ANEXOS
A.6. Dimensionado de barras
Crane wheels and rails form a mutually interactive system. Wheels and rails shall comply with Clauses 7.20.3 and 7.20.6 respectively, and their selection shall take into account the following:
(a) Wheel loading (known or assumed).
(b) The service to which the crane shall be subjected.
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(c) Grade of material of wheels and of rails.
7.20.2 Wheel loading
For design purposes, the mean wheel loading (PW mean) shall be calculated, without application of the dynamic factors specified in Section 4, by the following equation:
3
PW mean = the maximum unfactored wheel loading, in kilonewtons
PW min = loading applied by the wheel to the rail with the crane arranged within its normal range of in service conditions (including loading) to produce minimum loading between the wheel and rail, in kilonewtons
PW max = loading applied by the wheel to the rail with the crane arranged within its normal range of in service conditions (including loading) to produce maximum loading between the wheel and rail, in kilonewtons
For the purpose of design of the wheel, PW max shall be not less than the maximum load due to exceptional circumstances such as where a tall gantry crane in an exposed location is subjected to very high wind loading and where a crane is subjected to frequent buffer collisions.
The value of PW min shall be taken for load combinations 1 to 5 (frequently occurring loads) and in no case shall wind load be included.
7.20.3 Wheels 7.20.3.1 Material
The material for track wheels shall comply with the relevant Australian Standard (refer Table 7.20.3.3).
7.20.3.2 Load capacity of wheels (PW)
The wheel load (PW mean) calculated in accordance with Clause 7.20.2 shall be not greater than the permissible wheel load (PW) calculated by the following equation:
pW
PW = permissible wheel loading, in kilonewtons
CC = group classification coefficient (see Clause 7.20.3.4) CW = wheel-speed coefficient (see Clause 7.20.3.5)
DW = wheel-tread diameter, in millimetres
BWE = effective wheel-tread width is equal to BTE in Clause 7.20.6.5(a) and (b) or where not applicable, from Clause 7.20.3.6(c)
FpW= permissible unfactored bearing stress between wheel and rail (see Clause 7.20.3.3), in megapascals.
7.20.3.3 Permissible unfactored bearing stress (FpW)
The unfactored bearing stress between wheel and rail (FpW) shall be calculated by the following equation or selected from Table 7.20.3.3:
uW pW 1.5 0.007F
F = + . . . 7.20.3.3
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where
FpW = permissible unfactored bearing stress between wheel and rail, in megapascals FuW = tensile strength of wheel material or, where the wheel is tyred, the tyre
material, in megapascals.
Where the wheel tread is surface-hardened, FpW shall apply to the tensile strength of the material prior to surface hardening.
For wheels other than ferrous-metal wheels, the value used for FpW shall be as recommended by the manufacturer.
TABLE 7.20.3.3
PERMISSIBLE UNFACTORED BEARING STRESS
1 2 3 4 5 6
runway rails shall be continuous
Steel forging AS 1448
K3
7.20.3.4 Group classification coefficient (CC)
The value of the group classification coefficient (CC) shall be the appropriate value specified in Table 7.20.3.4 corresponding to the classification applicable for the crane-motion in which the wheel is used.
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TABLE 7.20.3.4
7.20.3.5 Wheel-speed coefficient (CW)
The value of the wheel-speed coefficient (CW) shall be the appropriate value specified in Table 7.20.3.5.
TABLE 7.20.3.5
WHEEL-SPEED COEFFICIENT (CW)
Rotational
7.20.3.6 Tread and flange profile The following applies:
(a) Profile Typical tread and flange profiles are shown in Figure 7.20.3.6. Other (special) profiles are used for particular specialized applications.
The wheel type shall correspond to the wheel track with which it is used in accordance with Table 7.20.3.6(A).
(b) Tread and flange dimensions The thickness (TF) of each flange (see Figure 7.20.3.6) shall be not less than the following when new:
(i) if DW≤ 400 mm;
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(ii) if DW > 400 mm;
TF = flange thickness (see Figure 7.20.3.6), in millimetres DW = wheel tread diameter, in millimetres
The minimum flange thickness (TF′) shall be calculated as follows, and this information shall be provided with the crane in accordance with Clause 16.3:
NOTE: The minimum flange thickness (TF′) is to be provided with the crane to allow users to institute a replacement regime to ensure flange thicknesses below TF′ are not used.
X
Ft = permissible bending strength, MPa (see Clause 7.9.2.8) X = length of rail to wheel flange engagement (mm)
P = oblique travel force (see Clause 4.6.5) OT
H = flange depth (mm) F
The height of the flange (see Figure 7.20.3.6) shall be not less than +10 50W
D .
