s trestle and loading platforms

:

S Trestle and loading platforms

Report number : Revision : Date : Date docume 24/06/08

Client

XXXX Badhuisweg 3 1031 CM Amsterdam

Author

Name: Direct line: E-mail:

© No part of this report [drawing] and/or design may be reproduced, published and/or passed to any third party, without the prior written consent of Delta Marine Consultants. Delta Marine Consultants is a tradename of BAM Infraconsult bv.

A DRAFT MMU 06-09-08 06-09-08 LGR

Revision Status Author Date Verified Date Released DMC Date

Structural Analysis Existing Trestle and loading platforms revision A 18 November 2008 2 / 72

Index

1 Introduction .............................................................................................. 5

2 3-D Modelling ........................................................................................... 6

2.1 TRESTLE ............................................................................................................ 6

2.1.1 Substructure ...................................................................................................................... 7

2.1.2 Superstructure .................................................................................................................. 9

2.1.3 Jacket @ Bent 35 ............................................................................................................ 10

2.2 LOADING PLATFORMS ................................................................................... 12

2.2.1 Substructure parking area platform A .......................................................................... 12

2.2.2 Substructure parking area platform B .......................................................................... 13

2.2.3 Substructure platforms .................................................................................................. 13

2.2.4 Superstructure ................................................................................................................ 16

3 Loads ...................................................................................................... 17

3.1 TRESTLE LOADS ............................................................................................. 17

3.1.1 Self weight construction ................................................................................................ 17

3.1.2 Deadweight concrete roadway ...................................................................................... 17

3.1.3 Dead load existing piping............................................................................................... 18

3.1.4 Dead load new piping ..................................................................................................... 19

3.1.5 Horizontal pipe load (Anchor forces) ............................................................................ 20

3.1.6 Horizontal pipe loads (Friction forces .......................................................................... 21

3.1.7 Vertical truckload ............................................................................................................ 22

3.1.8 Wind load east west ........................................................................................................ 22

3.1.9 Wind load north south .................................................................................................... 23

3.1.10 Live load ........................................................................................................................... 24

3.1.11 Wave forces extreme condition ..................................................................................... 25

3.1.12 Wave forces normal condition ....................................................................................... 26

3.1.13 Temperature load ............................................................................................................ 27

3.1.14 Seismic load .................................................................................................................... 28

3.1.15 Dead weight concrete collar on piles ............................................................................ 28

3.1.16 Vehicle loading ................................................................................................................ 29

3.2 LOADING PLATFORMS ................................................................................... 31

3.2.1 Self weight construction ................................................................................................ 31

3.2.2 Deadweight concrete roadway ...................................................................................... 31

3.2.3 Dead load existing piping............................................................................................... 32

3.2.4 Dead load new piping ..................................................................................................... 33

3.2.5 Horizontal pipe load (Anchor forces) ............................................................................ 34


3.2.6 Horizontal pipe loads (Friction forces .......................................................................... 34

3.2.7 Vertical truckload ............................................................................................................ 34

3.2.8 Wind load east west ........................................................................................................ 36

3.2.9 Wind load north south .................................................................................................... 37

3.2.10 Live load parking area 50 LBS per square foot ........................................................... 38

3.2.11 Wave forces extreme condition ..................................................................................... 39

3.2.12 Wave forces normal condition (Xdir) ............................................................................ 40

3.2.13 Loading arms dead weight ............................................................................................. 41

3.2.14 Loading arms wind force................................................................................................ 42

3.2.15 Gangway tower dead weight .......................................................................................... 43

3.2.16 Gangway tower wind force............................................................................................. 44

3.2.17 Uniform distributed load ................................................................................................ 45

3.2.18 Hawser pull ...................................................................................................................... 45

3.2.19 Breasting forces; ship impact load ............................................................................... 46

3.2.20 Temperature load ............................................................................................................ 47

3.2.21 Seismic load .................................................................................................................... 48

3.2.22 Self weight concrete collar ............................................................................................ 48

3.2.23 Self weight omitted concrete deck ................................................................................ 49

3.2.24 Seismic moment loading arms ...................................................................................... 50

3.2.25 Vehicle loading ................................................................................................................ 51

4 Load combinations ................................................................................ 53

5 Results .................................................................................................... 56

5.1 TRESTLE .......................................................................................................... 56

5.1.1 Design results ................................................................................................................. 56

5.1.2 Beam end forces summary ............................................................................................ 57

5.1.3 Maximum compression per pile .................................................................................... 59

5.2 LOADING PLATFORM A .................................................................................. 63


5.2.2 Minimum compression/ tension per pile ...................................................................... 65

5.2.3 Design results ................................................................................................................. 66

5.3 LOADING PLATFORM B .................................................................................. 67


5.3.2 Maximum compression per pile .................................................................................... 68

5.3.3 Minimum compression/ tension per pile ...................................................................... 69

5.3.4 Design results ................................................................................................................. 70

6 References ............................................................................................. 71

6.1 Reports ............................................................................................................. 71


6.2 Drawings .......................................................................................................... 71

Enclosures .......................................................................................................... 72


1 Introduction

XXXXwas requested by Shell Global Solutions to prepare a fit for purpose analysis of the existing gas jetty at XXXX. The gas jetty in the port of XXXX comprises two berths for the export of gas [LPG/LNG]. The objective of the project is to upgrade these jetties in line with a full rejuvenation scheme to enable an increase in terminal throughput and the receipt of LNG-carriers up to 75,000 m

3 as per 1 January 2009. This

rejuvenation scheme is based on the following activities:

temporary upgrading of a berth to meet the Jan-2009 milestone;

define and implement modifications to the jetty to guarantee safe loading operations for LPG and LNG carriers up to 7,000 m

3 and 75,000 m

3 capacity respectively.

The objective of the overall study is to:

Carry out a structural “fit for purpose” analysis of the existing jetty component;

Confirm design loads for the dolphins based on TERMSIM simulations and Shell design philosophy;

Structural analysis of new mooring and breasting dolphins. This report presents the structural fit for purpose analyses. For this study Scenario A is considered (the present situation). The layout of the two berths is outlined in Figure 1-1.

Figure 1-1 Berths locations Port XXXX

The fit for purpose analysis is carried out using the 3-D model STAAD. Separate models are made for the trestle, loading platform A and B and for all the dolphins. Secondly an analysis is done of the load factors of the construction determining the residual strength. In the following section first the setting up of the model is described in three parts: trestle, platform A, and platform B. The modelling of the dolphins is described in a different report [201].

Berth A

Berth B


2 3-D Modelling

As stated above, in this section the set up of the 3-D STAAD models is discussed. STAAD.PRO is a state of the art software model for 3-D model generation, finite element analysis and multi material design. Each of the three models is discussed separately in the sub sections: TRESTLE, PLATFORM A and PLATFORM B. In these sections the 3-D schematisation of the construction is discussed. The schematisation of the loads and the determination of the residual strength of the construction are discussed in sections 3 and 4 respectively.

2.1 TRESTLE

The modelling of the trestle is split in two parts, the substructure consisting of steel tubular pipes and steel beam pile caps, and the superstructure consisting of steel beam stringers interconnected with steel beams bracing. A figure of the framing of the superstructure can be found in APPENDIX A. The superstructure is laid on the pile cap in the model by using new nodes (A’, B’, etc). These nodes have the same X and Z coordinate as the underlying nodes (A, B, C, etc.). The Y coordinate has been increased. To position the stringer directly on top of the pile cap the elevation has to be increased by half the pile cap height and half the stringer height. The pile cap typically has a height of 590 mm and the stringer 640 mm. The elevation is (590+640)/2 = 615 mm. In Figure 2-1 an example of the elevation between the substructure and the superstructure is shown. To ensure a connection between the substructure and the superstructure in the model, the new nodes (A’, B’, etc.) have been made slave nodes to the nodes of the pile cap (A, B, etc), rigid in all directions.

Figure 2-1 Elevation between substructure and superstructure

PILE CAP

BRACING

ELEVATION

STRINGER

A

B

B’

A’

X

Y

Z


2.1.1 Substructure

Bents The substructure is made of 45 bents at 14 m spacing. Each bent consists of a set of piles and a pile cap. Depending of the function of the bent (being anchor bent or expansion joint) the piles are placed at a 1:3 angle or vertical. 4 types of pile caps can be identified being: Type 1: HE 600 A beam; Type 2: Box beam, assumed 600 mm by 600 mm with 20 mm wall thickness; Type 3: IPE 550 beam; Type 4: At bent 35 a jacket is placed; the construction and modelling of the jacket is discussed separately in section 2.1.3. In the following table, Table 2-1, a summary is given of the specifics for every bent. All bents are schematized accordingly. The bent types can be found in [307]. The cap type is described above and can also be found in [307].

bent no Type No of vertical piles No of batter piles cap elevation Seabed level Cap type

1 A 2 0 4120 1200 1

2 S 2 1 4150 0 2

3 A 2 0 4180 -300 1

4 Q 2 1 4210 -450 1

5 Q 2 1 4210 -600 1

6 A 2 0 4270 -800 1

7 E 0 10 4300 -100 2

8 Q 2 1 4330 -1200 1

9 Q 2 1 4360 -1400 1

10 Q 2 1 4390 -1600 1

11 A 2 0 4420 -1800 1

12 A 2 0 4450 -3000 1

13 L 1 6 4450 -4000 2

14 A 2 0 4450 -5000 1

15 A 2 0 4530 -6000 1

16 Q 2 1 4560 -6000 1

17 Q 2 1 4590 -6000 1

18 A 2 0 4620 -6000 1

19 A 2 0 4650 -6000 1

20 E 0 10 4680 -6000 2

21 A 2 0 4710 -6000 1

22 A 2 0 4740 -6000 1

23 M 2 2 4770 -6000 1

24 M 2 2 4800 -6000 1

25 A 2 0 4830 -6000 1

26 A 2 0 4860 -6000 1

27 G 0 6 4832 -6000 2

28 R 3 0 4832 -6000 1

29 B 2 0 4800 -6000 3

30 F 2 2 4770 -6000 1

31 F 2 2 4740 -6000 1

32 B 2 0 4710 -6000 3

33 K 1 3 4680 -6000 2

34 B 2 0 4650 -6000 3

35 JACK 3 0 4620 -6000 4

36 D 2 1 4590 -6000 1


37 B 2 0 4560 -6000 3

38 B 2 0 4530 -6000 3

39 J 0 8 4500 -6000 2

40 B 2 0 4470 -6000 3

41 B 2 0 4440 -6000 3

42 D 2 1 4410 -6000 1

43 D 2 1 4380 -6000 1

44 R 3 0 4322 -6000 1

45 G 0 6 4322 -6000 2

Table 2-1 summary of bents

Virtual fixity Since the pile end depth is not known with any certainty the pile end is schematized as a fixed support at a virtual depth. This depth (point of fixity, zf) can be determined using a stiffness factor T according to [101]. The stiffness factor T is 1651 mm, and the point of fixity (Zf) is 3000 mm. [See APPENDIX B1]. Accordingly the piles are assumed to be fixed at a distance of 3.0 m below the seabed. Piles All piles used are 16” steel piles with a 3/8” wall thickness. Expressed in millimetres this is an outside diameter of 406.4 mm and an inside diameter of 387.4 mm. Around the water level the piles are wrapped with a concrete layer with an outside diameter of 610 mm. The combined cross section of the concrete and steel pile is schematized as a steel pile with the same stiffness as the combined pile. In APPENDIX B2 the calculation is given which determines the outside diameter for the combined section. The dimensions of the collared pile are schematized as follows: Inside diameter (Di) = 387.9 mm Outside diameter (Do) = 456 mm. According to [301] the collar is located between +2.5 m and -2.5 m around MSL (el. + 0.00m). In the model the combined cross section is applied on the piles between el – 2.5 m and + 2.5 m. See Figure 2-2 for the schematisation of a bent. To account for the additional weight of the concrete collar a uniform distributed load is added on the section. The weight difference between the actual section and the model section is calculated in APPENDIX B4. In this calculation the different gravitational force above and below water is taken into account. The weight difference between the actual cross section and the modelled cross section is 3.08 kN. This difference acts on the total length of the pile, which is 5 m. The distributed load added in the model therefore is 3.08/5 = 0.61 kN/m.


