Section 3 Loads and factors

3.1.1 This Section describes and defines the loads considered necessary and relevant to be applied to an OPTS as a minimum.

3.1.2 Loads which are a result of the OPTS being used as a conventional offshore crane (e.g. ST-C with a SWL_CG and/or ST-M with a SWL_M) are to be taken from Ch 4, 3 Offshore cranes of the Code for Lifting Appliances in a Marine Environment, July 2022. The requirements given in Ch 4, 6 Handling of personnel and Ch 9, 4 Machinery engaged in handling of personnel of the Code for Lifting Appliances in a Marine Environment, July 2022 for an offshore crane engaged in the handling of personnel are also to be complied with.

3.1.3 Loads which are a result of any operation modes or designs of the individual OPTS which might not be detailed in this Section shall also be considered. Such additional loads are required to be agreed with LR prior to commencing of the project.

3.1.4 The typical loads and environmental parameters acting on an OPTS are shown in Figure 1.3.1 Examples of principal loads acting on an OPTS, which shows a typical ST-H OPTS.

Figure 1.3.1 Examples of principal loads acting on an OPTS

3.1.5 The following in-service and out-of-service modes are to be considered for an OPTS, as a minimum:

1. stowage (out-of-service);
2. pre-operation phase (in-service);
3. normal operation (in-service);
4. post-operation phase (in-service);
5. emergency and failure modes; and
6. other modes depending on the special design of the OPTS, e.g. in-field transit.

The various modes are further described in the following paragraphs Ch 1, 3.1 General 3.1.6 to Ch 1, 3.1 General 3.1.11.

3.1.6 During stowage the system is to be subjected to the following loads, as a minimum:

1. dead loads;
2. loads due to static and dynamic stowage specific mothership inclinations acting on the OPTS;
3. inertia loads due to stowage specific mothership motions (i.e. vertical and horizontal accelerations) acting on the OPTS;
4. stowage specific securing or restraining forces applied by means of system internal or external lashing devices;
5. wind and other environmental effects (e.g. green sea); and
6. snow and ice.

3.1.7 In the pre-operation phase the OPTS is usually released from its stowage arrangements. The following loads shall be considered in the pre-operation phase as a minimum:

1. dead loads;
2. personnel related SWL_P and/or UDL_P acting on structure, as applicable;
3. cargo related SWL_CG, as applicable;
4. loads due to static and dynamic mothership inclinations affecting the OPTS and its SWL_P and/or UDL_P acting on structure, as applicable;
5. loads due to static and dynamic mothership inclinations affecting the SWL_CG, as applicable;
6. wind forces and environmental effects (e.g. green sea);
7. loads in operational phases where the motion compensation is inactive or non-existent:
   1. Inertia loads due to mothership motions (e.g. vertical and horizontal accelerations) applied to the SWL_P, and/or UDL_P acting on structure, as applicable;
   2. Inertia loads due to mothership motions (e.g. vertical and horizontal accelerations) applied to the OPTS and acting on all components of the OPTS structure, as applicable; and
   3. Inertia loads due to mothership accelerations (vertical and horizontal) affecting the SWL_CG;
8. loads in operational phases where the motion compensation is active;
9. Inertia forces due to accelerations caused by the compensation system (e.g. due to uncompensated motion or residual accelerations caused by not fully effective motion compensation) acting on all SWL, UDL and OPTS structure;
10. forces due to OPTS movements, such as slewing, telescoping and luffing;
11. snow and ice when considered relevant; and
12. internal loads in the various components of the system, e.g. wire rope line pull for telescoping.

