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Determination of loads shall include all loads resulting from the intended crane operation, and loads caused by the environment, in and out of service wind, erection, testing and fault conditions.

Steady-state loads, such as gravity-induced loads, shall be determined from the masses of all component parts permanently attached to the crane.

Live loads on in service cabin floor, walkways and platforms shall comply with the provisions of this Standard, AS 1657, AS 3990 and AS 1170.1.

Dynamic loads due to acceleration or deceleration of masses shall be determined by either—

(a) dynamic analysis capable of modelling the characteristics of the crane operations; or

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(b) methods of determination of loads specified in this Section.

7.4.2 Categorization of mechanism loads

For convenience of referencing, the mechanism loads are divided into three load groups as follows:

(a) Principal loads (see Clause 7.5).

(b) Additional loads (see Clause 7.6).

(c) Special loads (see Clause 7.7).

Each load group is divided into load categories as shown in Table 7.4.3.

7.4.3 Categorization of mechanism loading

The types of loading to be considered in the design of a crane mechanism, or mechanism component, shall be as shown in Table 7.4.3.

TABLE 7.4.3

CATEGORIZATION OF MECHANISM LOADS

Load group Loads Reference

Clause R1—Loads due to the dead load of the mechanism (or component) 7.5(a) R2—Loads due to the dead load of those parts of the crane acting on

the mechanism or component (including the empty mass of the crane hook) for those mechanisms (or components) that it acts upon directly or indirectly

7.5(b)

R3—Loads due to the mass of live load acting on the crane hook 7.5(c) R4—Loads due only to the dynamic effects caused by the maximum

acceleration (or retardation) of the mass loaded onto the crane hook

7.5(d) R5—Loads due to the maximum acceleration (or retardation) of the

crane mechanism (or component), including those due to the inertia of the mechanism itself, its prime mover, brakes, associated crane parts and the concurrent operation of other crane motions, as applicable

7.5(e)

R6—Loads arising from frictional forces

V1—Load due to the in service wind acting horizontally in any direction where applicable (see AS 1170.2)

7.5(f) 7.5(g) Principal loads

V2—Load due to the out of service wind acting horizontally in any direction where applicable (see AS 1170.2)

7.5(h)

Additional loads Wind, snow, ice, temperature extremes, oblique travel 7.6 B1—Load due to collision with buffers 7.7(a) Special loads

(see Clause 7.7)

B2—Emergency conditions 7.7(b)

7.5 PRINCIPAL LOADS

Principal loads comprise the mass of the mechanism and highly repetitive loads arising from the intended service of the mechanisms. The typical principal loads are as follows:

(a) R₁—loads due to the dead load of the mechanism (or component).

(b) R₂—loads due to the dead load of those parts of the crane acting on the mechanism or component (including the empty mass of the crane hook) for those mechanisms (or components) that it acts upon, directly or indirectly.

(c) R₃—loads due to the mass of live load acting on the crane hook.

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(d) R₄—loads due only to the dynamic effects caused by the maximum acceleration (or retardation) of the mass loaded onto the crane hook.

Where acceleration (or retardation) data is not available, the load increment due to the dynamic effects shall be calculated using the maximum suspended design deadload (payload) mass multiplied by (φ −1.0) where φ is typically φ2 or φ3 (see Clause 4.5.3.2 for a definition of φ2 and Clause 4.5.3.4 for a definition of φ3).

Care shall be taken in the determination of the dynamic multiplier for hoisting, that it is not underestimated, especially where high-speed hoisting is an available option.

(e) R₅—loads due to the maximum acceleration (or retardation) of the crane mechanism (or component), including those due to the inertia of the mechanism itself, its prime mover, brakes, associated crane parts and the concurrent operation of other crane motions, as applicable.

(f) R₆—loads arising from frictional forces.

(g) V₁—load due to the in service wind acting horizontally in any direction, where applicable (see AS 1170.2).

The loads on the mechanism shall be determined from the most adverse wind conditions on the crane structure and securing devices, e.g., rail clamps.

In general, the torque (M_Au) forced onto the driving mechanism by the wind load is limited by sliding of the track wheels or by braking. The maximum value of M_Au from one of the following equations shall apply:

(i) = ( _{Au L})

a

Au L W P

i

M r − . . . 7.5(1)

(ii) _Au

a

Au = L R

i

M µ r Σ . . . 7.5(2)

(iii) M_Au =i_m M_br . . . 7.5(3)

where

M_Au = maximum torque on the driving mechanism due to wind load

r_L = radius of track wheel, with driving mechanisms, or distance of the thrust point of the wind from the rotary axle, with slewing, luffing or pull-in mechanisms

i_a = gear ratio of the driving mechanism shaft to be calculated to the track wheel or rotary crane part

W_Au = the wind load acting on the in service driving mechanism in accordance with AS 1170.2

P_L = proportion of the resistance to travelling, traversing, luffing, pulling-in or revolvpulling-ing as actpulling-ing on the drivpulling-ing mechanism

µ = coefficient of friction between the track wheel and rail to be taken as 0.25

Σ RAu = total of the maximum wheel forces of the track wheels connected to the driving mechanism in the in service condition

i_m = gear ratio from motor to part under consideration

M_br = maximum torque in the motor shaft from the mechanical brake or the motor or the eddy current brake

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(h) V₂—load due to the out of service wind acting horizontally in any direction, where applicable (see AS 1170.2).

For the out of service condition, the driving mechanisms are generally idle, but frequently they have to perform a static function, e.g., holding in place against the wind. On occasions, they are influenced more unfavourably by a different distribution of the dead load than when operating. For cranes with booms, wind loads shall be considered in fatigue calculations.

7.6 ADDITIONAL LOADS

Additional loads and their effects occur relatively infrequently and are usually neglected in fatigue evaluations. Typical additional loads are due to snow, ice, temperature extremes and oblique travel.

7.7 SPECIAL LOADS

The combinations of loads to be considered for special loading conditions depend upon the type of crane, the application and the crane motion. It shall include any loading conditions that are known to apply but which are not covered under the loading conditions given in Table 7.9.

NOTE: During erection or dismantling operations unless the operation is completed during a period when the wind does not exceed V₁ conditions, the parts being erected or dismantled should be secured so that they are capable of withstanding a wind of V₂ conditions.

Special loads occur during operations on such rare occasions that there is no need to take them into consideration with regard to the service life of the respective driving mechanism parts. Three types of special loads that should be taken into consideration are out of service wind, buffer forces and emergency shutdown or power failure. These may be considered as follows:

(a) B₁—driving mechanism loads due to collision with buffers The driving mechanism parts shall be assessed for maximum load sustained during impact of the crane or parts of the crane onto travel buffers or end stops.

Where driving mechanisms rely on friction, accurate loads may be calculated by taking the sliding force between the track wheel and the rail as a basis for the calculation of the torque (M_SO) in accordance with the following equation:

a max

SO L R

i

M = µ r Σ . . . 7.7

where

µ, rL and i_a are as defined in Clause 7.5

Σ Rmax = total of the maximum wheel forces of the track wheels driven by the driving mechanism under consideration during operation

(b) B₂—Emergency conditions Emergency shutdown or power failure

Where driving mechanisms, apart from the in service brake, have an additional safety or holding brake that becomes effective without delay in the event of power failure, the torque occurring with application of this brake shall be determined.

The maximum braking torque of the in service, safety and holding brakes shall be applied.

For driving mechanisms relying on friction, use Equation 7.7.

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7.8 CATEGORIZATION OF FREQUENCY OF MECHANISM LOAD