Figure 2-2 Schematisation of steel piles

2.1.2 Superstructure

The trestle superstructure consists of a series of stringers and braces. The stringers span 14 meter between each bent and are all HE 650 A members. Connecting the stringers are 3 meter long IPE 400 beams at the location of the bents and ½ IPE 330 beams at 3.5 meter intervals between the bents. The braces in diagonal direction are also ½ IPE 330 beams. In the model the ½ IPE 330 beams are replaced by full IPE 330’s in order to correctly model the stiffness of the structure. The ½ IPE 330 beams are connected to the stringers in such a way that they can not take moment forces and high compression loads. Part of the compression forces will be taken by the concrete deck. Since the deck is not part of the model this force should be taken by the braces. To make sure the braces are able to take the load full IPE beams in stead of ½ IPE beams are assumed. All the braces are modelled with moment releases at each end indicating that they can take forces but no moments. Expansion joints The expansion joints in the superstructure are schematized as releases in the stringers. When the beams are released completely in X direction (normal to the beam) deflections can occur in the model that are larger than possible in reality. As can be seen from Figure 2-3 the expansion joint exists of a slot of 60 mm wide. This indicates that only 30 mm in each direction is possible. This effect is initially neglected in the model and the releases are released fully in x direction. In section 5 the result of this assumption is discussed in more detail. Reference is made to [302] for an overview of the location of the expansion joints.

BATTER PILE

VERTICAL PILE

EL + 2.5 m

EL. – 2.5 m

COLLAR

POINT OF FIXITY


Figure 2-3 Expansion joint detail [306]

Concrete walkway The concrete walkway on top of the stringers is schematized as a superimposed dead load and will be discussed in the loads section. All other constructional elements are considered negligible

2.1.3 Jacket @ Bent 35

At bent 35 a jacket is located. The jacket consists of three steel piles with ø 18” and 20” piles and ø 219 mm bracing. Around the water level the ø 18” piles are wrapped with a ø 660 mm concrete collar ranging from el -1.0 m to el. + 1.3 m. The 20” pile is also wrapped with a ø 660 mm concrete collar ranging from el -1.0 m to el. + 3.5 m. No wrapping is assumed round the bracing [301]. The jacket is held in place by the same 18” steel pipes that support the trestle. These pipes are driven through the piles of the jacket and fixated with a filling of concrete. The combined cross-section of the jacket piles therefore consists of steel pile, concrete filling and outer steel pile. The combined cross section of the concrete and steel pile is schematized as a steel pile with the same stiffness as the combined pile. In APPENDIX B3 the calculation is given which determines the outside diameter for the combined section. The dimensions of the steel jacket piles are schematized as follows: 18“ pile Inside diameter (Di) = 387.9 mm Outside diameter (Do) = 433.5 mm


20” pile Inside diameter (Di) = 387.9 mm Outside diameter (Do) = 449.3 mm As described these piles are wrapped with a concrete collar around the waterline. The combined cross section of the concrete and steel pile is schematized as a steel pile with the same stiffness as the combined pile. In APPENDIX B.4 the calculation is given which determines the outside diameter for the combined section. The dimensions of the collared pile are schematized as follows: 18” pile Inside diameter (Di) = 387.9 mm

Outside diameter (Do) = 487.2 mm 20” pile Inside diameter (Di) = 387.9 mm Outside diameter (Do) = 491.9 mm. The ø 219 mm bracing is assumed to have an inside diameter of 210 mm (wall thickness is 4.5 mm). For more detail on the dimensions of the jacket reference is made to drawing [304]. In Figure 2-4 the model schematisation of the substructure of bent 35 is shown.

Figure 2-4 Model schematisation of Jacket @ bent 35


2.2 LOADING PLATFORMS

Since an expansion joint is located at bent 46 as well as bent 49 [see APPENDIX A] the loading platforms can be schematized separately from the trestle. In this section loading platform A is discussed. In the schematisation of the platform the parking area is included in the model. The parking area is supported by three bents with similar construction as the trestle bents. The loading platform itself is supported by vertical and batter piles capped with steel beams (both standard and manufactured beams). The superstructure consists of a series of stringers and braces with a concrete surface on top. In the following subsections the sub- and superstructure are described in more detail. The superstructure is laid on the pile cap in the model by using new nodes (A’, B’, etc). These nodes have the same X and Z coordinate as the underlying nodes (A, B, C, etc.). The Y coordinate has been increased. To position the stringer directly on top of the pile cap the elevation has to be increased by half the pile cap height and half the stringer height. The pile cap has varying heights between 550 mm and 836 mm. The stringers typically have a height of 500 mm. The elevation is (836+500)/2 = 669 mm.

Figure 2-5 Elevation of superstructure above substructure

In Figure 2-5 an example of the elevation between the substructure and the superstructure is shown. To ensure a connection between the substructure and the superstructure in the model, the new nodes (A’, B’, etc.) have been made slave nodes to the nodes of the pile cap (A, B, etc), rigid in all directions.

2.2.1 Substructure parking area platform A

As described above the substructure of the parking area and the platform differs slightly. The substructure

A

A’

ELEVATION

STRINGER

PILE CAP


of the parking area consists of 3 bents with the following specifics, Table 2-2.

bent no bent type No of vertical piles No of batter piles cap elevation Bottom elevation Cap type

46 N 3 1 4286 -6000 1

47 T 3 0 3825 -7500 1

48 T 3 0 3364 -8100 1

Table 2-2 substructure parking area platform A

The cap elevation of the loading platform is assumed to be at the same level as bent 48. The bottom level is assumed to be at el – 9.00 m.

2.2.2 Substructure parking area platform B

Platform B is very similar to platform A. Differences can be found in the structure of the parking area. The supporting bents are of a different type and also the surface of the parking area is different. The loading platform itself however is exactly the same, although shifted slightly in the longitudinal direction. The substructure of the parking area consists of 3 bents with the following specifics, Table 2-3.

bent no Type No of vertical piles No of batter piles cap elevation Bottom elevation Cap type

49 P 3 1 4834 -6000 1

50 C 3 0 4869 -9000 1

51 U 2 0 4904 -11400 1

Table 2-3 Summary of bent characteristics

The cap elevation of the loading platform is assumed to be at the same level as bent 51. The bottom level is assumed to be at el – 11.40 m.

2.2.3 Substructure platforms

The substructure of the platform also consists of a series of vertical and batter piles but in a different scheme. The vertical piles are placed in rows of 5 piles with 4.6 and 6.0 m spacing [Figure 2-6]. The batter piles are placed in the centreline of the platform as shown in Figure 2-6. Capping the longitudinal series of batter piles is a combined member designated “member B” (highlighted in Figure 2-6 by the orange colour) and connecting with the vertical piles “member C” (highlighted by the yellow colour). The transverse batter piles and the four vertical piles in the transverse centreline are capped by a combined member designated “member A”, highlighted by the green colour.


Figure 2-6 Framing plan Loading platform

The pile cap of the remaining vertical piles consists of IPE 550 beams. The point of fixity of the piles is taken at the same depth as for the piles of the trestle (3.00 m below seabed) MEMBER A Member A is a combined member consisting of an IPE 550 beam supported by a welded I beam with a web of 1200 mm by 13 mm and flanges of 300 by 20 mm. In APPENDIX B5 figures as well as the combined beam characteristics are given. In STAAD the member is schematized as an IPE 550 beam with a rectangular bottom plate. The bottom plate is calculated to have the same stiffness in Y and Z direction as the I-beam which it replaces. In APPENDIX B5 the calculation of the stiffness of the bottom plate can be found. A bottom plate is used in the model with a width of 893.7 mm and a thickness of 106.55 mm. Since the area of the plate is 4 times larger than the I-beam it replaces, the stiffness of the beam is exaggerated. However, analysis with the IPE beam only (without bottom plate) indicated that the beam had sufficient strength; therefore the above described schematisation is assumed acceptable. In Figure 2-7 the modelled schematisation of “member A” is shown.


Figure 2-7 Schematisation of “Member A”

MEMBER B Member B consists of a HE A 400 beam supported by a welded I beam with a web of 1200 mm by 13 mm and flanges of 300 mm by 18 mm. In APPENDIX B5 figures as well as the combined beam characteristics are given. Similar to Member A the welded I beam is replaced by a rectangular bottom plate in the model. Since the I-beam has the same dimensions as Member A the bottom plate also has the same dimensions. For this schematisation the same limitation holds as for Member A. In this case analysis also showed that the single HE 400 A beam had sufficient strength to bear the loads. Therefore the above described schematisation is used since it leads to a safe estimate of the forces on the piles. MEMBER C Member C is a welded I beam with a web of 800 mm by 13 mm and flanges of 210 mm by 18 mm. In APPENDIX B5 pictures as well as the beam characteristics are given. In STAAD the member is schematized as a wide flanged member with the following specifics, see Figure 2-8.

Figure 2-8 Input screen MEMBER C


2.2.4 Superstructure

The platforms superstructure consists of a series of stringers and braces. Stringers can be both HE A 500 or IPE 450 beams, whereas braces are HE B 220 beams. All braces are modelled as tension only members. The parking area’s superstructure also consists of a series of stringers and braces. The stringers span 14 meter between each bent and are all HE 650 A members. Connecting the stringers are IPE 400 beams at the location of the bents and ½ IPE 330 beams at 3.5 meter intervals between the bents. The braces in diagonal direction are also ½ IPE 330 beams. The braces are schematized in the model as normal full IPE 330 members with moment releases at each end. In Figure 2-9 an aerial view of the structure of the parking area is shown. Indicated in red are the stringers. Between the stringers are braces and below the stringers are the pile caps. The braces in the parking area and platform area are modelled with releases. The members can only take axial and shear forces and are not loaded with moments.

Load 101

Figure 2-9 Arial view of steel structure parking area

Concrete walkway The concrete walkway on top of the parking area is schematized as a superimposed dead load and will be discussed in the loads section. The concrete roadway on top of the platform itself is schematized as a series of plates connected with the underlying beams. On top of the concrete planks an overlay of 65 mm is assumed. The concrete is modelled as a slab with a thickness of 165 mm + 65 mm = 230 mm. The concrete slab on the loading platform is 0.80 m smaller in transverse direction and 0.30 m shorter in longitudinal direction in the model than in reality, see Figure 2-6 where platform extends 0.40m and 0.15 m on the front and side of the framing of the platform. To accommodate for the difference in dead weight of the omitted concrete an extra load is added on the platform models. Reference is made to 3.2.23 for a description of the load. All remaining superstructure is not modelled as construction element. The loading arms are schematized as forces, discussed in the forces section. All other construction elements are schematized as a superimposed uniform distributed load, also discussed in the loads section.


3 Loads

3.1 TRESTLE LOADS

In this section the loads acting on the construction are discussed. These loads are implemented in the model in order to assess the residual strength of the structure.

3.1.1 Self weight construction

The self weight of the construction is calculated by the model itself based on the modelled elements. Elements that are not a part of the model will be added as a superimposed dead weight (3.1.2) or as a uniform distributed Load (3.2.17).

3.1.2 Deadweight concrete roadway

The deadweight of the concrete roadway on the trestle and parking areas can not be calculated by the model as it is not part of the model. Therefore an extra superimposed deadweight will be added. The concrete deck is assumed to be 3.60 m wide, with 250 mm curbs and a thickness of 165 mm (on the trestle and parking areas of the platforms, no overlay is assumed). The total concrete volume of the roadway (Ac) = 719,000 mm

3/mm. The corresponding load acting on each of the stringers is 8.8 kN/m

1 (density concrete

is assumed to be 24.5 kN/m3). In Figure 3-1 a part of the trestle is shown with the load of the concrete

roadway acting upon the stringers.