3.1.8 During normal offshore personnel transfer operations, the system shall be subjected to the following loads which are to be considered as a minimum:

1. Dead loads;
2. personnel SWL_P and/or UDL_P;
3. cargo SWL_CG as applicable;
4. loads due to static and dynamic mothership inclinations acting on the OPTS and its SWL_P, UDL_P and SWL_CG;
5. wind forces and environmental effects;
6. inertia loads due to mothership accelerations (vertical and horizontal) acting on the ST-P system type OPTS and its SWL_P, UDL_P and SWL_CG;
7. inertia forces due to accelerations caused by the compensation system (e.g. due to residual accelerations caused by not fully effective motion compensation) for ST-A and ST-H system type OPTS;
8. forces due to OPTS movements, such as slewing, telescoping and luffing;
9. defined contact loads, e.g. from the gangway tip pushing with a defined pre-load against the target structure as specified by the designer/manufacturer;
10. snow and ice when considered relevant; and
11. internal loads in the various components of the system, e.g. wire rope line pull for telescoping.

3.1.9 Environmental conditions which result in green sea or any other wave loads hitting the gangway are not expected to occur during normal operation of the OPTS.

3.1.10 The post-operation phase is considered similar to the pre-operation phase in reverse order. In case the post-operation phase has special operational characteristics, any resulting loads which are not given in Ch 1, 3.1 General 3.1.7 shall be taken into consideration. Personnel on the gangway or in the personnel containment are not expected during pre- or post-operation.

3.1.11 Other in-service or out-of-service modes may need to be considered depending on the individual design and/or environmental and/or local conditions of the OPTS.

3.1.12 The design analysis of the OPTS shall cover all geometric configurations and associated loading conditions.

3.1.13 All loads for the OPTS shall be associated with the mothership specific accelerations which are to be based on the location of the OPTS on the mothership and the significant wave heights. In case the mothership is not defined, a design envelope shall be defined which includes all loads which are relevant for the design of the OPTS. For each individual project it is to be ensured that this design envelope is not exceeded.

3.1.14 Where components (e.g. winches, hydraulic cylinders) are designed for a specific design envelope (i.e. minimum and maximum, as applicable, nominal static and dynamic interface loads), it is to be ensured that such design envelope loads are always equal or above the OPTS specific design interface loads.

3.1.15 The design life time for the OPTS shall be defined by the Owner/Operator but shall be taken as a minimum of 20 years. Appropriate fatigue calculations in accordance with a recognised National and International Standard shall be carried out for critical welds, parts and components in order to ensure that the desired life time will be reached. In special cases longer or shorter design life times may be agreed between the Owner/Operator, designer/manufacturer and LR.

3.1.16 Unless specified otherwise by the manufacturer, the design life of components which are subject to wear may be taken as 5 years and regular maintenance is to be ensured. The maintenance procedures need to ensure that components are replaced before a critical state is reached.

3.1.17 The co-ordinate system for the OPTS may be defined as follows:

1. Origin: The origin may be taken at the location of the heel pin of the OPTS or a similar location depending on the individual design.
2. X-axis: May be taken towards the longitudinal direction of the gangway or personnel containment where the positive direction is defined as ‘from gangway heel to gangway tip’.
3. Y-axis: May be taken as the transverse direction of the gangway or personnel containment.
4. Z-axis: May be taken as the vertical direction of the gangway or personnel containment where the positive direction is defined as ‘upwards’.

For an example of a co-ordinate system, see Figure 1.3.1 Examples of principal loads acting on an OPTS.

3.2.1 The dead load of all structure, components, parts and arrangements is to be considered as its nominal weight. The nominal weight may be the conservatively calculated (i.e. use of negative plate thickness tolerances) or measured weight.

3.2.2 The dead load of travelling cargo trolleys is to be considered as part of the live load, i.e. SWL_CG.

3.2.3 The dead load of fixed cargo baskets is to be considered as part of the dead load.

3.2.4 The dead load is to be enhanced by the applicable risk coefficient as defined in Ch 1, 3.8 Risk coefficient in all load cases related to the lifting and transfer of persons.

3.3.1 For OPTS where the access is restricted (A-GR) the SWL_P,n shall be applied. In case the OPTS is also used for cargo handling on the gangway the SWL_CG is to be considered in addition.

