RO-RO SAFETY
SUBDIVISION AND STABILITY PROGRAMME FINAL REPORT
R O / R O SAFETY
SUBDIVISION AND STABILITY RESEARCH PROGRAMME
T A S K 4 - CO-ORDINATION OF RESEARCH PROGRAMME AND EVALUATION
OF SURVIVAL STANDARDS
RESEARCH PROGRAMME AND EVALUATION OF SURVIVAL STANDARDS
4. INTRODUCTION
This specification describes a programme of work designed to follow on from the RoRo Safety Research Programme as laid down in the General Council of British Shipping's proposal to the Department of Transport, dated May 1987. The initial phase of research programme was broken down into three basic tasks :
Task 1 Ship Geometry
Task 2 Probability Calculation
Task 3 Casualty Analysis and Relative Safety
The contractor is to review the results of the work carried out under Tasks 1, 2 and 3 and where applicable to incorporate them in the Task 4 phase - Tanks Tests.
The contractor is to carry out a series of tank tests using a suitable huU form. The hull form is to be agreed with the Department of Transport and the General Council of British Shipping. The model layout is to be representative of the actual internal layout of Ro-Ro vessels.
The contractor is to incorporate the results of the tank tests and the analysis of such tank tests in proposals for a better definition of survival capability. The contractor is also to propose rules for the definition of the required subdivision under calculation.
4.1 TANK TEST PROGRAMME
4.1.1 Introduction
Tlie evaluation of survival capability after damage of both passenger and cargo ships is highly dependent upon the determination of the probabihty of "not capsizmg or sinking".
Attention is drawn to the observations made in Para 4 (a) "Criterial for capsizing and sinking" of the explanatory notes contained in the 1974 I M O probabihty based regulations. (IMO Resolution A265).
In particular these observations draw attention to the limited present state of knowledge. Designers and approving authorities can at present only rely upon the unique research carried out in the U K and the USA on two ship types about 20 years ago in assessing survival capability.
4.1.2 Objectives
The programme of tests described in this specification is intended to provide data which will be used, together with the results of tests carried out in the U K in the late 1960's to review, substantiate and where found necessary propose modifications to present criteria for capsizing and sinking.
It is also intended that the results should contribute to the framing of new national and intemational regulations.
Further tests are intended to assess the dynamic behaviour of the intact vessel with loose water on the vehicle deck, also to attempt to evaluate the value of reserve superstructure buoyancy in various configurations in resisting capsize.
Reference is made to the RINA paper read on 12 April 1973 entitled "Damage StabiHty Model Experiments", authors H Bird and R P Browne which describes the UK tests referred to above.
4.2 B A S I S S H I P
The department will supply the Contractor with details of a basis vessel which wih be intended to represent a typical twin screw Passenger Ro/Ro ferry of present day form and arrangements and about 120/150 metres length BP.
Information supplied will include :
Lines Plan and appendage details General Arrangement drawing Stability information.
4.3 MODEL
4.3.1 A model is to be constructed in GRP having a thickness of about 6mm, built to the moulded lines of the vessel and fitted with appendages.
The scale of the model is to about 1:25.
Below the bulkhead deck two transverse bulkheads are to be fitted amidships at such positions as will produce parallel sinkage to the margin line (76mm freeboard) from an intact condition corresponding to the subdivision waterline, when the space between the bulkheads is flooded. A soHd double bottom space is to be added in the compartment bounded by the transverse bulkheads.
This amidships compartment wiU be flooded in all tests carried out in the damaged condition and it is of vital importance that no extraneous water shall be allowed to enter in this or any other part of the models structure. Air entrainment during flooding is to be prevented by suitable air pipes.
To minimise scale problems the deck of the model above the midships compartment is to be of thin sheet metal construction.
Amidships damage is to be simulated by a removable trapezoidal watertight section in the model side. Length of the opening, which is to extend from double bottom to upper deck level, is to be .03L + 3.05 metres at subdivision waterhne with penetration into the bulkhead deck of 0.20 Breadth. The sides of the damaged
opening are to be sloped at 15 degrees.
The superstracture of the model is to be of GRP but with a perspex upper deck to allow visual sighting and video recording of movement of water on the bulkhead deck. The amidships damage is to be extended upwards to the requirements of the Department.
A centre casing of minimum dimensions and fitted well clear of the damaged opening may be arranged to house and give access to ballast weights.
End casing of sohd construction are to be fitted to represent those in the basis ship.
A l l spaces are to be fitted with efficient drainage arrangements.
4.3.2 A separate price is to be quoted for the constmction of the model together with supplementary prices for the following optional extra arrangements within the superstmcture all of similar constmction to the basic model.
i) Watertight transverse bulkheads at three positions in the length of the superstructure.