Figure 3-1 Schematisation of dead load concrete roadway


3.1.3 Dead load existing piping

The deadweight of the gas and water pipes (including contents) located on the trestle and platforms is also added as a superimposed load. The existing piping is schematised as 3 pipes of different diameter:

1. 22” LNG pipe 2. 16” LNG return pipe 3. 6” LPG + 3” LPG return + 8” Firewater

The pipes are assumed to be schedule 40 pipes [104] with the following characteristics, see Table 3-1.

Diameter [inch] Outside diameter [mm] Wall thickness [mm] Weight [kg/m]

3 88.9 4.78 9.91

6 168.3 7.11 28.26

8 291 8.18 42.53

16 406.4 12.70 123.29

22 558.8 15.88 212.52

Table 3-1 schedule 40 existing pipe characteristics

The pipes are assumed to be either filled with LNG [5 kN/m

3], LPG [6.5 kN/m

3], water [10 kN/m

3] or air/gas

[0 kN/m3]. The pipes are supported every 14 m by the bents. Every bent therefore carries 14 m of pipe. On

every bent the following pipe loads are modelled as concentrated loads for the existing pipelines. The LNG and LPG pipes are assumed filled with liquid gas with the specific weights as given above. The return pipes are assumed to be filled with gas and or air and the specific weight is assumed to be zero (0 kN/m

3).

1. 22” LNG pipe, filled with liquid gas, F = 44.4 kN; 2. 16”LNG gas return pipe filled with gas and air, F = 16.9 kN; 3. 6” LPG filled with liquid gas, 3” LPG filled with gas + 8” Firewater filled with water, F = 15. 2 kN.

In Figure 3-3 the general position of the pipelines on the trestle is shown. The existing pipelines are all located on the landward side of the trestle. From bent 1 to bent 45 the position of the pipelines on the trestle is constant. At bent 28 and onward the pile cap is 200 mm smaller than before. Therefore the distance of the centreline of the pipe to the end of the pile cap is also smaller. In Table 3-2 and Table 3-3 summations of the locations of the pipelines on the pile caps are given. The starting location is at the most left part of the pile cap, so the first pipe is located at 1300 mm to the right of the leftmost end of the pile cap. In Figure 3-2 a part of the trestle is shown with the dead load of the existing piping acting on the model. These loads are acting on all the bents of the trestle.

Figure 3-2 Schematisation of dead load existing piping


Figure 3-3 cross section of trestle with existing and new Pipelines [202]

Pipe Distance to start point Distance to previous pipe Distance to next pipe

1 1300 mm - 1300 mm

2 2600 mm 1300 mm 1100 mm

3 3700 mm 1100 mm -

Table 3-2 location of existing pipelines on bents 1 to 27


1 1100 mm - 1300 mm

2 2400 mm 1300 mm 1100 mm

3 3500 mm 1100 mm -

Table 3-3 location of existing pipelines on bents 28 to 46

The above given positions are used in the model for the position of the concentrated loads schematizing the dead weight of the existing pipelines.

3.1.4 Dead load new piping

In APPENDIX C the position of the existing pipelines and the new pipelines is given. In the future situation the LNG pipelines at the trestle between platforms A and B will be removed and replaced by a much smaller series of LPG pipelines. Since the dead weight of the existing pipelines is normative for the strength calculation of the trestle, in the new situation the removal of the LNG pipelines is neglected. Between platform A and the shore however, a new series of LNG and LPG pipelines is added on the seaward side of the trestle. This load will be schematised as extra concentrated loads for the new situation. The new pipelines are schematized as follows

4. 20”LNG pipe 5. 12” LPG pipe 6. 6” LPG return + 8” firewater


The pipes are assumed to be schedule 40 pipes [202] with the following characteristics, see Table 3-4

Diameter [inch] Outside diameter [mm] Wall thickness [mm] Weight [kN/m]

6 168.3 7.11 28.26

8 291 8.18 42.53

12 323.8 10.31 79.72

20 508 15.06 183.05

Table 3-4 schedule 40 new pipe characteristics

The pipes are assumed to be either filled with LNG [5 kN/m3], LPG [6.5 kN/m

3], water [10 kN/m

3] or air/gas


every bent the following pipe loads are modelled as concentrated loads for the new pipelines 4. 20” LNG pipe, filled with liquid gas, F = 37.9 kN; 5. 12”LPG pipe filled with liquid gas, F = 11.872 kN; 6. 6” LPG filled with gas and air + 8” Firewater filled with water, F = 15. 2 kN.

In Figure 3-3 the general position of the pipelines on the trestle is shown. The new pipelines are located on the seaward side of the trestle. From bent 1 to bent 27 the position of the new pipelines on the trestle is constant. At bent 28 and onward the existing pipe load is assumed. In Table 3-5 a summation of the locations of the pipelines on the pile caps is given.


4 1300 mm - 1300 mm

5 2600 mm 1300 mm 1100 mm

6 3700 mm 1100 mm -

Table 3-5 location of new pipelines on bents 1 to 27

In Figure 3-4 the dead load of the piping is shown acting on the model.

Figure 3-4Schematisation of dead load new piping

3.1.5 Horizontal pipe load (Anchor forces)

The piping can exert horizontal forces on the bents as a result of pressure built up inside the piping. The pipes are fixed at the anchor bents and are able to expand at the expansion loops, the bend in the trestle at bent 13 and the loop crossing the trestle at bent 27. Anchor bents are located at bents 7, 20 and 39. At the anchor bents the piping exerts a force at the bent. It is assumed that the force acts on the bents in one direction. This force is schematised as a concentrated load acting at the same place as the


deadweight of the 22” LNG pipeline working perpendicular to the bent as shown in Figure 3-5. The magnitude of the force is described in [304] as 70 KIPS, which corresponds to 311 kN. It is assumed that this load includes temperature loads in the piping, since the piping is not a part of the model no further temperature load will be added.

Figure 3-5 Schematisation of pipeline anchor forces on trestle

3.1.6 Horizontal pipe loads (Friction forces

At the non anchor bents the pipeline exerts a friction force at the bents as the pipeline slides over the support. This force is assumed to act towards the anchor bents from both sides. This force is schematised as a concentrated load acting at the same place as the deadweight of the 22” LNG pipeline working perpendicular to the bent. In Figure 3-6 part of the trestle is shown with the pipeline friction forces indicated by the arrows.

Figure 3-6 Schematisation of friction forces on trestle

The magnitude of this load is described in [304] as 2.4 KIPS, which corresponds with 10.7 kN. This force is


applied on all bents except bents 7, 13, 20, 27 and 38. It is assumed that this load includes temperature loads in the piping, since the piping is not a part of the model no further temperature load will be added.

3.1.7 Vertical truckload

In [304] it is indicated that the trestle is designed for a truckload: AASHO H20 S44. It is assumed that the truck load HS 20-44, according to AASHTO [102] is indicated here. This loading incorporates a 20 tons tractor truck with semitrailer. The axel loads are given according to APPENDIX E. This load acts on the concrete roadway on top of the trestle. Since the roadway is not incorporated into the model the load has to be transferred to the stringers which support the roadway. The roadway is made out of 1 m wide sections and it is tentatively assumed that the concrete spreads the axel loads over its full width, see Figure 3-7 The load acting on the stringers is therefore schematized as three distributed loads acting on 1 m sections of the beam. Over a 14 meter long section of the stringer (the span between two bents) the loads are applied as follows: F1 = 35.6 kN/m location 2000 mm to 3000 mm of beam starting point F2 = 142.4 kN/m location 7000 mm to 8000 mm of beam starting point F3 = 142.4 kN/m location 12000 mm to 13000 mm of beam starting point (1 LBS = 4.45 N)

Figure 3-7 Schematisation truck load on trestle

3.1.8 Wind load east west

In [304] it is indicated that the design of the trestle should be able to withstand a wind load of 12 LBS/ft2 in

the east west direction. This load should be applied to the superstructure of the trestle. The superstructure of the trestle consists of the stringers and the concrete roadway. On top of the roadway a handrail and


piping are situated. Combined they have a height of 2255 mm (640 mm for the stringers, 1200 for the handrail and pipe rack and 165 + 250 mm for the roadway). It is assumed that the wind load acts perpendicular to the first part of the trestle (bent 1 to 13, which has a more or less north to south orientation) and has no effect on the second part (Bent 14 to 45), see Figure 3-8. The wind load is schematized as a uniform distributed load acting on the stringers. The magnitude of the load can be calculated as follows:

12 LBS/ft2 equals 574 N/m

2

Area equals 2255 mm2/mm

Load equals 574 n/m2 * 2255 mm

2/mm = 1.29 N/mm

1

Figure 3-8 schematisation wind load east west on trestle

3.1.9 Wind load north south


the north south direction acting on the superstructure and 40 LBS/ft2 in the north south direction acting on

the substructure. The first load should be applied to the superstructure of the trestle. The superstructure of the trestle consists of the stringers and the concrete roadway. Combined they have a height of 1055 mm (640 mm for the stringers and 165 + 250 mm for the roadway). The second load should be applied to the substructure of the trestle, which consists of steel piles with a concrete collar. The piles have width of 610 mm at the concrete collar and a width of 406 mm above that. It is assumed that both sections have a height of 2500 mm. The combined surface is therefore 2.54 * 10

6

mm2.

It is assumed that the wind load acts perpendicular to the second part of the trestle (bent 14 to 45, which has a more or less east to west orientation) and has no effect on the first part (Bent 1 to 13). The wind load on the superstructure is schematized as a uniform distributed load acting on the stringers (blue arrows in Figure 3-9) and the wind load on the substructure is schematized as concentrated forces acting on the node between the pile and the pile cap shown by the green arrows in Figure 3-9. The magnitude of the load on the superstructure can be calculated as follows:



2

Area equals 1055mm2/mm


2/mm = 2.42 N/mm

1

The magnitude of the load acting on the substructure can be calculated as follows:


2

Area equals 2,541,000 mm2

Load equals 1915 n/m2 * 2,541,000 mm

2 = 4866 N

.

Figure 3-9 Schematisation of wind load north south on trestle

3.1.10 Live load

According to [304] a live load of 50 LBS per square feet should be applied on the trestle. This load is applied in the model at an arbitrary part of the trestle between two bents. A load of 50 LBS/ft

2 corresponds

with a load of 2.39 kN/m2. The area the load works on is the full with of the walkway (3.6 m) the walkway

exerts the same load onto the underlying Stringers. Hence this load is applied on the stringers as a uniform distributed load of 2.39 kN/m

2 * 0.5 * 3.6 m

2/m

1 = 4.3 kn/m

1 as shown in Figure 3-10.


Figure 3-10 Schematisation of live load on trestle

3.1.11 Wave forces extreme condition

The trestle is located more or less perpendicular to the harbour entrance. It is therefore assumed that waves encounter the trestle at a 90° (perpendicular) angle. This holds for the second part (bents 14 to 45) of the trestle. The first part (shore to bent 13) is assumed to be sheltered from waves by the second part and the platforms. Based on [203] an extreme wave height (Hs) just in front of the trestle of 1.84 m is to be expected. This is similar to the wave height indicated in [304]. With a depth at the trestle of 6 m and a wave period of 10 s the wave load on the piles can be calculated. This is done using RFWAVE and RF force, APPENDIX F. RFWAVE uses the Hmax which is equal to 1.8 times the Hs. Since the piles have two dimensions, 406 mm for the first 3.5 m and 610 mm for the part above that (with collar) two different runs of RF Force have been done (APPENDIX F). The applied wave load on the piles is combined using the wave load on the 406 mm pile for the first 3.5 m and the wave load on the wider section on the upper part. This leads to the following load distribution on the pile, see Table 3-6:

level total Force

mm kN/m

-6000 0.87

-2500 1.08

-2500 1.63

2640 5.01

Table 3-6 Wave forces Trestle extreme condition, hmax = 3.31 m

The same force is applied on all the trestle piles, including the batter piles. The batter piles have a longer shaft length but because the applied force acts over a specified length the force is equal in size as on the vertical piles. The only exception is bent 14, where the depth is only 5.5 m. Here the same load is applied only over a shorter length of the pile, compensating for its shorter length. In Figure 3-11 a typical part of the trestle is shown with the wave forces acting on the piles in the global X direction.