3.3.2 The Safe Working Load, SWL_P,n is to be taken as:

If equipment heavier than 10 kg needs to be carried by the personnel, the value for W_P shall be adjusted to account for the higher weight. The limits according to labour law for persons carrying weight without supporting aids need to be complied with.

An emergency load of SWL_P.emergency =360 kg shall be applied at the most unfavourable location on the gangway or personnel containment. This is considered to be equivalent to a minimum of two persons and a person on a stretcher. If the personnel containment is large enough to accommodate two persons and a person on a stretcher, this load shall be taken into account for a personnel containment type OPTS. Alternatively, the personnel containment specific emergency load SWL_P.emergency shall be applied if this load is beyond 360 kg.

3.3.3 All SWL_P and SWL_CG loads shall be applied at unfavourable positions (e.g. causing maximum bending moments) and assuming unfavourable support conditions (e.g. cantilever position, supported at both ends, etc.) which may occur during in-service conditions.

3.3.4 If the OPTS is foreseen to be used in cases of emergency evacuation, the below defined UDL_P shall be applied as a design load and not the SWL_P.

3.3.5 Where the OPTS is also used as a conventional offshore crane with or without handling of personnel, the SWL_C and SWL_M are to be defined.

3.3.6 The above Safe Working Loads SWL_P, SWL_P.n, SWL_P.emergency and SWL_M are to be enhanced by the applicable risk coefficient as defined in Ch 1, 3.8 Risk coefficient.

3.4.1 For OPTS where the access is unrestricted (A-GU) an UDL_P shall be applied.

3.4.2 The uniformly distributed load, UDL_P, is to be taken as:

UDL_P =360 kg/m²

The above defined UDL_P shall also be applied to waiting zones before entering the actual gangway in case of A-GU type designs. Consideration may be given to technically justified proposals to apply lower UDL_P figures.

3.4.3 The UDL_P shall be partly applied to the gangway structure where this will lead to a higher utilisation of the OPTS assuming the most unfavourable support conditions (e.g. cantilever position, supported at both ends, etc.) possible.

3.4.4 The above uniformly distributed load, UDL_P, is to be enhanced by the applicable risk coefficient as defined in Ch 1, 3.8 Risk coefficient

3.4.5 This above defined Uniformly Distributed Load, UDL_P shall be further increased by the mothership accelerations and loads from any compensated or uncompensated (residual) motions of the OPTS. The inclinations of the mothership shall also be taken into consideration.

3.5.1  Floorings are to be designed for the following loads and do not need to be applied simultaneously:

1. Case A: Distributed load of 360 kg/m²; and
2. Case B: Local load of 310 kg on any individual member.

3.5.2 For both cases, the mothership accelerations and loads from any compensated or uncompensated (residual) motions of the OPTS shall be applied. These loads are to be further enhanced by the applicable risk coefficient as defined in Ch 1, 3.8 Risk coefficient. The allowable stresses shall be calculated as per Ch 1, 5 Allowable stresses and safety factors using the stress factor as defined in Table 1.4.2 Stress factors for the defined load cases for Case 1.

3.6.1 The distributed load on platforms and walkways shall be a minimum of 360 kg/m² and a concentrated load of 310 kg at the most unfavourable location on the platform or walkway. These loads do not need to be applied simultaneously. These loads shall be increased by the mothership accelerations and loads from any compensated or uncompensated (residual) motions of the OPTS. The inclinations of the mothership shall also be taken into consideration. These loads are to be further enhanced by the applicable risk coefficient as defined in Ch 1, 3.8 Risk coefficient.

3.6.2 The distributed load shall be applied to the platform or walkway structure in such a way that leads to the highest utilisation of the OPTS or platform or walkway structure. This could mean that the distributed load may only be partly applied to the OPTS or walkway or platform area.

