CROW-CUR Richtlijn 7:2024 Flexible Dolphins

Deze tekst is gepubliceerd op 11-07-24

Definition of design situations and combinations

The relevant design situations (DS) must be selected taking into account the circumstances under which the structure must fulfil its function. Ultimate limit state design situations are classified as follows:

Persistent design situations, which refer to the conditions of normal use;
Transient design situations, which refer to temporary conditions applicable to the structure, e.g., during execution or repair;
Accidental design situations, which refer to exceptional conditions that may apply to the structure, e.g., to fire, explosion, collision, impact or the consequences of localised failure.

For a flexible dolphin structure, the following design situations (DS) and load combinations (LC) may be considered (depending on its function), also refer to Table 6-18 below:

ULS GEO/STR - Persistent Design Situation

Breasting/Mooring Dolphin: Ship in berth

-	(LC a) Design berthing scenario ( $F_{E, d}$ ) with operational wind, waves and current [based on (limiting) operational environmental conditions for ship] + live loads

-	(LC b) Design mooring scenario ( $F_{M d}$ ) with operational wind, waves and current [based on (limiting) operational environmental conditions for ship] + live loads

Breasting/Mooring Dolphin: No ship in berth

-	(LC c) Design wind, wave and current conditions [50 to 100-year return period environmental conditions] + live loads

Lead-in dolphins in front of lock or bridge foundation

-	(LC a) Design ship impact scenario ( $F_{E, d}$ , typically angular) + live loads

-	(LC c) Design wind, wave and current conditions [50 to 100-year return period environmental conditions] + live loads

Topside support dolphin (e.g. leading light)

-	(LC c) Design wind, wave and current conditions [50 to 100-year return period environmental conditions] + live loads, including effect of topside

ULS GEO/STR - Transient Design Situation

ULS GEO/STR - Accidental Design Situation

Breasting Dolphin (

F_{E, α}

)

-	(LC d) Uncontrolled ship berthing approach impact on dolphin

Crash Barrier/Lead-in dolphin/Topside support dolphin (

F_{E, α}

)

-	(LC d) Uncontrolled ship manoeuvre leading to impact on a (crash) barrier protecting a sensitive structure, a lead-in dolphin or supporting dolphin

Mooring Dolphin (

F_{M, α}

)

-	(LC e) Bollard misuse [too many lines around bollard]

-	(LC e) Equipment failure on ship with 1.18 x MBL

-	(LC e) Ship in berth in combination with survival / very extreme weather conditions [50 to 100-year return period environmental conditions]

SLS - Characteristic Design Situation

Breasting/Mooring Dolphin: Ship in berth

-	(LC f) Characteristic berthing scenario ( $F_{E, c}$ ) with operational wind, waves and current [based on (limiting) operational environmental conditions for ship] + live loads

-	(LC g) Characteristic mooring scenario ( $F_{M c}$ ) with operational wind, waves and current [based on (limiting) operational environmental conditions for ship] + live loads

Breasting/Mooring Dolphin: No ship in berth

-	(LC h) Characteristic wind, wave and current conditions [50 to 100-year return period environmental conditions] + live loads

Lead-in dolphins in front of lock or bridge foundation

-	(LC f) Characteristic ship impact scenario ( $F_{E, c}$ , typically angular) with operational wind, waves and current + live loads

-	(LC h) Characteristic wind, wave and current conditions [50 to 100-year return period environmental conditions] + live loads

Topside support dolphin (e.g. leading light)

-	(LC h) Characteristic wind, wave and current conditions + live loads, including the effect of topside

Table 6-18 Breasting/Lead-in Dolphin/Crash barriers – Load Combinations

Scenario	Berthing			Mooring			No ship
Limit state (LS) Design situation (DS)	SLS Char. DS	ULS Per. DS	ULS Acc. DS	SLS Char. DS	ULS Per. DS	ULS Acc. DS	SLS Char. DS	ULS Per. DS
Load combination (LC)	(LC f)	(LC a)	(LC d)	(LC g)	(LC b)	(LC e)	(LC h)	(LC c)
Loads:
Berthing characteristic	$F_{E, c}$	-	-	-	-	-	-	-
Berthing design	-	$F_{E, d}$	-	-	-	-	-	-
Berthing accidental	-	-	$F_{E, α}$	-	-	-	-	-
Mooring characteristic	-	-	-	$F_{M c}$	-	-	-	-
Mooring design	-	-	-	-	$F_{M d}$	-	-	-
Mooring accidental	-	-	-	-	-	$F_{M α}$	-	-
Operational wave, wind, current 1)	1.0	γ Q	-	1.0	γ Q	-	-	-
50 to 100 year RP wave, wind, current 2)	-	-	-	-	-	-	1.0	γ Q
Live load 1)	1.0	γ Q	-	1.0	γ Q	-	1.0	γ Q

Note:

¹⁾ These loads only need to be applied when having an unfavourable effect on the internal forces of the dolphin pile

²⁾ The return period needs to be equal or higher than the design life of the structure and has a minimum of 50 years

These design situations and load combinations should be performed in combination with the following design input variables:

Soil properties (upper and lower bound consideration of soil parameters)
Impact level (due to multiple fenders, tidal variations, vessel loading conditions, ship range)
Seabed level (due to scour, sedimentation, bottom protection, maintenance dredging)
Fender (based on supplier manuals upper and lower bound fender properties considered)

Note: It is recommended to apply the corrosion allowance for the pile strength verification in combination with all other variables.