Figure 3-11 Schematisation of wave forces

Although wave crests can come in close proximity of the trestle underside no wave uplifting force is assumed on the superstructure.

3.1.12 Wave forces normal condition

In the normal case a wave height just in front of the trestle of 1.01 m (HS) is assumed, [203]. This is larger than the wave height indicated in [304]. With a depth at the trestle of 6 m and a wave period of 10 s the wave load on the piles can be calculated. This is done using RFWAVE and RF force [APPENDIX F]. RFWAVE uses the Hmax which is equal to 1.8 times the Hs. Since the piles have two dimensions, 406 mm for the first 3.5 m and 610 mm for the part above that (with collar) two different runs of RF Force have been done (APPENDIX F). The applied wave load on the piles is combined using the wave load on the 406 mm pile for the first 3.5 m and the wave load on the wider section on the upper part. This leads to the following load distribution on the pile, see Table 3-7:

level total Force

mm kN/m

-6000 0.36

-2500 0.43

-2500 0.71

1220 1.22

Table 3-7 Wave forces Trestle normal condition, hmax = 1.82 m

The same force is applied on all the trestle piles, including the batter piles. The batter piles have a longer shaft length but because the applied force acts over a specified length the force is equal in size as on the vertical piles. The only exception is bent 14, where the depth is only 5.5 m. Here the same load is applied


only over a shorter length of the pile, compensating for its shorter length.

3.1.13 Temperature load

As a result of temperature variation loads can occur within the construction. To model this load a temperature load is added to the model. In [304] temperature variations are stated to be between 35° F and 110° F. This corresponds to 274° K and 316 ° K. Since it is unclear whether the ambient temperature or the construction temperature is described here engineering practice is used to determine the temperature variations that can occur. The temperature load is added only to the upper part of the model (the piles are almost completely below water level where temperature fluctuations are significantly smaller). Assuming that the construction is build in winter (average temperature is 15°C) and heats up in summer (60°C) a positive temperature variation of 45° can occur Assuming that the construction is build in moderate temperatures (36°C) and cools down in winter (15°C) a negative temperature variation of 21° can occur. In Figure 3-12 part of the trestle is shown with the temperature load indicated by blue arrows. The temperature load is only added to the part of the structure that is expected to take part in the distribution of the load.

Figure 3-12 Schematisation of temperature load on trestle


3.1.14 Seismic load

Since Libya is a seismically active area the model should include Seismic loads. Seismic load can be defined using the UBC 1997 [103]. UBC 1997 load definitions requires the following input parameter:

1. Seismic zone coefficient, Libya is in zone 2A, Zone is 0.15; 2. Importance factor, we are dealing with hazardous facilities, I = 1.25; 3. Numerical coefficient R for lateral load in X: jetty is a non building structure, R = 2.9; 4. Numerical coefficient R for lateral load in Z: jetty is a non building structure, R = 2.9; 5. Soil profile type: assumed is a stiff soil profile, type SD, STYP = 4; 6. Near source factor Na, Na = 1 7. Near source factor Nv, Nv = 1

The seismic calculation uses the weight loads to calculate the resulting seismic force on the structure. The weights used in this trestle model are:

1. self weight of trestle construction 2. self weight concrete roadway 3. self weight piping

With these parameters entered into the model, STAAD calculates a seismic load in both the X and the Z direction. These loads are used in several load combinations to determine the residual strength of the Trestle. Besides horizontal seismic forces also a vertical seismic force should be taken into account. According to [103] the vertical component of the seismic load can be calculated as follows: EQ (Y) = 0.5 *Ca * I * D, where: - Ca (seismic coefficient of soil type and zone) = 0.22 - I (importance factor) = 1.25 - D = dead weight of construction in kN It follows that the horizontal component of the seismic force can be calculated by multiplying the dead load by 0.1375, see Table 3-8 for the input parameters for the vertical seismic component.

Dead weight type: Force (Y) Seismic force (Y)

Concrete roadway 8.8 kN/m 1.21

Concrete collar 0.61 kN/m 0.08

Existing 22” LNG pipe 44.4 kN 6.11

Existing 16” LNG return pipe 16.93 kN 2.33

Existing smaller pipes 15.92 kN 2.09

New 20” LNG pipe 37.89 kN 5.21

New 12” LPG pipe 11.87 kN 1.63

Table 3-8 Seismic forces related to dead weights

3.1.15 Dead weight concrete collar on piles

As is already explained in section 2.1.1 the modelled cross section of the piles, in combination with the concrete collar neglects the dead weight difference. This difference in dead load is remedied in the model by adding a uniform distributed load of 0.61 kN/m. This load is added to the piles as shown in Figure 3-13.


Figure 3-13 Schematisation dead load of concrete collars on piles

3.1.16 Vehicle loading

Vehicle loading is assumed according to BS 5400. A nominal HB loading is analysed to be acting on different parts of the trestle. The shortest wheelbase is assumed to give the most severe effect. Analyses showed that the vehicle load had the greatest effect on pressure and tension in the platform piles as shown in the following figures. Figure 3-14 show the location of the vehicle load on the trestle for maximum tension in the piles, Figure 3-15 shows the position of the vehicle load for maximum pressure.

Figure 3-14 Vehicle load for maximum tension

Tension


Figure 3-15 vehicle load for maximum pressure

Pressure


3.2 LOADING PLATFORMS

In this section the loads on the loading platforms are discussed. These loads are implemented in the models in order to assess the residual strength of the structure. With respect to the trestle extra loads have been applied due to the loading arms and gangway tower. Most of the forces acting upon the model are similar for platform A and platform B. Wave forces however, have different magnitudes for either location. This will be discussed in section 3.1.11 and 3.2.12. the same goes for the loading arms. On platform A the existing loading arms will be taken into account. On platform B the loading arms will be replaced. This is discussed in 3.2.13 and 3.2.14.

3.2.1 Self weight construction

The self weight of the Platform construction is calculated by the model itself based on the modelled elements. Elements not in the model will be added as a superimposed dead weight (3.2.2) or as a uniform distributed Load (3.2.17).

3.2.2 Deadweight concrete roadway

The deadweight of the concrete roadway on the parking area can not be calculated by the model as it is not part of the model. Therefore an extra superimposed deadweight will be added. The concrete deck is assumed to be 3.00 m wide with 250 mm curbs and a thickness of 165 mm (on the trestle and parking areas of the platforms, no overlay is assumed). The corresponding load acting on each of the stringers is 7.3 kN/m

1, see 3.1.2. Since the parking area spans on two sides of the middle stringers, they bear double

the load; 14.6 kN/m1. In Figure 3-16 the schematised load is shown added to the model of platform B. The

green arrows represent the load on the middle stringers which is double.

Figure 3-16 Load due to dead weight of concrete roadway and parking area on platform B


3.2.3 Dead load existing piping

The deadweight of the gas and water pipes (including contents) located on the trestle and platforms is also added as a superimposed load. The existing piping is schematised as 3 pipes of different diameter:

1. 22” LNG pipe 2. 16” LNG return pipe 3. 18”RLPG pipe 4. 6” LPG + 3” LPG return + 8” Firewater

The pipes are assumed to be schedule 40 pipes [104] with the following characteristics, see Table 3-1

Diameter [inch] Outside diameter [mm] Wall thickness [mm] Weight [kg/m]

3 88.9 4.78 9.91

6 168.3 7.11 28.26

8 291 8.18 42.53

16 406.4 12.70 123.29

18 457.2 14.27 155.91

22 558.8 15.88 212.52

Table 3-9 schedule 40 existing pipe characteristics

The pipes are assumed to be either filled with LNG [5 kN/m

3], LPG [6.5 kN/m

3], water [10 kN/m

3] or air/gas


every bent the following pipe loads are modelled as concentrated loads for the existing pipelines 1. 22” LNG pipe, filled with liquid gas, F = 44.4 kN; 2. 16”LNG gas return pipe filled with gas and air, F = 16.9 kN; 3. 18”RLPG filled with liquid gas, F = 34.5 kN; 4. 6” LPG filled with liquid gas, 3” LPG filled with gas + 8” Firewater filled with water, F = 15.2 kN.

In Figure 3-17 the general position of the pipelines on the trestle is shown. The existing pipelines are all located on the western side of the parking area. In Table 3-10 a summation of the locations of the pipelines on the pile caps are given. The 18”RLNG pipeline is assumed at the same position of the smaller LPG and service pipes.


1 1300 mm - 1300 mm

2 2600 mm 1300 mm 1100 mm

3 & 4 3700 mm 1100 mm -

Table 3-10 Location of existing pipeline on parking area bents

The above given positions are used in the model for the position of the concentrated loads schematizing the dead weight of the existing pipelines. In Figure 3-18 a schematisation is shown of the vertical pipe loads in the model.


Figure 3-17 cross section of trestle with existing and new Pipelines [202]

Figure 3-18 Schematisation of pipe loads on the model of platform B

3.2.4 Dead load new piping

On the platforms no new piping is modelled since the current situation is normative.


3.2.5 Horizontal pipe load (Anchor forces)

The piping can exert horizontal forces on the bents as a result of pressure built up inside the piping. The pipes are fixed at the anchor bents and are able to expand at the expansion loops, the bend in the trestle at bent 13 and the loop crossing the trestle at bent 27. Anchor bents are located at bents 7, 20 and 39. Since the bents under the parking area as well as the platform are not anchor bents, no anchor force is modelled on the platform.

3.2.6 Horizontal pipe loads (Friction forces

At the non anchor bents the pipeline exerts a friction force at the bents as the pipeline slides over the support. This force is assumed to act towards the anchor bents from both sides. This force is schematised as a concentrated load acting at the same place as the deadweight of the 22” LNG pipeline working perpendicular to the bent. The magnitude of this load is described in [304] as 2.4 KIPS, which corresponds with 10.7 kN. This force is applied on all bents underneath the parking area of both platforms. In Figure 3-19 a schematisation is shown of the horizontal pipe forces in the model of platform B.

Figure 3-19 schematisation of horizontal pipe forces on platform B

3.2.7 Vertical truckload

In [304] it is indicated that the governing load for the loading platform should be determined between a truckload: AASHO H20 S44 and a 400 LBS per square foot live load. It is assumed that the truck load HS


20-44, according to AASHTO [102] is indicated here. This loading incorporates a 20 tons tractor truck with semitrailer. The axel loads are given according to APPENDIX E. To determine the normative loads, the total load of the truck is determined as well as the total load of the live load acting the concrete deck between two bents.

The truck load measures: 35.6 kN + 142.4 kN + 142.4 kN = 320.4 kN per side is 641 kN in total.

The live load acts on an area of 3.60 m by 14 m and has a load of 400 lbs/ft2 (19.152 kN/m

2. the

total live load equals 965 kN The live load of 400 LBS is the governing load. It is assumed that this loads acts on the parking area of the platform, see Figure 3-20 for the schematisation of the load on platform B and Figure 3-21 for the schematisation on platform A.