3.7.1 Handrails and their supporting structure (e.g. guard rails and stanchions) shall be designed to a minimum distributed load of 51 kg/m without permanent deformation. This distributed load may be increased by the mothership accelerations and loads from motions of the OPTS. The inclinations of the mothership shall also be taken into consideration. This load is further to be enhanced by the applicable risk coefficient as defined in Ch 1, 3.8 Risk coefficient

3.8.2 The above defined risk coefficients shall be used to enhance the values of the SWL, UDL and dead load and are to be applied for allowable stress design (ASD) and load and resistance factor design (LRFD).

3.8.3 The risk coefficients shall be applied to all operational and non-operational loads, including emergency loading conditions, where lifting, supporting and transfer of personnel is carried out.

3.8.4 Proposals for the application of alternative risk factors will be specially considered if supported by an acceptable technical justification.

3.9.1 The application of a hoisting factor for the personnel transfer function of the OPTS is not required. If the OPTS is also designed to be used as a conventional offshore crane, a hoisting factor is required to be applied (see Ch 4, 3.3 Dynamic forces of the Code for Lifting Appliances in a Marine Environment, July 2022). This is also to be applied for systems where the crane part of the system is engaged in the handling of personnel (i.e. lifting of personnel in a suspended basket). Reference is made to Ch 1, 3.1 General 3.1.2.

3.10.1 The application of a duty factor for the personnel transfer function of the OPTS is not required. If the OPTS is also designed to be used as a conventional offshore crane, a duty factor is required to be applied (see Ch 4, 3.2 Service category and duty factor of the Code for Lifting Appliances in a Marine Environment, July 2022) to the purpose of serving as an offshore crane. This is also to be applied for systems where the crane part of the system is engaged in the handling of personnel (i.e. handling of personnel in a suspended basket). Reference is made to Ch 1, 3.1 General 3.1.2.

3.11.1 Inertia forces acting on the OPTS due to mothership motions shall be specified by the Owner/Operator for all in-service and out-of-service (e.g. stowed for voyage or in-field transit) situations. The translational and angular accelerations resulting from the mothership motions shall be defined for each of the given in-service or out-of-service significant wave heights and shall also be associated with the location on the mothership.

3.11.2 If the actual mothership is unknown, and consequently actual accelerations are not available, the OPTS shall be designed for a given set of maximum accelerations which shall contribute to the design load envelope.

3.11.3 The residual accelerations as a result of uncompensated mothership motions are to be considered. The residual component accelerations shall be taken as at least 15 per cent of the maximum uncompensated component accelerations for the applicable operational load case and associated significant wave height. If the motion compensation system cannot achieve less than 15 per cent of the maximum uncompensated component accelerations the actual residual accelerations are to be applied in the design calculations. Lower residual accelerations than the minimum of 15 per cent may be applied if it can be demonstrated that those can be reliably achieved by the system.

3.11.4 Where sinusoidal motions are used to establish design accelerations, the maximum and residual acceleration calculations should be made for a range of likely motion periods. Where random motions are used to establish design accelerations, the maximum acceleration a_max shall be taken as 3,72 times the RMS acceleration, i.e.:

If time domain simulation is used, the RMS accelerations shall be established over at least 10 minutes full scale simulation time.

3.11.6 The vertical and horizontal location of the OPTS and its components shall be taken into consideration for the application of accelerations, e.g. an OPTS installed at the stern or bow of the mothership usually results in higher accelerations than an OPTS installed at midships of the mothership. An OPTS located close to the port side or starboard side of the mothership will also experience higher accelerations than an OPTS installed close to the centreline of the mothership.

3.11.7 Any movement of the target unit shall also be taken into consideration where the gangway or personnel containment may come in contact with the target structure. Combined accelerations of the mothership and the target unit need to be considered as applicable (e.g. when the gangway is resting on the target structure in passive mode). Representative values for the target unit accelerations shall be agreed with LR.

3.11.8 The performance of mothership stabilisation systems such as anti-roll tanks or Dynamic Positioning may be included when defining the mothership motions and accelerations.