ü) Watertight longitudmal bulkheads each side of the model superstmcture at 0.2 Breadth from the sides over the full length of the model and fitted with subdividing transverse watertight bulkheads at three positions but on one side of the model only.
4.4 TEST PROGRAMME
4.4.1 The test programme is primarily intended to determine the minimum G M required to resist capsize in a variety of flooded freeboards and wave conditions.
Required survival G M is to be determined in the following conditions :
Flooded Freeboards of 0.076, 0.25, 0.50, 0.75 and 1.00 metres.
4.4.2 Contractors should base their quotation on a series of 40 systematic test conditions of freeboard and wave height in which G M is to be reduced by stages until capsize occurs. For each capsize condition the critical G M is to be determined within limits of + or - 0.05 metres (full scale). Contractors should allow a further 150 tests for this purpose. All tests are to commence in an upright condition. Tests are to be carried out with damage facing both "Leeward" and "Windward" sides.
4.4.3 Contractors should also indicate in their quotation their extra cost for any additional test runs that may be required.
4.4.4 Contractors should include in their quotation the cost of tests for each freeboard condition of determining the GM to resist capsize in still water (i.e. negative GM).
4.4.5 In addition to capsize tests in a flooded condition, the model is also to be tested in - waves of significant heights specified in para 4.4.1 and at a freeboard to be specified by the Department to evaluate dynamic behaviour in the intact condition, with varying quantities of water on the bulkhead deck (6 tests in each wave height).
4.4.6 Contractors should indicate in their quotation the extra costs of repeating the tests described in para 4.4.5 for the two alternative superstructure geometries described in para 4.2.2.
4.5 WAVE DEFINITION
Irregular uni-directional waves having significant heights specified in para 4.4.1 and conforming to the Derbyshire Coastal Water formulation modified as required by the Department are to be generated for the tests.
Tests are to be commenced with the model ahgned parallel to the wavemaker and at a distance sufficient to ensure formation of the required irregular wave pattem.
Each test is to be continued (unless capsizing occurs) for a minimum of 10 minutes. During tests the model is to be allowed to drift without restraint. Any test exceeding 10 minutes without capsize is to be regarded as meeting survival requirements.
4.5 CG VARIATION
Ballast weights are to be arranged to permit fine adjustment to GM to be achieved. Contractors proposals are to be submitted in outline with their tender.
4.7 The dry weight of the model is to be determined before commencement of tests and is to be checked at regular intervals. In the event that a check shows significant change in weight from original (greater than + 0.5%) then the Department may require all tests from the time of the last satisfactory check to be repeated, also that corrective measures be taken to prevent recurrence.
4.8 FREEBOARD CHECKS
Draught marks are to be arranged forward, aft and amidships on both sides of the model Before the commencement of each test the freeboard amidships is to be carefully checked.
4.9 INCLINING EXPERIMENTS
For all tests and for both flooded and intact conditions an inclining experiment is to be carried out in water to determine KG values.
Contractors are additionaUy required to determine GZ values for the model as tested. Methods by which this requirement will be met are to be described when tendering. Basis ship intact and damaged GZ particulars will be provided by the Department.
4.10 ROLL PERIOD
The Department will supply roll period infonnation for the basis vessel. RoU inertias are to be arranged to be as close as practicable to ship conditions.
4.11 VIDEO RECORDINGS
Video records are to be made of not less than 20 selected flooded tests also of 12 intact tests with water on deck.
4.12 REPORT
Contractors are to :
i) Tabulate all test results with annotations describing mechanisms of capsize, time of duration of test, etc.
ii) Describe in graphical form the characteristics of wave forms used in the tests.
iii) Produce hydrostatics, GZ values and cross cuives for the model in intact and flooded conditions.
iv) Produce curves showing the boundary between survival and capsize plotted on co-ordinates of flooded G M and significant height for each freeboard tested.
v) Prepare a full description of the model, test programme, procedures, etc. together with a discussion of the results obtained.
4.13 INTERPRETATION OF RESULTS
Contractors are invited to offer assistance in the analysis and interpretation of the results of this programme of tests. Curricula Vitae and fee proposals (based on daily rates) for appropriate experts should be appended separately to quotations.
4.14 ALTERNATIVE PROPOSALS
Contractors are invited to submit alternative proposals, separately priced, which they feel may be more effective in achieving the objectives outlined in para 4.1.
4.15 SUPERVISION
All tests and other work contained in this specification are to be carried out to the full satisfaction and approval of the Department's nominated Project Manager.
4.16 TIMING
Contractors are to include within their quotations a programme of tests in the form of a bar chart, indicating the earhest possible starting date.
In view of the urgency attached to the completion of the proposed work, Contractors are required to submit a reahstic and achievable programme.
4.17 DESCRIPTION OF FACILITIES
Contractors should include with their quotation a full description of the facilities they would propose to utüise in the test programme specified.
(REF:SAR29401.ROR)
