then compare its expected performance against that of a base ship with which he is presently comfortable in the same situation. For vertical (bottom) clearance the index will either be in terms of expected minimum bottom clearance (assuming that all anticipated clearance allowances are required at the came moment), or the probability of the ship's bottom coming within some small fixed distance of ground, say once in every "n n passages.

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49 WATER RE FER EN CE LEVE L G ROSS UNDERKEEL CLEARANCE AD Ml SSABLE DRAFT I VERTICAL MOTION J(SWELL AND SQUAT) _ _ _ _ _ _ _ ~ _ ~ NET UNDERKELL CLEARANCE NO MINAL CHANNEL BED LEVEL ~ - SOUNDING ACCURACY SEDI MENTATION BETWEEN DREDGINGS TOLERANCE FOR DREDGING F;9Ure 2a E-8-80-26 E-8-80-27 CONVENTIONAL NET BOTTOM CLEARANCE CALCULATION DEFINITIONS (FRO M PIANC RE F. 1) ~ - PREDICTED TIDE - _ _ _ CHARTED DEPTH ~ TIDAL UNCERTAINTY CHART DATU M ~i _ SHIP . ~=WATER LINE STATIC DRA FT STATIC DRAFT UNCERTAINTN SQUAT: J SQUAT CHARTED DEPTH - .~i-~.~4 UNCERTAINTY \ NOMINAL SEABED ~ UNDERCUT ~, ;, _ _ _ _ ~ ~W. VE RESPONSE S ILTAT ION . Figure 2b STATISTICAL BOTTOM CLEARANCE CA LCU LATION - DEFIN ITION S

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50 Limitations of Present Study Methods Several methods for appraising the adequacy of horizontal and vertical clearances have been mentioned here, yet none is entirely adequate for determining required channel clearances, either horizontal or vertical. Each has limitations. Tables 1 and 2 briefly reflect my personal views on the main strengths and limitations of each of the methods discussed above for horizontal and vertical clearances. ~ hope that these comments fairly reflect the problems of a ship operator when assessing how wide and how deep a harbor entrance must be for a particular vessel. References 2. 1. PIANC International Commission for the Reception of Large Ships {ICORELS), Working Group No. 4, "III. Recommendations Concerning Approach Channels and Maneuvering Areas for Large Ships, n November 1977. U.S. Army Corps of Engineers, Committee on Tidal Hydraulics, "Evaluation of Recent State of Knowledge of Factors Affecting Tidal Hydraulics and Related Phenomena, n C. F. Wicker, Editor, Report No. 2, May 1965. Canadian Coast Guard, Code of Recommended Standards for the Prevention of Pollution in Marine Terminal Systems n (TERMPOL) February 22, 1977. 4. Wride, A.T.A., A.E. Wills, and Leckenby, "Behavior of Large Ships in Shallow and Confined Waters (Southampton) n (NPL Report Mar Sci R121), 1975. Ribadeau-Dumas, L., "Antifer Aids to Navigation and Channel Maneuvering Experimental Results," Proceedings of Symposium on Aspects of Navigability of Constraint Waterways, Including Harbour Entrances, Delft, 1978. 6. Eda, H., R. Falls, and D. A. Walden, "Ship Maneuvering Safety Studies, n Transactions SNAME, 87 (1979~. . Boyleston, Je We, "Is Port Study Model Testing Really Worthwhile?" SNAME Marine TechnologY' January 1974 e Keith, Ve Fe, JeDe Porricelli, JePe Mooft, PeJ. Paymans, and FeG.J. Witt, "Real-Time Simulation of Tanker Operations for the Trans-Alaska Pipeline System,. Transactions S NAME, 85 (1977~. 9. Riek, J., S. Tenenbaum, and W. McIlroy, "An Investigation into Safety of Passage of Large Tankers in the Puget Sound Area" (National Maritime Researab Center Report No. CG-D-79-7S), 1978. 10. Nortbin, N. H., "Theory and Observation on the Use of a Mathematical Model for Ship Maneuvering in Deep and Confined Waterer (SSPA Publication No. 68), Gothenburg, 1971. 11. Ribadeau-Dumas, L., "Maximum Deviation Method, Proceedings 9th Conference of IALA, Ottawa, 1975. . 3. 7. 8.