3.12.1 The static inclinations of the mothership shall be considered for the OPTS.

3.12.2 Static inclinations shall be provided by the Owner/Operator of the mothership. In the absence of such information the values in Table 1.3.1 Static inclination angles for different unit types may be applied.

3.12.3 As an OPTS is usually capable of slewing around its centreline at the base structure, load cases shall be considered where the heel and trim angles of the mothership are combined in a resulting angle δ as per the following equation:

3.12.4 The minimum possible combinations are given in Table 1.3.2 Minimum possible combinations of load angles. In this table pairs of load angles are provided which can be used for the analysis of the OPTS.

3.12.5 The rolling and pitching motions alternate around static heel and trim angles. The effects of the final maximum static angles of roll and pitch, which include static heel and trim angles, shall also be taken into consideration.

3.12.6  The load reducing effects of an installed motion compensation system may be considered. Components of the OPTS which are affected by the load reduction shall be subjected to a minimum of 15 per cent of the static inclination angles due to residual inclinations which may not be compensated by the system at all times. Lower inclinations than the minimum of 15 per cent may be applied if it can be demonstrated that those can be reliably achieved by the system.

3.13.1 Dynamic forces due to travelling, slewing, telescoping and luffing motions are to be taken into consideration as applicable to the individual design. Centrifugal forces due to slewing are also required to be taken into consideration as they may be significant in active motion compensated systems. Any proposal to omit centrifugal forces will be specially considered.

3.13.2 The actual speed and acceleration and deceleration times shall be used to determine the inertia forces.

3.14.1 The forces due to wind shall be applied to the system and components directly exposed to wind action. Wind action on shielded surfaces shall also be appropriately considered. See Ch 4, 2.12 Wind loading of the Code for Lifting Appliances in a Marine Environment, July 2022.

3.14.3 The design wind speeds as defined in Ch 1, 3.14 Wind 3.14.2 are related to a gust wind velocity averaged over a period of 3 seconds.

3.14.4 The application of higher in-service design wind speeds needs to be considered to match the design environmental conditions (e.g. significant wave height). See Ch 1, 2.3 Service category 2.3.2 of the Code for Lifting Appliances in a Marine Environment, July 2022.

3.14.5 The actual operational wind speeds for personnel transfer operations shall be less than the above design wind speeds (see Ch 2, 3.5 Environmental aspects 3.5.1).

3.14.6 Methods to evaluate loads due to wind action are given in Ch 4, 2.12 Wind loading of the Code for Lifting Appliances in a Marine Environment, July 2022. Alternative proposals to determine loads due to wind in compliance with recognised National or International Standards will be specially considered.

3.15.1 The loads due to stowage acting on the OPTS and its components are in general to be taken into account as per the requirements as stated in Ch 4, 2.11 Forces due to ship motion of the Code for Lifting Appliances in a Marine Environment, July 2022.

3.15.2 The stowage loads may be calculated based on the design conditions as given in Ch 4, 2.11 Forces due to ship motion 2.11.3 of the Code for Lifting Appliances in a Marine Environment, July 2022.

3.15.3 Where the mothership characteristics are known, the method given in Ch 4, 2.11 Forces due to ship motion 2.11.4, Ch 4, 2.11 Forces due to ship motion 2.11.5 and Ch 4, 2.11 Forces due to ship motion 2.11.6 of the Code for Lifting Appliances in a Marine Environment, July 2022 shall be applied.

3.15.4 Stowage loads based on model tests or hydrodynamic calculations of the mothership may also be applied instead of Ch 1, 3.15 Stowage 3.15.2.

3.15.5 Snow and ice loads are to be considered as defined in Ch 1, 3.17 Snow and ice.

3.15.6 The effects of green sea need to be taken into consideration in cases where the stowage arrangements and location on the mothership may result in significant green sea loads.