Multiple combinations of design input variables are possible. This means that , for example, a check for “pile strength” of a dolphin without fender should be performed for:

2 soil properties	(design upper & design lower)
2 berthing impact levels	(high & low)
2 seabed levels	(high & low)
		X
8 design input possibilities

Engineering judgement may be applied to reduce the number of variable combinations. However, this should be done with care as it is difficult to predict which combination of variables will be governing for pile design.

Table 6-19 Breasting/Lead-in Dolphin/Crash barriers - Limits States (LS), Design Situations (DS), Load combinations (LC), Design Checks and Variables

Limit State	Design Situation (DS) / Load Combination (LC)	Design Check	Design variable possibilities 5)
Limit State	Design Situation (DS) / Load Combination (LC)	Design Check	Soil	Impact	Seabed	Fender
Common limit states/design situations:
ULS – STR	Persistent Design Situation: (LC a) Design berthing ( $F_{E, d}$ ) (LC c) Design wind, wave and currents	Pile strength	Design upper Design lower 3)	High Low	High Low	Upper Lower
ULS – GEO		Hor. Pile stability (100% mob) Vert. pile stability Pile displacement	Design lower	High Low	Low	Lower
SLS	Characteristic Design Situation: (LC f) Characteristic berthing ( $F_{E, c}$ ) (LC h) Char. wind, wave and currents	Pile displacement Deformation at pile toe (fixity) 1)	Char. lower	High Low	Low	Lower
Limit states/design situations for specific conditions:
ULS – STR/GEO	Accidental Design Situation: (LC d) Uncontrolled ship impact ( $F_{E, α}$ )	Pile strength	Design upper Design lower 3,4)	High Low	High Low	Upper Lower
ULS – STR/GEO		Hor. pile stability (100% mob) Vert. pile stability Pile displacement Deformation at pile toe (fixity) 2)	Design lower 3,4)	High Low	Low	Lower
ULS – FAT	Mooring (cyclic lean-on) Wind, wave and currents (cyclic)	Pile strength	Char. upper Char. lower	High Low	High Low	Upper Lower

Table 6-20 Mooring Dolphin - Limits States (LS), Design Situations (DS), Load combinations (LC), Design Checks and Variables

Limit State	Design Situation (DS) / Load Combination (LC)	Design Check	Design variable possibilities 5)
Limit State	Design Situation (DS) / Load Combination (LC)	Design Check	Soil	Impact	Seabed
Common limit states/design situations:
ULS – STR/GEO	Persistent Design Situation: (LC b) Design mooring ( $F_{M, d}$ ) (LC c) Design wind, wave and currents	Pile strength Pile displacement Hor. pile stability (100% mob) Vert. pile stability	Design lower	High	Low
ULS – STR/GEO	Accidental Design Situation: (LC e) Accidental mooring ( $F_{M, α}$ )	Pile strength Hor. pile stability (100% mob) Vert. pile stability Pile displacement	Design lower 4)	High	Low
SLS	Characteristic Design Situation: (LC g) Characteristic mooring ( $F_{M, c}$ ) (LC h) Char. wind, wave and currents	Pile top displacement Deformation at pile toe (fixity) 1)	Char. lower	High	Low
Limit states/design situations for specific conditions:
ULS – FAT	Mooring (cyclic mooring line) Wind, wave and currents (cyclic)	Pile strength	Char. upper Char. lower	High Low	High Low

Notes:

¹⁾ This check verifies that plastic soil deformation at the pile toe does not contribute to energy absorption and/or results in permanent and/or progressive pile inclination under operational loading conditions.

²⁾ This check forces structural failure before geotechnical failure in case of accidental berthing impact scenarios in order to gain energy absorption capacity from major plastic deformations in the steel pile.

³⁾ Contrary to many other civil structures, for energy absorbing flexible dolphins, a partial safety factor of 1.0 on soil parameters typically results in the most onerous internal forces in the pile.

⁴⁾ Reduced partial safety factors on soil parameters apply (e.g. 1.0) for accidental loading scenarios.

⁵⁾ Possibilities means that soil (2 variables) + impact (2 variables) + seabed (2 variables) is 2 x 2 x 2 = 8 possibilities.

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Definition of design situations and combinations