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51 TIBLE 1 - STRIDIGTES/LDIIT1TIONS OF ~T9ODS FOR ESTh~TING lIIII~ ~ CLE~JICE IN HIRBOR E IITRANCE t~$E}OD STRDIGTElS LIMIT1TIONS 1~P}IRIIDIC11 TRlII~R Speciti Situations Design Guidolines, e.g., PIlIIC, COE, T1 - POL Direct evidenae without aodellng or alculating tor verlr siailar situations. Reprasant dlatillations o, quantitie~ of "perlonae. Not belptul tor extrapolation to ditterent altuations or to great ch~s of aalc. Do not address local pecullaritie-, and tend to be conservati~re for dealgn purpoaea. r "DRIUL1C tllDD&S Good repr - entation of b~lc and botta0 irr~ularitles and lo~r apeed ship ontrol tru - . "te. Very high ost and time requir~nts. So~e aodel-ship acale ettets in hydrodynauica and hu~n ontrol areas. R"L-TII. ~IIP"IIDL=G SI-LITORS ~lith Outdde Yi~r 1 Ulthout Outaide Yi~ Good repr~antation ot hu~n ontrol r~ sponses including variations. Conditions ~ily changed. 1count tor hu~n ontrol respons" in- ludiDg ~r4atloDs. Conditions ~ily h~ed. Moderate cost. High cost and ti~ requir~nta. Math aodel~ not yot validated tor irr~ular bottoa, banics, and current et~cta. As abo's regarding ~th aodele. Also, adequay of hu~an ontrol respona.e has ,et to bc validated. FAST-TIT- SllIP~DLIIIG ~lL1TIOII - Incspo~ivo, "d allo~ gr~t flosibility in studyint ettects of ch~yes ot pro~ bl" p~tere. As above regerding ~th aodels. In addition, asth aDdelling o, huran re~ponses ha~ ,et to bc ~lidated. DIlt8CT CILCIJLATION (~.B., H~ larlation llothod) In~lvo u~d quiolc tor deplo l~ding- li" t~ o, probl~. Ilot ~ppliablc to irregular bottoe or banlc, or to "nouvore with larg. transiente. ~. TABLE 2 - STRENGTES/LI=TATIONS OF Ml=}ODS FOR ESTIMATING REQUIRED STATIC BOTTOM CLEIRJUICE IN HAR90R ENTRANCE ttEl~OD STREIIGTEIS LIMITATIONS LOCIL "PERIEIICE Direct evidence, once [ully aquired. Takoa ti~o to de~relop tor a ne~r port, and can bo costly if early eati~tes are inadequate or over-con~errative. 1 1 1 TRlDITIONdL ALGEBR1IC ~ 0F ~ON"C" Errs on "to side. Also, allo~r~ s~ relati~c ca~rison trae port to port. Overconeer~rative. Ass~e all ~i~ ~ralues occur sienltaneoualy. T _ =ISI=ICIL S1111 OF ILLO"IIC1CS Realistially coebinos allo~n~. Roquires suttici~t data tor atati~tical *~_ tion o, uncertainties of all [actora. Presently liaised regarding ahallow water wave ~pectra and r~po~ue a~plitudo operators tor varioua ship types.

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52 DISCUSSION SEARLE: You have all the makings of a systems design, but it has become apparent to me over many years of casualties that you aren't playing the other part of the systems design game, and that is, the modes of failure, or hazards analysis. Now, the pilots know what I am talking about. The pilots will very quickly realize or come to learn in the Houston Ship Channel, for instance, two ships must not pass on suab and suab a bend. The National Transportation Safety Board begins to analyze accidents, and they notify the coast Guard to tell the pilots that they shouldn't pass there, but the people who designed the port, the channel, didn't put a note on the plan that says ships should not pass on that bend. They did not do the failure mode and effects analysis or the hazards analysis. They didn't do that part of the systems design that deals with "what if. n I ask the question, do you rebut what I say, or do you, in fact, do that part of the systems design? CRANE: This is certainly an important contribution to an integrated analysis--the knowledge gained by professional salvers and accident investigations. While it is included in a tacit way, I believe the rigorous kinds of analysis you mention would yield information in explicit ways that would lead to improved design and practices.