3.15.7 Actual stowage load data as per Ch 1, 3.15 Stowage 3.15.3 or Ch 1, 3.15 Stowage 3.15.4 is to be preferred over the general method as given in Ch 1, 3.15 Stowage 3.15.2. Due care is to be taken in cases where the OPTS is not permanently installed on a dedicated mothership. In such cases, it is to be ensured that the design stowage loads are always greater than the stowage loads of the actual mothership on which the movable OPTS is installed.

3.15.8 Alternative proposals to calculate the stowage loads for the OPTS will be specially considered.

3.15.9 In case in-field transit is considered in the OPTS concept, lower loads corresponding to the in-field-transit mode may be accepted.

3.15.10 For a definition of the different stowage cases, general transit/voyage (stowage/survival) and in-field transit, see Ch 1, 4.3 General transit/voyage (stowage/survival) and in-field transit load combinations.

3.16.1 The risk assessment shall identify and define possible emergency scenarios and hazards.

3.16.2 Based on the results of the risk assessment (see Ch 1, 10 Risk assessment) possible emergency loads are to be developed and defined. Any relevant loading scenarios as a result of the risk assessment shall be included in the design load cases for the OPTS.

3.16.3 Examples for such scenarios are given, but shall not be limited to the following:

1. Single point failure of any single component resulting in emergency loads beyond those of normal operation or stowage.
2. Partial failure of the motion compensation system (e.g. resulting in increased mothership accelerations).
3. Complete failure of the motion compensation system (e.g. resulting in uncompensated mothership accelerations).
4. Control system failure causing the failure of any type of motion compensation system or other parts of the OPTS.
5. Failure of certain system components (e.g. resulting in increased or uncompensated mothership accelerations).
6. Burst of a hydraulic hose causing the pilot operated non-return valve of the hydraulic cylinder to lock the cylinder rod.
7. Exceeding of geometrical design limits, e.g. steel to steel contact of hydraulic cylinder parts.
8. Falling below the minimum specified ambient operating temperature, combined with the occurrence of impact forces.
9. Impact loads at the gangway tip or the personnel containment due to inaccurate or inadequate operation or failure of components or systems. The applied impact load shall be at least 25 per cent above the set level of any load limit sensors, e.g. contact pre-load of the telescopic gangway system, slewing motor load limit setting, etc.
10. Emergency disconnection (lift-off), e.g. due to exceeding of design envelope (e.g. exceeding of design loads or geometrical design limits, etc.).
11. Emergency stop.
12. Accidental wave loads or green seas acting on the gangway and/or OPTS structure during stowage and normal operation.
13. Consideration of the 'double angle effect', where the OPTS motion compensation system might have stopped operating due to a failure or due to an emergency stop activation in an unfavourable moment resulting in potentially twice the design mothership inclination the OPTS has been designed for.
14. Exceeding of geometrical limitations of the OPTS.
15. Rescue of a person on a stretcher.
16. Other aspects depending on the design of the OPTS and the risk assessment may need to be considered.

3.16.4 The above described emergency scenarios and other similar events are to be categorised as load case 4 events as defined in Ch 4, 2.15 Load combinations of the Code for Lifting Appliances in a Marine Environment, July 2022.

3.16.5 For ST-A and ST-H system types OPTS, the design analysis in an emergency case of compensation system failure shall cover all the loads specified in Ch 1, 3.1 General 3.1.8, however, the inertia loads due to the mothership accelerations acting on the OPTS dead load and its SWL_P, UDL_P and SWL_CG shall be taken as full accelerations without compensation.

3.16.6 If the OPTS has experienced any of the above emergency scenarios and/or loads, the OPTS is to be taken out of service and shall be thoroughly examined before being put back into use.

3.17.1 In general, the effects of snow and ice loads acting on the OPTS structure do not need to be considered, except where a particular design or application indicates that these loads are significant.

3.17.2 If the risk assessment results in the conclusion that in certain areas of the system the presence of ice will not cause any hazards for personnel (e.g. due to dropped objects) and equipment, ice may be allowed in such areas. In such cases the load increasing effects of ice need to be considered.

