(a) Load considerations
The loads to be taken into the calculation of dimensions of structural members are to be those related to the crane concerned among the items enumerated from (i) to (xi) below:
(i) Safe working load of the cranes.
(ii) Additional impact loads.
(iii) Self-weight of crane system and cargo fittings attached thereto.
(iv) Self-weight of loose gear.
(v) Friction of cargo blocks.
(vi) Horizontal forces.
(vii) Wind loading.
(viii) Buffer forces.
(ix) Loads due to ship inclination.
(x) Loads due to ship motion.
(xi) Other loads considered necessary by the Society.
(b) Additional impact loads
(i) The additional impact load is to be the product of the hoisting load and the impact load coefficient given in Table 9.1 depending on the type of cranes. When the stress due to hoisting of cargo and the stress due to the self weight have different signs in a member, 50 ％ of additional impact load is to be taken into account in addition to the self-weight, considering the shock due to unloading.
(ii) Notwithstanding the requirements specified in (i) above, additional impact load coefficient based on actual measurements taking into account the hoisting speed, deflections of girders, length of ropes, etc. may be used in place of the values given in Table 9.1.
Table 9.1
Additional Impact Load Coefficient
Types of cranes Additional impact load coefficient Provision handling crane, Machinery handling crane,
Maintenance crane and Hose handling crane 0.10
Jib crane and gantry crane for cargo handling 0.25
Jib crane and gantry crane occasionally used with hydraulically operated of rope-operated bucket, etc. for cargo handling
0.40
Jib crane and gantry crane always using grab, lifting
magnet, etc. for cargo handling and Offshore jib crane 0.60 (c) Friction of cargo blocks
The friction of cargo blocks is to be as specified in 8.1(b).
(d) Horizontal forces
(i) In track-mounted cranes, the transverse forces due to travel motion is to be taken into consideration as a factor of horizontal force in addition to the inertial force and centrifugal force.
(ii) The inertial force is to be obtained by multiplying the sum of the mass of the moving parts and the hoisting load (in slewing motion, the load is assumed to be at the top of jib) by the following coefficient depending on the condition of motion. In the case of traveling by driven wheels, however, this inertial force need not exceed 15％ of the driving wheel load.
Level luffing motions : 0.01V1/2
Traversing or traveling motions: 0.008V1/2 Slewing motions : 0.006V1/2
Where
V = Velocity of motion concerned to be determined by the designer, m/min
(iii) Notwithstanding the requirements in (ii) above the values of the actual acceleration deceleration characteristics, the actual braking time, etc. for the mode of motion concerned may be used as the inertial forces, if such values are known.
(iv) For a system having structural members which will make slewing motions while supporting the safe working load, the centrifugal force determined from following formula is to be taken into
consideration : (Wυ2)/R kN where:
W = Safe working load, t.
R = Slewing radius, m.
υ = Circular speed, m/sec.
(v) The transverse force due to travel motions is to be calculated from the following formula:
λD kN where:
D = Wheel load, kN.
= Transverse force coefficient to be determined from the following formula depending on the value of l/a. However, need not exceed 0.15 :
0.05 for (l/a) ≤ 2 [(l/a) + 1]/60 for (l/a) > 2 l = Span of rails, m.
a = Effective wheel base to be determined according to Fig. 9.1, m.
Fig. 9.1
Measurement of Effective Wheel Base
(e) Wind loading(i) The wind loading is to be calculated by the following formula:
F＝PA / 1000 kN
a
(a) Four wheels on one rail
(b) Eight wheels on one rail
(c) More than eight wheels on one rail
a
a
where:
F = Wind loading, kN.
A = Sum of structural members and cargo under wind pressure in projection in respective wind direction, corresponding to respective conditions of the cargo gear, m2. When a girder is wholly or partly protected from wind by another girder, the areas of the superposed portions may be multiplied by the reduction factor, , obtained from Fig. 9.2. The distance b between girders is to be as given in Fig. 9.3.
Fig. 9.2
Repleteness Ratio, Φ versus Reduction Factor,
Fig. 9.3
Distance between two neighbour- ing girders, b
P = Wind pressure calculated by the following formula, Pa.ChCsgV2/16 Pa where:
V = Wind velocity according to (1) and (2) below, m/sec:
(1) The velocity of wind giving effect on the structural members and cargo in the service
conditions is to be the design wind velocity specified by the applicant, but not be less than 16 m/sec.
(2) The velocity of wind giving effect on the structural members in the stowage conditions is to be the design wind velocity specified by the applicant. In no case is the design wind velocity to be less than 51.5 m/sec. In ships with restricted navigation areas, however, the design wind velocity may be decreased according to the degree of restriction as approved by the Society in the range down to 25.8 m/sec.
Ch = “Height factor” to be determined according to Table 9.2 depending on the height of the position is question from the light weight waterline.
Cs = “Shape factor” to be determined according to Table 9.3 depending on the shapes of various parts of the cargo gear and the cargo.