Figure 3-20 Schematisation of truck/live load on parking area of platform B


Figure 3-21 Schematisation of truck/live load on parking area of platform A

3.2.8 Wind load east west


the east west direction. This load should be applied to the superstructure parking area of platform A. The superstructure of the parking area consists of the stringers, hand rail and pipe rack and the concrete roadway. Combined they have a height of 2255 mm (640 mm for the stringers, 1200 for the hand rail and pipe rack and 165 + 250 mm for the roadway). The platform superstructure consists of stringers, high members and a concrete roadway. On the outside they have a height of 1465 mm (550 mm + 500 mm + 165 mm + 250 mm. The middle part of the platform has a combined height of 1751 mm (836 mm +500 mm + 165 mm + 250 mm). It is assumed that the wind load acts perpendicular to parking area (bent 49 to 51), which has a more or less north to south orientation) and also on the loading platform itself. The wind load is schematized as a uniform distributed load acting on the stringers as shown in Figure 3-22. The magnitude of the load on the parking area can be calculated as follows:


2

Area equals 2255 mm2/mm


2/mm = 1.29 N/mm

1

The magnitude of the load on the loading platform can be calculated as follows:


2

Outer area equals 1465 mm2/mm

Outer load equals 574 n/m2 * 1465 mm

2/mm = 0.841 N/mm

1

Middle area equals 1751 mm2/mm

Middle load equals 574 n/m2 * 1751 mm

2/mm = 1.005 N/mm

1


Figure 3-22 Schematisation of wind load east west

3.2.9 Wind load north south

In [304] it is indicated that the entire structure should be able to withstand a wind load of 50 LBS/ft2 in the

north south direction acting on the superstructure and 40 LBS/ft2 in the north south direction acting on the

substructure. The first load should be applied to the superstructure of the loading platform. The platform superstructure consists of stringers, combined members and a concrete roadway. On the outside they have a height of 915 mm (500 mm + 165 mm + 250 mm. The middle part of the platform has a combined height of 1715 mm (800 mm +500 mm + 165 mm + 250 mm). The second load should be applied to the substructure of the platform, which consists of steel piles with a concrete collar. The piles have width of 610 mm at the concrete collar and a width of 406 mm above that. It is assumed that the bottom section has a height of 2500 mm and the top section a height of 1400mm. The combined surface is therefore 2.09 * 10

6 mm

2.

It is assumed that the wind load acts perpendicular to the north side of the loading platform, which has a more or less north to south orientation) and has no effect on the parking area. The wind load on the superstructure is schematized as a uniform distributed load acting on the stringers and the wind load on the substructure is schematized as concentrated forces acting on the node between the pile and the pile cap, see Figure 3-23. In this figure the load on the piles is schematised by the blue arrows acting on the top of the piles. The magnitude of the load on the superstructure can be calculated as follows:


2

Middle area equals 915 mm2/mm

Middle Load equals 2394 n/m2 * 915 mm

2/mm = 2.19 N/mm

1

Outer area equals 1715 mm2/mm

Outer Load equals 2394 n/m2 * 1715 mm

2/mm = 4.11 N/mm

1


The magnitude of the load acting on the substructure can be calculated as follows:


2

Area equals 2,090,000 mm2

Load equals 1915 n/m2 * 2,090,000 mm

2 = 4,009 N per pile

It is tentatively assumed that no sheltering occurs due to the piles. Therefore the wind load on the substructure is assumed to act on all the piles of the platform as can be seen in Figure 3-23.

Figure 3-23 schematisation of wind load north south

3.2.10 Live load parking area 50 LBS per square foot

On the parking area of the platform an additional live load of 50 LBS/ft2 is projected similar to the live load

projected on the trestle. A load of 50 LBS/ft2 corresponds with a load of 2.39 kN/m

2. This load is added to

the model as a uniform distributed load. Since the roadway of the parking area is not a part of the model, this load has to be added to the stringers supporting the roadway, as shown in Figure 3-24. The distance between the stringers is 3.00 m. The load on the stringers is therefore 2.39 kN/m

2 * 3m * 0.5 = 3.55 kN/m

1.

In Figure 3-24 the load on the middle stringers is shown in green. Here a double loads acts on the stringers since the concrete parking area extends on two sides of the stringer. The load in this case is 7.1 kN/m

1.


Figure 3-24 schematisation of live load on parking area and roadway

3.2.11 Wave forces extreme condition

The platform is located more or less perpendicular to the harbour entrance. It is therefore assumed that waves encounter the trestle at a 90° (perpendicular) angle. This also holds for the platforms. Based on [202] an extreme wave height (Hs) just in front of platform A of 1.23 m is to be expected. This is smaller than the wave height indicated in [304]. In front of platform B an extreme wave height (Hs) of 1.84 is to be expected. With a depth at the platform of 9 m and a wave period of 10 s the wave load on the piles can be calculated. This is done using RFWAVE and RF force. RFWAVE uses the Hmax which is equal to 1.8 times the Hs. Since the piles have two dimensions, 406 mm for the first 5.5 m and 610 mm for the part above that (with collar) two different runs of RF Force have been done (APPENDIX F). The applied wave load on the piles is combined using the wave load on the 406 mm pile for the first 5.5 m and the wave load on the wider section on the upper part. This leads to the following load distribution on the piles of platform A, see Table 3-11:

Level Total Force

Mm KN/m

-9000 0.29

-2500 0.38

2500 0.64

460 0.99

Table 3-11 Wave forces Platform A extreme condition, hmax = 2.21 m

And the load distribution as shown in Table 3-11 for the wave loads on the piles of platform B:


Level Total Force

Mm KN/m

-9000 0.60

-2500 0.86

2500 1.38

460 2.51

Table 3-12 Wave forces Platform B extreme condition, hmax = 3.32 m

The same force is applied on all the platform piles, including the batter piles. The batter piles have a longer shaft length but because the applied force acts over a specified length the force is equal in size as on the vertical piles. The piles of the parking area are assumed to be sheltered by the platform piles. In Figure 3-25 the schematisation of the wave load in the model is shown. The wave forces are acting in the negative X direction.

Figure 3-25 Schematisation of wave load on platform

3.2.12 Wave forces normal condition (Xdir)

In the normal case a wave height just in front of platform A of 0.67 m (HS) is assumed, [203]. This is similar to the wave height indicated in [304]. In front of platform B a wave height of 1.01 m is obtained. With a depth at the platform of 9 m and a wave period of 10 s the wave load on the piles can be calculated. This is done using RFWAVE and RF force [APPENDIX F]. RFWAVE uses the Hmax which is equal to 1.8 times the Hs. Since the piles have two dimensions, 406 mm for the first 3.5 m and 610 mm for the part above that (with collar) two different runs of RF Force have been done (APPENDIX F). The applied wave load on the piles is combined using the wave load on the 406 mm pile for the first 3.5 m and the wave load on the wider section on the upper part. This leads to the following load distribution on the pile, see Table 3-13


Level Total Force

Mm KN/m

-9000 0.11

-2500 0.14

2500 0.27

460 0.33

Table 3-13 Wave forces Platform A normal condition, hmax = 1.21 m

And the following load distribution for the piles of platform B, see Table 3-14

Level Total Force

Mm KN/m

-9000 0.21

-2500 0.27

2500 0.48

460 0.67

Table 3-14 Wave forces Platform B normal condition, hmax = 1.82 m

The same force is applied on all the platform piles, including the batter piles. The batter piles have a longer shaft length but because the applied force acts over a specified length the force is equal in size as on the vertical piles. The piles of the parking area are assumed to be sheltered by the platform piles.

3.2.13 Loading arms dead weight

The loading arms on the platforms are not part of the models and are therefore modelled as loads. the loading arms on platform A will remain intact, whereas the loading arms on platform B will be renewed. In the following sections the modelling of the loading arms for both platforms is discussed. Platform A The loading arms on platform A are placed upon a steel structure which is supported by the concrete deck. This structure is not in the model; therefore the forces of the loading arm acting upon the steel superstructure will have to be tranversed to the supports. This is done schematising the structure as portal frame with the loading arm on top of it, see APPENDIX D. The load of the wind force and the dead load are translated into support reactions that counteract the loads. These support loads will be entered in the model as the loading arm loads in the opposite reactions. This leads to the following loads, Table 3-15. In APPENDIX D the base load diagram is shown for the existing loading arms.

LOAD FORCE [kN] R1,V R1,H R2,V R2,H

Dead load (P) -145 75 kN 0 70 kN 0

Wind load (Fv) 24 -102.4 kN -10 kN 102.4 -14

Table 3-15 Reaction loads loading arms platform A

Platform B The loading arms for platform B are placed directly onto the concrete deck. They are also schematized as a dead weight load. The dead weight acts not in the centre line of the arm; therefore the dead weight exerts both a force on the underlying concrete plate as well as a moment. In APPENDIX D a schematisation of the loading arms can be found, the dead weight load is summarised in the table below, Table 3-16


LOAD TYPE FORCE ARM MOMENT

Dead weight (P) - 389 kN 900 mm 350 kNm

Torque force (T+) - 175 kN 1000 mm 175 kNm

Torque force (T-) +175 kN 1000 mm 175 kNm

Table 3-16 Dead weight forces caused by loading arm

The moment created by the dead weight will be schematised as two torque loads at the edges of the foot plate. The moment arm of the torque forces is therefore equal to half the width of the foot plate, which is 2.0 m (the arm is 1.0 m). The size of the torque forces can be calculated by dividing the dead weight moment in two and again dividing by the arm (350 knm/2/1.0 m = 175 kN). The torque forces will be added to the model creating a moment in the longitudinal axis of the platform. Three loading arms will be placed on top of the platform. APPENDIX D shows the location of the loading arms on the platforms, the schematisation of the dead load and torque forces is shown in Figure 3-26.

Figure 3-26 schematisation of dead load of loading arms

3.2.14 Loading arms wind force

The wind force acting on the loading arms of platform B is also schematised as a force combined with a moment. The force acts in the horizontal direction. In this case it is assumed that the wind encounters the platform at a perpendicular angle coming from the west side. The force is schematised at the centre point of the loading arm. The wind force on the loading arms for platform A is already described in the previous section. In APPENDIX D a schematisation of the loading arms can be found, the wind load is summarised in the table below, Table 3-17



Wind force (Fv) 98 kN 10,450 mm 1024 kNm



Table 3-17 wind load forces caused by loading arm

The moment created by the dead weight will be schematised as two torque loads at the edges of the foot plate. The moment arm of the torque forces is therefore equal to half the width of the foot plate, which is 2.0 m (the arm is 1.0 m). The size of the torque forces can be calculated by dividing the wind force moment in two and again dividing by the arm (1024 knm/2/1.0 m = 512 kN). The torque forces will be added to the model creating a moment in the longitudinal axis of the platform, see Figure 3-27 for the schematisation of the loads. The forces are acting in the same direction as the extreme wind forces.

Figure 3-27 Schematisation of wind forces loading arm

3.2.15 Gangway tower dead weight

The gangway tower on the platform is not part of the model and schematized as a dead weight load. The dead weight acts not in the centre line of the tower; therefore the dead weight exerts both a force on the underlying concrete plate as well as a moment. In APPENDIX D a schematisation of the gangway tower can be found, the dead weight load is summarised in the table below, Table 3-18. The dead weight of the tower is assumed to be 185 kN. For the wind loads the same forces as for the loading arms is assumed.


Dead weight (P) - 185 kN 900 mm 167 kNm

Torque force (T+) - 84 kN 1000 mm 175 knm

Torque force (T-) +84 kN 1000 mm 175 knm

Table 3-18 Dead weight forces caused by gangway tower

The moment created by the dead weight will be schematised as two torque loads at the edges of the foot


plate. It is assumed that the loading tower has the same foot plate as the loading arms. The moment arm of the torque forces is therefore equal to half the width of the foot plate, which is 2.0 m (the arm is 1.0 m). The size of the torque forces can be calculated by dividing the dead weight moment in two and again dividing by the arm (167 knm/2/1.0 m = 84 kN). The torque forces will be added to the model creating a moment in the longitudinal axis of the platform. One gangway tower will be placed on top of the platform. The location of the gangway tower is shown in APPENDIX D; see Figure 3-28 for the schematisation of the dead load.