3.17.3 The effects of snow and ice shall be considered for the calculation of the area exposed to wind in the stowage load case.

3.17.4 For the stowage load case the loads from snow and ice shall be taken as 400 kg/m³ for snow and as 900 kg/m³ for ice. The minimum thickness to be considered shall be 100 mm. Alternative proposals for consideration of snow and ice loads will be specially considered.

3.17.5 The risk (and its mitigation) of ice dropping from the system and its components with the potential to result in injured personnel needs to be considered in the risk assessment.

3.18.1 The effects of temperature shall be considered predominantly with respect to the selection of steel. Reference is made to Ch 4, 2.14 Temperature effects 2.14.1 of the Code for Lifting Appliances in a Marine Environment, July 2022.

3.18.2 Loads resulting from the effects of restraint due to thermal expansion/contraction shall be considered as applicable.

3.18.3 Hazards originating from temperature effects shall be taken into consideration. Reference is made to Ch 1, 10 Risk assessment.

3.19.1 Components may be designed for their own independent design loads in order to enable independent certification of such components. It must be ensured that the chosen design loads are in all cases compatible with the dynamic loads originating from the actual OPTS design load at the interface with the component. Any dynamic effects (such as mothership accelerations), risk coefficients and other design factors and loads are to be taken into account when comparing OPTS design interface load with the component design load.

3.19.2 The following components have the potential to be considered for their own design loads, e.g.:

1. winches;
2. hydraulic cylinders;
3. electro-mechanical actuators;
4. items of loose gear;
5. slewing rings; and
6. wire rope sheaves.

Other components will be specially considered.

3.20.1 System internal forces, such as resistance forces due to friction of sliding and guiding surfaces between the telescoping and non-telescopic parts of the gangway shall be taken into consideration. The friction coefficients are usually subjected to variation, e.g. depending on condition of the lubrication system, etc. Therefore, the minimum and maximum values of the friction coefficients shall be considered.

3.20.2 Forces due to inertia, such as acceleration and deceleration forces of the telescopic part of the gangway in the longitudinal direction of the gangway shall also be taken into consideration.

3.20.3 In order to ensure safe operation, it is usually required that direct contact between the gangway tip (or the personnel containment structure) and the target structure is established. The forces due to that direct contact need to be considered in the system design. The longitudinal contact load shall be based on the residual inaccuracy of the motion compensation system and the maximum pushing force the system can apply (e.g. due to telescoping action). The transverse contact force shall be based on the residual inaccuracy of the motion compensation system and the maximum slewing moment the system can apply. Alternative proposals for the application of such contact forces will be considered.

3.21.1 Contact loads are defined as loads which occur due to the gangway tip or personnel containment coming into contact with the target unit via the target structure.

3.21.2 Loads due to set pre-loads (e.g. due to predefined contact load from the telescopic system of the gangway) are to be taken into consideration as operational loads.

3.21.3 Loads due to uncompensated (residual) motion are to be taken into account.

3.21.4 The whole OPTS structure, and particularly the structure at the gangway tip or personnel containment, is to be designed to resist such contact forces combined with all other normal operation loads or emergency loads respectively.

3.22.1 Where the OPTS is intended to be used and is designed for special operational or environmental scenarios which will result in loads in excess of or in addition to those given in this Section, these loads are required to be taken into consideration. An example of such a scenario is the use of the OPTS gangway as a support for items other than personnel or cargo, e.g. fire hoses.

3.22.2 Loads due to wind induced vibrations (commonly known as vortex shedding) may need to be taken into consideration. The effects of vortex shedding, in particular, where the exciting frequency is near or matching the eigenfrequency is further to be taken into consideration. Any effects of possible fatigue damage may need to be assessed.

3.22.3 Other special loads may need to be considered and may be the result of the risk assessment.

3.22.4 All scenarios resulting in special loads are required to be described in detail and shall be agreed with LR.