(ii) Notwithstanding the requirements in (i) above, the data on wind loading obtained by wind tunnel tests for the structural members and cargo may be used for calculations.
Table 9.2 Height Factor, C
hVertical height h (m) Ch
h＜15.3 15.3 ≤ h＜30.5 30.5 ≤ h＜46.0 46.0 ≤ h＜61.0 61.0 ≤ h＜76.0 76.0 ≤ h
1.00 1.10 1.20 1.30 1.37
As value considered appropriate by the Society
Table 9.3
Shape Factor C
sType of area under wind pressure Cs
Truss of angle <0.1
0.1≤<0.3 0.3≤<0.9 0.9≤
2.0 1.8 1.6 2.0 Plate girder or box girder (l/h)<5
5≤ (l/h)<10 10≤ (l/h)<15 15≤ (l/h)<25
1.2 1.3 1.4 1.6 Cylindrical member or truss
of cylindrical member
d q<1.0 1.0≤d q
1.2 0.7
Note:
= Repleteness ratio equal to the ratio of projected area under wind pressure to the projected area surrounded by the outer contour of the area under wind pressure.
l = Length of plate girder or box girder, m.
h = Height of plate girder or box girder looked at from windward, m.
d = Outer diameter of cylindrical member, m.
q = Value calculated by the following formula : (gChV2/16)×10-3 kPa
(f) Buffer forces
(i) The buffer forces are assumed to be the loads in the crane system originating from collision with buffer at a speed equal to 70％ of the rated speed when no cargo is suspended from the crane. In a crane system having a rigid guide, etc. to limit the swinging of suspended cargo due to collision, the influence of the cargo weight is also to be taken into consideration.
(ii) Notwithstanding the requirement in (i) above, in a crane system designed to be automatically decelerated before colliding the buffer, the speed after deceleration may be regarded as the rated speed in the requirement in (i) above.
(g) Loads due to ship inclination h
h l
l h
h
The angles of inclination used for the calculation of loads due to ship inclination are not to be less than the values specified below:
(i) In service conditions : 5º in angle of heel and 2º in angle of trim occurring simultaneously.
(ii) In stowage conditions : 30º in angle of heel.
(h) Loads due to ship motion
The accelerations used for the calculation of loads due to ship motion are the severest of the combinations (i) or (ii) below for the stowage condition, and values recognized by the Society to be appropriate for the service condition. If data on the ship’s motions are submitted and recognized by the Society to be appropriate, the values in such data may be used in the calculations.
(i) ±1.0 g in the direction normal to the deck and ±0.5 g in the longitudinal direction parallel to the deck.
(ii) ±1.0 g in the direction normal to the deck and ±0.5 g in the transverse direction parallel to the deck (i) Load combinations
(i) The load to be used in the strength analysis of structural members is to be such a combined load that these members may be put in the severest loading condition considering the loads specified in (ii) through (v) below.
(ii) When the wind loading is not taken into account in service condition, the sum of loads from (1) to (9) below multiplied by a work coefficient given in Table 9.4 according to the type of crane concerned is to be considered.
(1) Safe working load of the cranes.
(2) Additional impact loads.
(3) Self-weights of crane system and cargo fittings attached thereto.
(4) Self-weights of loose gear.
(5) Friction of cargo blocks.
(6) Horizontal loads.
(7) Loads due to ship inclination.
(8) Loads due to ship motion (except those intended to cargo handling in harbours only).
(9) Other loads considered necessary by the Society.
Table 9.4
Work Coefficient of Crane Systems
Types of cranes Work coefficient
Provision handling crane, Machinery handling crane,
Maintenance crane and Hose handling crane 1.00
Jib crane and gantry crane for cargo handling 1.05 Jib crane and gantry crane occasionally used with
hydraulically operated of rope-operated bucket, etc. for cargo handling
1.10 Jib crane and gantry crane always using grab, lifting
magnet, etc. for cargo handling and Offshore jib crane 1.20
(iii) When the wind loading are to be taken into consideration in the service conditions, the wind loading is to be added to the design load as specified in (ii) above.
(iv) The buffer forces as given in 9.1(f) are to be taken into consideration for the track-mounted cranes.
(v) In stowage condition, the loads from (1) to (5) below are to be considered (1) Self-weights of crane system and cargo fittings attached thereto.
(2) Wind Loading in the stowage conditions.
(3) Loads due to ship inclination in the stowage conditions.
(4) Loads due to ship motion stowage conditions.
(5) Other loads considered necessary by the Society.
9.2 Strength and construction (a) General
(i) The strength of structural members is to be analyzed on the load conditions specified in 9.1(i) to determine their dimensions according to requirements in 9.2(b) through 9.2(i).
(ii) For structures connected by bolts and nuts, proper considerations are to be given to the decrease of effective sectional areas.
(iii) When considered necessary the Society may require the confirmation of the appropriateness of strength analyses by examination of models or the things in question.