Figure 3-28 schematisation of dead load gangway tower

3.2.16 Gangway tower wind force

The wind force acting on the gangway tower is also schematised as a force combined with a moment. The force acts in the horizontal direction. In this case it is assumed that the wind encounters the platform at a perpendicular angle coming from the west side. The force is schematised at the centre point of the gangway tower. In APPENDIX D a schematisation of the gangway tower can be found, the wind load is summarised in the table below, Table 3-19


Wind force (Fv) 98 kN 10,450 mm 1024 kNm



Table 3-19 wind load forces caused by gangway tower

The moment created by the wind load will be schematised as two torque loads at the edges of the foot plate. The moment arm of the torque forces is therefore equal to half the width of the foot plate, which is 2.0 m (the arm is 1.0 m). The size of the torque forces can be calculated by dividing the wind force moment in two and again dividing by the arm (1024 knm/2/1.0 m = 512 kN). The torque forces will be added to the model creating a moment in the longitudinal axis of the platform, see Figure 3-29.


Figure 3-29 schematisation of wind load gangway tower

3.2.17 Uniform distributed load

To compensate for the absence in the model of the constructions on top of the concrete deck of the loading platform a uniform distributed load will be taken acting upon this deck. A load of 4 kN/m

2 is assumed.

3.2.18 Hawser pull

On top of the loading platform two bollards are situated. According to [304] on these bollards a hawser pull of 50 kips should be applied. 50 kips corresponds with a force of 222.4 kN. This force acts at the bollard in a direction that is not specified. It is assumed here that the force acts on one bollard in the positive Z direction as shown in Figure 3-30. Since there is a vertical distance between the point at which the line exerts its force on the bollard and the beam that the bollard eventually passes this load onto, a moment needs to be added to the model.

The elevation of the line bollard connection point above the substructure is estimated to be 500 mm.

The forces acting in the Z-direction = 222.4 kN.

The corresponding moment is 222.4 kN * 500 mm = 111.2 kNm

The width of the footplate in the direction perpendicular to the berthing face is 500 mm, the torque arm is 500/2 = 250 mm.

The corresponding torque force is 222.4 kN The torque forces will be added to the model at a distance of 250 mm on the berth side and the back side of the centre point of the bollard, see for the schematisation of the load.


Figure 3-30 Schematisation of bollard load

3.2.19 Breasting forces; ship impact load

Ships mooring at the platform can exert a breasting force at the platform due to ship impact. In [304] a ship impact force of 20 tons over a fender length of 10 foot is prescribed. This corresponds with a force of 196 kN over 3 m. In front of the loading platform a fender system is located. It is assumed that the indicated 196 kN ship impact force transverses through the fenders unto the platform as shown in APPENDIX G. The ship impact load is modelled on the platform as concentrated loads acting on the outer two pile caps of the platform as shown in Figure 3-31.


Figure 3-31 schematisation of ship impact load

3.2.20 Temperature load

As a result of temperature variation loads can occur within the construction. To model this load a temperature load is added to the model. In [304] temperature variations are stated to be between 35° F and 110° F. This corresponds to 274° K and 316 ° K. Since it is unclear whether the ambient temperature or the construction temperature is described here engineering practice is used to determine the temperature variations that can occur. The temperature load is added to the upper part of the model. The steel piles are mostly below water level and are therefore subjected to much smaller temperature fluctuations. Hence the temperature load is only added to the superstructure and pile caps of the platform model, see Figure 3-32. Assuming that the construction is build in winter (average temperature is 15°C) and heats up in summer (60°C) a positive temperature variation of 45° can occur Assuming that the construction is build in moderate temperatures (36°C) and cools down in winter (15°C) a negative temperature variation of 21° can occur.


Figure 3-32 Schematisation of temperature load

3.2.21 Seismic load

Similar tot the trestle seismic load is added to the platforms acting in three main directions, (X,Y and Z). The seismic calculation uses the weight loads to calculate the resulting seismic force on the structure. The weights used in this platform model are:

1. self weight of platform and parking area construction 2. self weight concrete roadway 3. self weight piping 4. self weight loading arms 5. self weight gangway tower 6. self weight concrete collar 7. self weight represented by UDL = 4 kN/m

2

With these parameters entered into the model, STAAD calculates a seismic load in both the X, Y and the Z direction. These loads are used in several load combinations to determine the residual strength of the Trestle.

3.2.22 Self weight concrete collar

As is already explained in section 2.1.1 the modelled cross section of the piles, in combination with the concrete collar neglects the dead weight difference. This difference in dead load is remedied in the model by acting a uniform distributed load of 0.61 kN/m. This load is added to the piles as shown in Figure 3-33.


Figure 3-33 Schematisation of self weight concrete collar on piles

3.2.23 Self weight omitted concrete deck

In section 2.2.4 already reference is made about the size of the concrete deck on the loading platform that is smaller in the model than in reality. To accommodate for the accompanying weight difference a uniform distributed load is added to the sides of the platform as shown in Figure 3-34. The magnitude of the forces to be added to the platform is determined as follows. Volume of concrete is calculated by the overhang (0.15 and 0.40m) multiplied by the thickness of the concrete. Assumed is 250 mm + 165 since concrete curbs run along the edges of the platform. The concrete weight is assumed to be 24.5 kN/m In total this leads the following loads:

- berth edge and backside: 0.40 * 0.415 * 24.5 = 4.07 kN/m - sides: 0.15 * 0.415 * 24.5 = 1.53 kN/m


Figure 3-34 Schematisation of dead load omitted part of the concrete deck

3.2.24 Seismic moment loading arms

The loading arms are not part of the model but are schematised as loads acting on the concrete deck. Since the mass of the loading arms is concentrated at a certain height above the platform in case of seismic motion an additional moment has to be modelled. According to APPENDIX X, the force and arm of the seismic motion of the loading arms on platform B are as follows:

- Fsh = 99.25 kN, arm As = 9650 mm - Fsv = 66.30 kN, arm B = 900mm

From these forces and arms two moments can be derived:

- Msh = 957.76 kNm - Msv = 59.67 kNm

The horizontal moment is assumed to act in both X and Z direction occurring simultaneously with seismic forces in the corresponding direction. The vertical moment is assumed to act simultaneously with vertical seismic forces and has an orientation along the X axis. Figure 3-35 shows a schematisation of the seismic forces acting in the Z direction. For platform A no such values are obtained. Therefore this mechanism is ignored.


Figure 3-35 schematisation of seismic forces loading arms on platform A

3.2.25 Vehicle loading

Vehicle loading is assumed according to BS 5400. A nominal HB loading is analysed to be acting on different parts of the trestle. The shortest wheelbase is assumed to give the most severe effect. Analyses showed that the vehicle load had the greatest effect on pressure and tension in the platform piles as shown in the following figures. Vehicle loading located as shown in Figure 3-36 leads to the highest tension forces in the piles of the platform whereas vehicle loading as shown in Figure 3-37 leads to the highest compression forces in the platform piles.


Figure 3-36 Schematisation of vehicle loading for maximum tension

Figure 3-37 schematisation of vehicle loading for maximum pressure


4 Load combinations

The STAAD models will be tested for 5 basic loading combinations. The loading cases are assembled according to [106], and consist of a normal case, extreme metocean case, extreme mooring case, extreme berthing case and a Seismic case. Since no mooring facilities exist in the vicinity of the trestle, in the mooring case only the anchor force can be applied to this model. The loading combinations are chosen in such a way as to maximise the pressure and tension in the piles. In directional cases, pressure is maximised by adding live loads and applying a load factor of 1.2 for dead loads and tension is maximised by omitting live loads and applying a load factor of 0.9 for dead loads. The seismic cases are determined according to UBC 1997 [103]. The UBC states that In the case of both horizontal and vertical components, the horizontal components should alternatively be multiplied by 0.3 while the other components are multiplied by 1. For the 105 cases the X direction is assumed normative and the Z component is multiplied by 0.3, whereas the 107 cases assume the Z direction normative and multiply the X direction by 0.3. Within these cases the directions are alternatively varied. The cases with a negative direction for the Z component are optimised for tension by multiplying the dead load factors by 0.9. Special attention is given to the piles of the loading platforms. The following cases were defined:

101 Load combination normal condition;

1011 normal condition with positive temperature difference (+45°K)

1012 Normal condition with negative temperature difference (-20°)

102 Load combination extreme metocean

1021 Extreme metocean with live loads applied

1022 Extreme metocean without live loads

103 Load combination extreme mooring

1031 mooring with live loads applied

1032 mooring without live loads applied

104 Load combination extreme berthing 1

1041 berthing with live loads applied

1042 berthing without live loads applied

105 Load combination seismic

8 load combinations have been derived for the seismic loads, alternating positive and

negative directions. X is the predominant direction.

107 Load combination seismic

8 load combinations have been derived for the seismic load, alternating positive and

negative directions. Z is the predominant direction.

In Figure 4-1 and Figure 4-2 overviews are given of all the determined load cases.

1 Berthing load is only applied on the platform models


Figure 4-1 Load combinations ULS


Figure 4-2 Load combinations SLS


5 Results

In this section the results of the STAAD models are discussed. For the loading platform focus of the discussion is on the normal forces in the piles. Tabulation of the results can be found in the appendices. All the steel members are checked according tot the British Standard 5950 [105]. The indicated steel grade is A36 with a yield-strength of 248 kN/m

2.

5.1 TRESTLE

5.1.1 Design results

In APPENDIX O a table of the design results of the STAAD model can be found. STAAD checks the beams according to BS 5950. This table shows that for three members, the piles of bents 3 and 4, the loads exceed the capacity according to BS 5950. The cause of this failure can be found in the modelling of the expansion joints as releases. In Figure 5-1 can be seen that the section of the trestle of which the failed member is a part is placed between two releases and contains no transverse fortification in the form of batter piles. The section on itself is therefore not strong enough to take the load.

Figure 5-1 Deflection of trestle bents 3 and 4

In reality however, the surrounding structure will take part of the load once the deflection reaches the limit of the expansion joint (30 mm). To observe the effect of the divided load a separate STAAD model is constructed of the whole trestle where the releases on one end of the section are fixed in the X direction. The section no longer acts as an individual part and the construction is able to withstand the load according to BS 5950, see Figure 5-2:


Figure 5-2 Deflection of trestle bents 3 and 4 with X fixed

5.1.2 Beam end forces summary

In Table 5-1 an example is given of a STAAD output table. The table shows the highest occurring forces in the piles belonging to the trestle. From this table three maximum load situations are obtained that are checked using a calculation sheet based on BS 5950. These three loadings correspond with the highest compression force, the highest combined bending moment (Y and Z) and the highest eccentricity (moment divided by force). In Table 5-1 the case of the highest compression force is 1125 kN, the highest bending moment (Mb) = 169 kNm and the highest eccentricity is 1.42 m. The members where these maximums occur are checked for the load case in which they occur using the calculation sheet. The shear and bending results of these beams can be found in appendix M and the calculation sheets in appendix N. The check proves that the strength of the beams is sufficient to bear the load. The maximum compression force occurs at beam 3312, This load exceeds the geotechnical limit for the piles (80 tons max). Since it is a seismic combination that leads to this load, the next occurring highest compression and tension loads are analysed for non seismic combinations. In APPENDIX L, forces summaries are shown for the different pile sets and the different load combinations under operational conditions. These tables show that, aside from the seismic load combinations, pressure and tension forces in the trestle piles remain within geotechnical limits, of 80 tons of compression and 40 tons of tension.


