Section
2 Loading
2.1 General
2.1.1 This Chapter details the loads which are to be considered in the strength assessment
of the dock gate, see:
- Pt 2, Ch 2, 4 Global strength assessment;
- Pt 2, Ch 2, 5.1 Seismic assessment;
- Pt 2, Ch 2, 5.2 Fatigue assessment;
- Pt 2, Ch 2, 5.3 Impact assessment;
- Pt 2, Ch 2, 5.4 Temperature assessment; and
- Pt 2, Ch 2, 6 Local strength.
2.1.2 Where required by the designer/Operator, additional loads will be
specially considered.
2.2 Lightweight
2.2.1 Details of the calculated lightweight and its distribution are to be submitted.
2.3 Hydrostatic loads
2.3.1 Hydrostatic loads are to be based on the following:
- maximum operating water level, i.e. highest astronomical
tide;
- maximum credible water level, i.e. top of structure;
- minimum operating water level, i.e. lowest astronomical
tide; and
- maximum and minimum water level differences at which the
gate can be opened and closed.
2.3.2 The maximum water level cases are to consider the most extreme differential of height
possible between each side of the gate.
2.3.3 The maximum reverse head of water is also to be considered, i.e. maximum operating
water level on the reverse side with the corresponding minimum water level on the
opposite side.
2.3.4 Care is to be taken when selecting the maximum hydrostatic loads that the full
operational envelope of the dock gate has been considered.
2.3.5 When considering a seismic event, see
Pt 2, Ch 2, 2.6 Seismic loads, the maximum credible water
level is to be taken as the most likely level to be acting in conjunction with the
seismic event.
2.3.6 Wave loads are typically insignificant in comparison to maximum
hydrostatic loads, however, it may be necessary to consider wave loading in some
instances as part of the fatigue assessment, see
Pt 2, Ch 2, 5.2 Fatigue assessment.
2.4 Deck loading
2.4.1 The design loading acting on the top deck and internal decks of the dock gate is to
be taken as a 5 kN/m2 distributed load.
2.4.2 Where the top deck is used as a roadway, the details of the deck loading
resulting from the operation of vehicles are to be supplied by the designer. These
details are to include the wheel load, axle and wheel spacing, tyre print dimensions
and type of tyre for the vehicles. As a minimum, the distributed load is to be taken
as 10 kN/m2 and the concentrated load as 40kN acting on a 300 mm by 300
mm patch.
2.5 Wind loads
2.5.2 The wind pressure, p, acting on the structure is given
by:
Table 2.2.1 Force coefficient Cf
| Type
|
Description
|
Aerodynamic slenderness
l/b or l/D
|
| 5
|
10
|
20
|
30
|
40
|
50
|
| Individual members
|
Rolled sections, rectangles, hollow sections, flat
plates, box sections with b or d less than 0,5
m
|
1,30
|
1,35
|
1,60
|
1,65
|
1,70
|
1,80
|
| Circular sections, where
|
DVs < 6 m2/s
|
0,75
|
0,80
|
0,90
|
0,95
|
1,00
|
1,10
|
| DVs ≥ 6 m2/s
|
0,60
|
0,65
|
0,70
|
0,70
|
0,75
|
0,80
|
| Box sections
with b or d greater than 0,5 m
|
b/d
|
|
|
|
|
|
|
|
≥2,00
|
1,55
|
1,75
|
1,95
|
2,10
|
2,20
|
|
| 1,00
|
1,40
|
1,55
|
1,75
|
1,85
|
1,90
|
|
| 0,50
|
1,00
|
1,20
|
1,30
|
1,35
|
1,40
|
|
| 0,25
|
0,80
|
0,90
|
0,90
|
1,00
|
1,00
|
|
| Single lattice frames
|
Flat sided sections
|
1,70
|
| Circular sections, where
|
DVs < 6 m2/s
|
1,20
|
| DVs ≥ 6 m2/s
|
0,80
|
| Plated
structure
|
Plated structures on solid base (air flow beneath
structure prevented)
|
1,10
|
| Symbols
|
|
l |
= |
length of member, in metres |
|
D |
= |
diameter of circular section, in metres |
|
Vs |
= |
wind speed, in m/s |
|
b |
= |
breadth of box section, in metres |
|
d |
= |
depth of box section, in metres |
|
2.5.3 The wind force, Fw, acting on the structure is given
by:
where
|
A |
= |
is the effective area of the structure concerned, i.e. the solid area
projected on to a plane perpendicular to the wind direction, in
m2 |
|
p |
= |
is the wind pressure as defined in Pt 2, Ch 2, 2.5 Wind loads 2.5.2 |
|
Cf |
= |
is the force coefficient in the direction of the wind, as
defined in Table 2.2.1 Force coefficient Cf |
2.5.4 Wind suction acting on the back of the dock gate is also to be considered.
2.5.5 Wind loading is to be considered in association with the maximum credible water
level.
2.6 Seismic loads
2.6.1 Where a seismic assessment is carried out, the dock gate is to be capable
of withstanding seismic actions acting in all three orthogonal axes, including
vertical accelerations induced within the water column. Seismic inertial forces will
result from the combination of the lightweight of the dock gate and any trapped
water, with the motion resulting from the seismic action. Added hydrodynamic mass
effects should also be considered. The seismic motions are to be calculated in
accordance with a recognised National or International Standard.
2.7 Ice loads
2.7.1 Where required, increased mass due to icing is to be considered. If the ice accretion
values are not known, then 30 kg/m2 can be assumed for the horizontal
deck and 7,5 kg/m2 can be assumed for the vertical sides. The ice loads
are to be added to the lightweight for the purpose of the strength assessment.
2.8 Internal loads
2.8.1 The design head acting on tank bulkheads is to be taken as the distance from one
third above the bottom of the strake of plating to half the height of the overflow
above the tank top.
2.9 Air pressure test load
2.9.1 Where compressed air is used to expel water, the maximum test pressure is to be
applied to the affected structure.
2.10 Impact
2.10.1 Where an impact assessment is carried out, the loads are to be taken as follows;
- The impact loading resulting from dock gate manoeuvring can
be taken as 100 kJ if not otherwise specified.
- The impact loading resulting from a major ship collision (if
required) can be taken as 10 MJ if not otherwise specified. The shape of the
impacting body is to be agreed with the dock yard operators.
|