(b) Allowable stress for combined loads
The allowable stress given in Table 9.5 are to be used for components subjected to combined loads.
(c) Buckling strength
For members subjected to compression, the values obtained from the following formula is not to exceed the allowable compressive stress given in Table 9.5:
ωσc N/mm2 where:
ω and σc = As specified in 8.3(c).
Table 9.5 Allowable Stress σ
aLoad Condition
Kind of stress (Tens.= tension; Bend.= bending; Comp. = compression; Bear. = bearing.; Comb. = combined stress)
Tens. Bend. Shear Comp Bear. Comb.
Condition given in 9.1(i)(ii) 0.67σy 0.67σy 0.39σy 0.58σy 0.94σy 0.77σy
Condition given in 9.1(i)(iii) 0.77σy 0.77σy 0.45σy 0.67σy 1.09σy 0.89σy
Condition given in 9.1(i)(iv) and (v) 0.87σy 0.87σy 0.50σy 0.76σy 1.23σy 1.00σy
Notes:
1. σy =The yield point or proof stress of material, N/mm2.
2. The combined stress is to be the value obtained from the following formula:
(σX
2 σY2 σXσY 3τXY 2)1/2 N/mm2 where:
σX = Applied stress in X-direction at the middle of plate thickness, N/mm2. σY = Applied stress in Y-direction at the middle of plate thickness, N/mm2. τXY = Applied shear stress in the X-Y plane, N/mm2.
(d) Combined compressive stress
When the compressive stress of a member is determined as a combination of compressive stress due to axial compression and that due to bending moment such a compressive stress is to comply with the following formula:
[(σc/σca) + (σb/σa)] ≤ 1.0 where:
σa = Allowable bending stress given in Table 9.5, N/mm2. For fixed posts at the base, however, the allowable stress in Table 8.1 is to be used.
σb = Compressive stress due to bending moment, N/mm2. σc = Compressive stress due to axial compression, N/mm2.
σca = Allowable compressive stress given in Table 9.5, N/mm2. For fixed post at the base, however, the
allowable stress, N/mm2, is to be taken equal to the allowable stress in Table 8.1 divided by 1.15.
(e) Fatigue strength
Where the influence of repeated stress cannot be neglected, the member is to have an ample strength against fatigue with due consideration for the magnitude and frequency of repeated stress, the form of the member in question, etc.
(f) Minimum thickness
The thickness of structural members is not to be less than 6 mm.
(g) Strength of bolts, nuts and pins
Bolts, nuts and pins are to have sufficient strength for the magnitudes and directions of the loads they are subjected to.
(h) Fixed posts
(i) The fixed posts are to be effectively connected to the hull structure in accordance with the requirements in 8.2(d)(i).
(ii) The upper part of fixed post where the flange is attached is to be sufficiently reinforced by increasing the plate thickness or by providing of brackets.
(i) Slewing-ring fixing bolts
(i) Any material having a tensile strength exceeding 1,180 N/mm2 and yield stress exceeding 1,060 N/mm2 is not to be used for the bolts fixing the slewing-rings except when special considerations have given to the strength characteristics of the bolts.
(ii) Special considerations are to be given to the tightening force of fixing bolts.
(iii) The stress generated in fixing bolts is not to exceed the allowable stress given in Table 9.6 according to the load conditions specified in 9.1(i). In this case, the stress in bolts is taken as the value of the axial compression determined by the following formula divided by the minimum sectional area of fixing bolts.
(4M/Dn) (W/n) N where:
M = Upsetting moment, N-mm.
D = Pitch circle diameter of fixing bolts, mm.
n = Number of fixing bolts.
W = Axial compression on the slewing-ring, N.
Table 9.6
Allowable Stress of Fixing Bolts, σ
aLoad condition σa
Condition specified in 9.1(i)(ii) and (iii) 0.4σy
Condition specified in 9.1(i)(v) 0.54σy
Note: σy = The yield point or proof stress of the material, N/mm2. 9.3 Special requirements for track-mounted cranes
(a) Stability
The track-mounted cranes are to have an sufficient stability under the load conditions specified in 9.1(i).
(b) Prevention of upsetting
The track-mounted crane are to be designed with sufficient considerations for the stability to prevent upsetting even if the wheel shafts or wheels are damaged.
(c) Deflection criteria
When suspending the safe working load, deflection of the traveling girder of the track-mounted cranes is not to exceed 1/800 of the span between the supporting points.
(d) Travel gear
The travel gear is to be securely fixed to the main body of the track-mounted cranes by bolts, welding or pins. The inclinations of hull in service condition and stowage condition are to be taken into consideration.
(e) Buffers
The track-mounted cranes are to be provided with buffers in accordance with (i) and (ii) below, except when automatic system for prevention of collision is provided.
(i) At both ends of tracks or any other equivalent positions, these buffers may be replaced by stops of a height not less than 1/2 of the diameter of wheels.
(ii) Where more than two track-mounted cranes are provided on one track, between these track-mounted cranes.