Beam L/C Node Fx kN Fy kN Fz kN My kNm Mz kNm

Mb kNm

Mb/FX m

Max Fx 3312 1075 3327 1125.03 -2.98 1.35 7.05 0.41 7.06 0.01

Min Fx 1319 1057 1337 -851.35 -10.09 -0.16 -0.07 -5.83 5.83 -0.01

Max Fy 3501 1054 3501 1036.50 59.33 7.98 -14.77 71.64 73.15 0.07

Min Fy 3501 1056 3501 -392.58 -54.35 -8.27 15.54 -65.28 67.10 -0.17

Max Fz 306 1071 307 292.52 22.97 44.80 57.29 -22.34 61.49 0.21

Min Fz 301 1072 301 117.29 14.91 -39.37 162.63 37.51 166.90 1.42

Max Mx 407 1074 409 219.20 -3.59 10.78 -72.68 -13.17 73.87 0.34

Min Mx 204 1076 209 -271.42 9.37 -23.60 96.91 26.85 100.56 -0.37

Max My 301 1076 301 117.56 9.60 -38.49 165.48 8.31 165.68 1.41

Min My 301 1074 301 359.21 -14.74 43.01 -167.49 -26.48 169.57 0.47

Max Mz 201 1054 201 447.88 19.49 9.47 -37.31 83.49 91.45 0.20

Min Mz 106 1011 108 209.00 20.33 7.70 -0.84 -95.53 95.53 0.46

Table 5-1 Beam end summary Trestle ULS


5.1.3 Maximum compression per pile

In Table 5-2 the maximum forces acting on each individual pile are shown. The table shows both the maximum occurring force in each pile as well as the minimum occurring force. For both the load combination resulting in the force is given as well. In the first column of the table the actual pile number is given, the second column denotes the beam number in STAAD. All values are derived from SLS cases. Positive values indicate compression forces, negative values indicate tension.

Pile # Beam # Maximum force Load combination

for max force Minimum force

Load combination for min force

1-A 101 275.74 1055 163.3 1052

1-B 106 228.331 1071 110.029 1077

2-A-2 201 707.572 1071 -176.673 1077

2-A-1 204 459.027 1078 -393.557 1072

2-B-1 207 1074.81 1055 -792.83 1053

2-B-2 212 1062.492 1054 30.731 1072

3-A 301 323.991 1078 117.286 1072

3-B 306 268.862 1071 70.081 1077

4-A-2 401 600.061 1071 -145.983 1077

4-B 406 282.048 1011 121.996 1077

4-A-1 407 376.266 1078 -338.168 1072

5-A-2 501 693.057 1071 -181.909 1077

5-B 506 505.466 1011 148.007 1057

5-A-1 507 444.887 1078 -401.608 1072

6-A 601 296.031 1055 179.697 1053

6-B 606 248.146 1075 132.397 1073

7-A-2 701 374.103 1078 -184.033 1072

7-B-1 706 385.686 1071 31.426 1074

7-A-1 707 253.808 1011 -137.584 1072

7-B-3 712 222.357 1071 -0.304 1056

7-A-5 713 316.669 1075 -231.919 1073

7-A-6 718 352.474 1054 17.589 1011

7-A-3 719 390.752 1055 -276.171 1053

7-A-4 724 410.027 1054 8.274 1072

7-B-2 725 611.412 1055 -471.008 1053

7-B-4 730 551.355 1054 33.866 1011

8-A-2 801 468.523 1071 -49.792 1077

8-B 806 247.445 1054 132.271 1056

8-A-1 807 296.738 1078 -190.772 1072

9-A-2 901 657.759 1071 -117.359 1077

9-B 906 266.747 1075 151.555 1073

9-A-1 907 365.3 1078 -351.281 1072

10-A-2 1001 694.032 1071 -274.029 1077

10-B 1006 200.681 1071 106.111 1077

10-A-1 1007 504.236 1078 -457.798 1072

11-A 1101 335.313 1078 195.277 1072

11-B 1106 294.291 1071 153.157 1077

12-A 1201 298.507 1055 176.891 1053

12-B 1206 249.141 1071 111.443 1077

13-C 1311 433.057 1011 219.759 1052

13-A-1 1314 951.503 1058 -831.701 1052

13-B-2 1319 963.71 1051 1.522 1042

13-B-3 1320 822.349 1078 -710.753 1072

13-B-1 1325 747.373 1055 2.441 1077

13-A-3 1326 922.591 1054 -676.758 1056


13-A-2 1331 900.574 1071 12.649 1011

14-A 1401 303.275 1078 182.185 1072

14-B 1406 247.706 1054 121.969 1056

15-A 1501 334.361 1058 210.071 1052

15-B 1506 291.245 1051 164.729 1057

16-A-2 1601 759.395 1054 -311.387 1056

16-B 1606 199.834 1075 114.544 1073

16-A-1 1607 548.613 1055 -498.939 1053

17-A-2 1701 913.682 1054 -370.431 1056

17-B 1706 265.205 1074 158.034 1076

17-A-1 1707 647.697 1055 -605.599 1053

18-A 1801 305.776 1058 191.547 1052

18-B 1806 257.466 1054 139.261 1056

19-A 1901 312.747 1075 185.361 1073

19-B 1906 261.328 1071 135.949 1077

20-A-2 2001 652.745 1021 -394.139 1053

20-B-1 2006 560.113 1054 5.549 1071

20-A-1 2007 401.828 1021 -272.315 1053

20-A-3 2012 369.335 1054 3.644 1078

20-A-6 2013 505.192 1074 -393.377 1076

20-A-5 2018 509.191 1071 12.733 1011

20-A-4 2019 547.658 1074 -411.303 1076

20-A-3 2024 548.43 1071 -2.733 1022

20-B-2 2025 758.109 1078 -599.76 1072

20-B-4 2030 751.208 1075 24.013 1057

21-A 2101 306.92 1078 182.191 1072

21-B 2106 253.404 1074 130.966 1076

22-A 2201 328.272 1055 211.005 1053

22-B 2206 284.236 1051 163.468 1057

23-A-2 2301 500.547 1051 -159.835 1057

23-B-1 2306 439.096 1058 3.719 1072

23-A-1 2307 405.287 1058 -244.348 1052

23-B-2 2312 382.923 1051 6.258 1078

24-A-2 2401 578.53 1051 -163.679 1057

24-B-1 2406 522.608 1055 25.061 1073

24-A-1 2407 447.36 1058 -275.236 1052

24-B-1 2412 427.838 1054 -4.332 1075

25-A 2501 308.721 1058 195.972 1052

25-B 2506 258.34 1054 145.488 1056

26-A 2601 296.682 1075 172.365 1073

26-B 2606 244.785 1071 114.83 1077

27-A-1 2701 749.714 1021 -561.471 1052

27-B-2 2706 703.477 1051 3.742 1012

27-B-3 2707 909.662 1078 -719.971 1072

27-B-1 2712 884.024 1075 6.331 1051

27-A-3 2713 875.768 1074 -635.699 1076

27-A-2 2718 859.615 1071 9.636 1055

28-A 2801 240.376 1058 143.487 1052

28-B-2 2806 88.326 1054 41.158 1056

28-B-1 2807 284.4 1078 158.423 1072

29-A 2901 229.001 1055 135.31 1053

29-B 2906 357.971 1051 219.055 1057

30-A-2 3001 356.699 1054 -229.476 1022

30-B-2 3006 482.042 1022 26.165 1073

30-A-1 3007 413.075 1021 -181.188 1053

30-B-1 3012 399.477 1054 2.46 1076

31-A-2 3101 360.973 1051 -219.461 1022


31-B-1 3106 532.315 1022 5.934 1054

31-A-1 3107 422.261 1021 -170.516 1052

31-B-2 3112 434.504 1051 2.768 1077

32-A 3201 212.275 1055 131.009 1053

32-B 3206 321.186 1071 181.432 1077

33-A-1 3301 733.891 1021 -614.348 1053

33-A-2 3306 810.263 1054 10.805 1075

33-B-1 3307 1097.127 1074 -779.737 1076

33-B-2 3312 1095.787 1075 25.492 1058

34-A 3401 215.495 1058 125.827 1052

34-B 3406 323.276 1074 179.132 1076

35-B 3501 997.156 1054 -392.582 1056

36-A-2 3601 711.774 1054 -389.546 1022

36-B 3606 251.045 1074 162.561 1076

36-A-1 3607 608.054 1021 -521.212 1053

37-A 3701 230.771 1055 132.427 1053

37-B 3706 368.229 1054 216.684 1056

38-A 3801 218.85 1055 124.728 1053

37-B 3806 314.556 1071 185.635 1021

39-A-1 3901 827.207 1021 -548.199 1053

39-B-2 3906 668.058 1054 27.119 1012

39-A-5 3907 424.005 1074 -328.459 1076

39-A-4 3912 420.977 1071 12.266 1042

39-A-3 3913 453.58 1074 -299.031 1076

39-A-2 3918 451.637 1071 36.464 1021

39-B-3 3919 757.377 1078 -504.066 1072

39-B-1 3924 731.975 1075 19.364 1051

40-A 4001 219.601 1058 123.97 1052

40-B 4006 314.102 1074 185.952 1076

41-A 4101 232.803 1058 130.998 1052

41-B 4106 368.384 1051 216.438 1057

42-A-2 4201 659.927 1051 -341.507 1022

42-B 4206 253.01 1051 162.439 1057

42-A-1 4207 553.845 1021 -466.701 1052

43-A-2 4301 664.397 1051 -318.391 1022

43-B 4306 344.433 1054 221.869 1056

43-A-1 4307 549.82 1021 -448.549 1052

44-A 4401 236.157 1075 149.548 1073

44-B-2 4406 84.018 1051 47.727 1057

44-B-1 4407 283.794 1075 168.558 1073

45-A-1 4501 382.548 1021 -167.63 1053

45-B-1 4506 296.978 1054 0.237 1077

45-B-3 4507 346.029 1078 -231.221 1072

45-B-2 4512 395.16 1075 18.784 1011

45-A-3 4513 360.017 1074 -206.722 1076

45-A-2 4518 432.337 1071 -4.557 1055

Table 5-2 forces on trestle piles (SLS)


5.1.4 Reduced pile wall thickness

Under water inspections showed that the pile wall thickness was reduced due to corrosion. The largest reduction in wall thickness occurred around the splash zone. it is indicated for the trestle piles that the reduction around the splash zone is 40%, above and below the splash zone the reduction is 5%. It is assumed that the splash zone corresponds with the concrete covered part of the piles. In the model, therefore this part of the pile is modelled with a 40 % reduced pile wall thickness. The rest of the pile is modelled with a 5% reduction. The corresponding outer pile diameters are as follows:

around splash zone: outer diameter is 399 mm;

above and below splash zone: outer pile diameter is 405 mm; The STAAD beam end forces table is shown in Appendix T as well as the unity checks for the members under highest compression, highest total moment and highest eccentricity (see section 5.1.2). The beam end forces table gives the highest occurring forces for all load combinations (including seismic). The unity checks show that the loads exceed the capacity of all checked piles. When only non-seismic cases are checked only the highest compression force leads to a unity check of more than one. The buckling results are computed assuming the reduced wall thickness over the total length of the pile instead of around the splash zone. This leads to a conservative assessment of buckling.


5.2 LOADING PLATFORM A


In Table 5-3 an example is given of a STAAD output table. The table shows the highest occurring forces in the piles belonging to platform A including the parking area. From this table three maximum load situations are obtained that are checked using a calculation sheet based on BS 5950. These three loadings correspond with the highest compression force, the highest combined bending moment (Y and Z) and the highest eccentricity (moment divided by force). In the case of Table 5-3 the highest compression force is 1943 kN, the highest bending moment (Mb) = 72.29 kNm and the highest eccentricity is 0.21 m. The members where these maximums occur are checked for the load case in which they occur using the calculation sheet. The shear and bending results of these beams can be found in appendix M and the calculation sheets in appendix N. The check proves that the strength of the beams is sufficient to bear the load except for the maximum compression force. This force has a magnitude of 1943 kN, which is far beyond the geotechnical limit of 800 kN and also leads to failure in the pile. The maximum compression force occurs at beam 4707, which is one of the parking area piles and is mainly the result of the 500 LBS/ft

2 truck/ live load. This load exceeds the geotechnical limit for the piles

(80 tons max). It is therefore advised to check the occurrence of this live load and the geotechnical capacity of the piles. In APPENDIX L, forces summaries are shown for the different pile sets and the different load combinations under operational conditions. These tables show that, aside from the seismic load combinations, pressure and tension forces in the platform piles remain within geotechnical limits.


