PTQ Q4 2022 Issue

shown by the top red arrow. As a result, the rear saddle supported by W1 restrains the motion, while the front saddles supported by walls W2 to W4 allow the vessel to slide. The thrust forces on the rear support ‘A’ could be sig- nificant to result in using a massive concrete wall size. Note that the vessel load distribution depends upon the number of saddle walls used in the support system. Figure 5 shows the concrete support system used for INTS. Concrete walls W1-W4 support the horizontal ves - sel, as shown by hatched rectangles. Column supports frames F2 and F3 are shown by hatched squares. Pile- caps F1, F2 and F3 also support saddle walls. Pile-cap F1 has trapezoidal geometry and is supported by three piles. During the design phase, it was found that this geometry is very effective to use at this location. Concrete wall W1 is projected from F1 and contains the fixed vessel saddle. Note that the F1 model is not supporting any platform col - umn. Pile-cap F2 supports walls W2 and W3 that contains a sliding saddles and two platform column pedestals along gridlines A-5 and B-5. Note that the pedestals shown by the narrow, hatched rectangles support the platform col- umns. Pile-cap F2 supports concrete walls W2 and W3. Pile-cap F3 supports concrete wall W4 that contain slid- ing saddle and two column pedestals along gridlines A-6 and B-6. Twelve isolated pile supports are denoted by F4. Circular pedestals are projected from the piles directly to support isolated platform columns. Note that an identical concrete pedestal size is used for all platform columns. Base plates of the columns are shown in blue and anchored to the pile head using four anchor rods. Teflon

coatings are used on the sliding side with a low coefficient of friction to reduce the induced forces during operation. It is also recommended to reinforce the saddle plate using equally spaced vertical stiffeners on both sides. Finite element models were developed to simulate the load transfer from the saddle base plates to the concrete caps. The calculated saddle reactions were applied at the top of the walls. Pile-caps F1 to F3 were modelled using 2D plate elements. The attached concrete walls were also modelled in the perpendicular direction using 2D elements. Compatibility of displacements and rotations for all nodes along pile-cap/saddle wall junctions were enforced. ISS system The vessel support of the ISS system is independent of the surrounding steel. Accordingly, the platform column reac- tions are not required to design the saddle pile-caps. This system is used for vessels SV04 to SV06 in Figure 1. In some cases, it is recommended to use the ISS system for some types of vessels to eliminate load interactions. Figure 6 shows an example of the ISS system for the sulphur con - denser. The vessel is supported by concrete walls W5 and W6 separated by distance (L). The sliding saddle is attached to W5, and the fixed saddle is placed on W6. A removable

6 m

Critical PL column (Compression & shear)

5 m

Direction of motion

Critical PL column (Tension)

2.5 m

Case (A)

Fixed saddle

Sliding saddles

Critical Pile

6 m

5 m

D w

6 m

1.5 m

(a) INTS Case (A) support mechamism

7 m

Direction of motion

6 m

Case (B)

5 m

Saddle plate

Fixed saddle

Sliding saddle

A C

Critical Pile

Base plate

B C

7.5 m

Concrete wall

D w

5 m

Pile-cap

Piles

Critical Pile

(b) INTS Case (B) support mechamism (c) Section B-B

6 m

Teon coating

7 m

Anchor rods

Saddle wall

(d) Section A-A

(e) Section C-C

Figure 4 INTS loading mechanism

Figure 5 INTSS support system plan

PTQ Q4 2022