Mb kNm

Mb/FX m

Max Fx 4707 1012 4725 1943.29 0.43 2.72 -12.86 6.47 14.39 0.01

Min Fx 4607 1072 4622 -869.06 12.82 1.00 -0.24 -26.87 26.87 -0.03

Max Fy 4607 1071 4621 -852.45 16.18 0.94 -6.54 72.00 72.29 -0.08

Min Fy 4607 1077 4622 898.67 -9.35 -1.17 0.73 12.92 12.94 0.01

Max Fz 4601 1077 4601 -690.67 -1.06 11.81 -57.25 -8.49 57.87 -0.08

Min Fz 4601 1071 4601 1066.09 0.86 -12.49 62.27 6.28 62.58 0.06

Max Mx 4607 1072 4621 -864.54 14.33 1.00 -7.09 66.13 66.50 -0.08

Min Mx 4607 1011 4621 112.25 2.76 -1.77 23.36 6.07 24.13 0.21

Max My 4601 1071 4601 1066.09 0.86 -12.49 62.27 6.28 62.58 0.06

Min My 4601 1077 4601 -690.67 -1.06 11.81 -57.25 -8.49 57.87 -0.08

Max Mz 4607 1071 4621 -852.45 16.18 0.94 -6.54 72.00 72.29 -0.08

Min Mz 7419 1051 7442 -552.52 8.22 -1.22 -4.62 -46.30 46.53 -0.08

Table 5-3 Beam end summary platform A ULS



In Table 5-4 the maximum forces acting on each individual pile are shown. In the final column of the table the load combination resulting in the pile force is shown. All values are derived from SLS cases. Positive values indicate compression forces, negative values indicate tension. The Table only shows platform piles

Pile # Beam # Max force Load combination

C1 741 596.649 1058 LOAD CASE SEISMIC 58

A1 7001 100.091 1075 LOAD CASE SEISMIC 75

E1 7006 183.275 1051 LOAD CASE SEISMIC 51

B1 7007 479.145 1051 LOAD CASE SEISMIC 51


D1 7013 198.746 1074 LOAD CASE SEISMIC 74


E2 7106 304.358 1021 LOAD CASE EXTREME METOCEAN +LL SLS





E5 7206 391.921 1021 LOAD CASE EXTREME METOCEAN +LL SLS

















C5-1 7601 986.767 1074 LOAD CASE SEISMIC 74




Table 5-4 maximum force for each pile (SLS)


5.2.3 Minimum compression/ tension per pile

In Table 5-5 the maximum forces acting on each individual pile are shown. In the final column of the table the load combination resulting in the pile force is shown. All values are derived from SLS cases. Positive values indicate compression forces, negative values indicate tension. The Table only shows platform piles.


C1 741 -45.889 1073 LOAD CASE SEISMIC 73



B1 7007 59.7 1022 LOAD CASE EXTREME METOCEAN -LL SLS












D5 7213 -13.906 1022 LOAD CASE EXTREME METOCEAN -LL SLS





D6 7313 -524.972 1053 LOAD CASE SEISMIC 53

A3 7401 -524.972 1053 LOAD CASE SEISMIC 53


B3 7407 -487.609 1053 LOAD CASE SEISMIC 53




E3 7419 -414.133 1054 LOAD CASE SEISMIC 54


C5-1 7601 -761.607 1076 LOAD CASE SEISMIC 76

C5-2 7606 22.214 1042 LOAD CASE EXTREME BERTHING -LL SLS


C6-2 7712 12.149 1042 LOAD CASE EXTREME BERTHING -LL SLS

Table 5-5 minimum force for each pile (SLS)

The STAAD output for the model of loading platform A can be found in APPENDIX I. In this section the forces acting on the piles is discussed.



According to the model all the members have sufficient capacity to bear the applied load except for beam 4707. The loading of this beam is already described in the previous section. The geotechnical limit of the piles is exceeded for seismic cases only.




above and below splash zone: outer pile diameter is 404 mm; The STAAD beam end forces table is shown in Appendix R as well as the unity checks for the members under highest compression, highest total moment and highest eccentricity (see section 5.2.1). The beam end forces table gives the highest occurring forces for all load combinations (including seismic). The unity checks show that the loads exceed the capacity of only the pile under highest compression. When only non-seismic cases are checked the highest compression force also leads to a unity check of more than one since it is a non seismic case that leads to this load. The buckling results are computed assuming the reduced wall thickness over the total length of the pile instead of around the splash zone. This leads to a conservative assessment of buckling.


5.3 LOADING PLATFORM B


In Table 5-6 an example is given of a STAAD output table. The table shows the highest occurring forces in the piles belonging to platform B including the parking area. From this table three maximum load situations are obtained that are checked using a calculation sheet based on BS 5950. These three loadings correspond with the highest compression force, the highest combined bending moment (Y and Z) and the highest eccentricity (moment divided by force). In the case of Table 5-6 the highest compression force is 1182 kN, the highest bending moment (Mb) = 57.04 kNm and the highest eccentricity is 0.20. The members where these maximums occur are checked for the load case in which they occur using the calculation sheet. The shear and bending results of these beams can be found in appendix J and the calculation sheets in appendix K. The check proves that the strength of the beams is sufficient to bear the load. The maximum compression force occurs at beam 5007, which is one of the parking area piles and is mainly the result of the 500 LBS/ft

2 truck/ live load. This load exceeds the geotechnical limit for the piles

(80 tons max). It is therefore advised to check the occurrence of this live load and the geotechnical capacity of the piles. In APPENDIX I, forces summaries are shown for the different pile sets and the different load combinations under operational conditions. These tables show that, aside from the seismic load combinations, pressure and tension forces in the platform piles remain within geotechnical limits.


Mb kNm

Mb/FX m

Max Fx 5007 1012 5025 1182.41 2.33 -0.13 -0.07 15.87 15.87 0.01

Min Fx 9601 1076 9602 -849.46 1.87 -0.66 -3.59 -15.30 15.71 -0.02

Max Fy 4907 1075 4921 -651.98 12.68 -1.13 4.89 57.04 57.25 -0.09

Min Fy 9013 1021 9041 329.76 -7.08 -0.01 0.00 -36.98 36.98 0.11

Max Fz 4901 1074 4901 -435.65 0.05 8.77 -44.10 -1.65 44.13 -0.10

Min Fz 4901 1076 4901 794.78 -0.84 -8.65 45.80 -3.45 45.93 0.06

Max Mx 4907 1071 4921 -645.50 12.61 0.75 -7.09 56.67 57.11 -0.09

Min Mx 4907 1077 4921 690.99 -4.67 -1.88 13.51 -32.49 35.18 0.05

Max My 5006 1071 5008 283.92 0.73 8.44 51.87 -4.65 52.08 0.18

Min My 5001 1078 5001 225.33 0.55 7.47 -46.07 -0.73 46.07 0.20

Max Mz 4907 1075 4921 -651.98 12.68 -1.13 4.89 57.04 57.25 -0.09

Min Mz 9410 1021 9426 -194.55 1.71 -0.43 -2.79 -39.87 39.96 -0.21

Table 5-6 Beam end summary platform B ULS



In Table 5-7 the maximum forces acting on each individual pile are shown. In the final column of the table the load combination resulting in the pile force is shown. All values are derived from SLS cases. Positive values indicate compression forces, negative values indicate tension. The table shows only the platform piles.










B2 9107 393.704 1021 LOAD CASE EXTREME METOCEAN +LL SLS

C3 9110 586.222 1021 LOAD CASE EXTREME METOCEAN +LL SLS
























Table 5-7 maximum force for each pile (SLS)


5.3.3 Minimum compression/ tension per pile

In Table 5-8 the maximum forces acting on each individual pile are shown. In the final column of the table the load combination resulting in the pile force is shown. All values are derived from SLS cases. Positive values indicate compression forces, negative values indicate tension. The table shows only the platform piles.













A5 9201 78.867 1022 LOAD CASE EXTREME METOCEAN -LL SLS




D5 9213 9.94 1022 LOAD CASE EXTREME METOCEAN -LL SLS

















C6-2 9712 77.292 1031 LOAD CASE EXTREME MOORING +LL SLS

Table 5-8 minimum force for each pile (SLS)



According to the model all the members have sufficient capacity to bear the applied load. The geotechnical limit of the piles is exceeded for seismic cases only.




above and below splash zone: outer pile diameter is 404 mm; The STAAD beam end forces table is shown in Appendix S as well as the unity checks for the members under highest compression, highest total moment and highest eccentricity (see section 5.3.2). The beam end forces table gives the highest occurring forces for all load combinations (including seismic). The unity checks show that the loads exceed the capacity of only the pile under highest compression. When only non-seismic cases are checked the highest compression force also leads to a unity check of more than one since it is a non seismic case that leads to this load. The buckling results are computed assuming the reduced wall thickness over the total length of the pile instead of around the splash zone. This leads to a conservative assessment of buckling.


6 References

6.1 Reports

General reports

[101] Pile design and construction practice, 4th edition, M.J.Tomlinson

[102] AASHTO standard specifications for highway bridges, 1996

[103] UBC 1997 uniform building code, volume 2, structural engineering design provisions, international conference of building officials

[104] Pipe sections

[105] British Standard 5950-1:2000, structural use of steelwork in building, part 1: code of practice for design- rolled and welded sections, 2000

[106] Design of jetty facilities, design and engineering practice, 35.00.10.10-Gen, XXXX, February 2007

DMC reports

[201] 952200-rap-u-0017: structural analysis existing and future Dolphins, July 17 2008

[202] 952200-rap-u-0004, Marsa Al Brega terminal - upgrading study; Overview required structural provisions, revision B, 4 April 2007

[203] 952200-rap-u-0001, Determination of wind and wave climate at Port Entrance, revision B, November 2005

6.2 Drawings

[301] TC 3057/B – SS1 – 3 – 73: XXXX, LNG jetty renovations pipe repair details, 17-05-85

[302] TC 3057/B – SS1 – 3 – 74: XXXX, LNG jetty renovation, Trestle framing plan, 17-05-85

[303] UNKNOWN - SS1 – 3 – 13: XXXX, LNG pier repair, date unknown;

[304] 335 – SS1 – 3 – C1– 0100: XXXX Harbor extension Location plan, July 15 1966

[305] TC 3057/B – SS1– 3– 94: XXXX, LNG jetty renovation plan and framing loading platform – berth A;

[306] TC 3057/B – SS1– 3– 78: XXXX, LNG jetty renovation, Trestle framing details sheet 2 of 2, may 17 1985;

[307] TC 3057/ B – SS1– 3– 75: XXXX, LNG jetty renovation Trestle pile caps, May 7 1985


Enclosures

APPENDIX A.pdf

appendix K.pdf

APPENDIX B.pdf

appendix L.pdf

APPENDIX C.pdf

appendix M.pdf

APPENDIX D.pdf

appendix N.pdf

APPENDIX E.pdf

appendix O.pdf

APPENDIX F.pdf

appendix P.pdf

APPENDIX G.pdf

appendix Q.pdf

APPENDIX H.pdf

appendix R.pdf

appendix I.pdf

appendix S.pdf

appendix J.pdf

appendix T.pdf

s trestle and loading platforms

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