For a double-flanged wheel, the tread width (see Figure 7.20.3.6) shall be not less than the width of the railhead, plus twice the rail span tolerance (Table 7.20.9), plus the manufacturer’s tolerance of span of the crane, plus 4 mm, except where wheels on the opposite rail are laterally free in position.
Where the clearance between wheel flanges and railheads permits lateral float greater than one-fourth of the width of the railhead, care shall be taken to ensure that lateral movement does not affect clearances (see Clause 12.7.4) and correct operation of electrical collectors (see Clause 8.14).
A1
A1
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(c) Effective wheel-tread width (BWE) The effective wheel-tread width (BWE) shall be as specified in Table 7.20.3.6(B).
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FIGURE 7.20.3.6 TYPICAL WHEEL-TREAD PROFILES
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TABLE 7.20.3.6(A)
TREAD AND FLANGE PROFILE
Wheel track
Flanges of each type may be tapered or parallel sided
For Types A, D and G, the fillet radius between tread and flange shall be not less than the railhead radius
Standard rail section (i.e.
conforming to AS 1085.1)
Unflanged With cylindrical tread B
Flanges of each type may be tapered or parallel-sided
Square or rectangular billet or similar section
Unflanged With cylindrical tread
G J K L N
Flanges of each type may be tapered or parallel-sided
Type M may be used where the wheel axle is canted to compensate for the wheel-tread angle In applications of intermittent and light-duty loadings, type M may be used without the provision specified above, although this is not good practice
Flange, having a horizontal wheel-track surface, of a beam, girder or similar structural element
Unflanged
With cylindrical, symmetrical or asymmetrical-spherical tread
With tapered tread may be used where the wheel axle is canted to compensate for the wheel-tread angle
K L M N
Flanges for each type may be tapered or parallel-sided
Type G, H or J may be used where the wheel axle is canted to compensate for the beam-flange taper angle
In applications of intermittent and light-duty loadings, Type G, H or J may be used without the provision specified above, although this is not good practice
Beam flange, having an inclined wheel-track surface (e.g., tapered-tread beam)
Unflanged
With tapered, symmetrical-spherical or asymmetrical-spherical tread
With cylindrical tread may be used where the wheel axle is canted to compensate for the beam-flange taper angle
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TABLE 7.20.3.6(B)
EFFECTIVE WHEEL-TREAD WIDTH (BWE)
Wheel track Wheel type Effective wheel-tread width (BWE) Double-flanged if on convex surface rail
Cylindrical or tapered tread (see Figure 7.20.3.6)
BW (see Figure 7.20.3.6 or Clause 7.20.3.7) Flange of beam,
girder or similar Symmetrical spherical tread (see Note) Figure 7.20.3.6), whichever is the lesser
Tapered flange of beam, girder or similar
Asymmetrical spherical
tread (see Figure 7.20.3.6) BW (see Figure 7.20.3.6) or 0.2 RWT* (see Figure 7.20.3.6), whichever is the lesser
* The values of 0.2RWT and 0.1RWT assume contact between wheel tread and wheel-track surface to extend 0.09 radius of wheel-tread arc from the central point of contact.
NOTE: Where a wheel with symmetrical spherical tread runs on a tapered flange, the central point of contact is displaced towards the unflanged side by an amount equal to RWT times the sine of the flange-taper angle. Where the remaining distance is less than 0.1RWT, the effective wheel-tread width shall be reduced accordingly (see Figure opposite).
LEGEND:
BWE = effective wheel-tread width, in millimetres BT = railhead width, in millimetres
RT = railhead radius, in millimetres BW = wheel-tread width, in millimetres
RWT = wheel-tread radius (spherical wheel-tread), in millimetres
7.20.3.7 Unflanged wheels
Unflanged wheels shall be used only where provision is made for lateral guidance of the crane or part of the crane supported by the wheels, e.g., by guide rollers.
The tread width (BWE) of a cylindrical or tapered-tread unflanged wheel shall be the width of the tread, excluding corner radii for flat rails or excluding 4/3 of corner radii for convex rail heads.
7.20.3.8 Matched wheels
Where driving wheels are connected together mechanically, the difference in the tread diameter shall not exceed 0.1 percent of the larger diameter or 0.25 mm, whichever is the lesser.
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7.20.3.9 Overhung wheels
Where a track wheel or guide roller is overhung, i.e. cantilevered, positive means shall be provided to retain the wheel on its axle in service.
7.20.3.10 Anti-drop and anti-derailment pads
For safe operation, anti-drop and anti-derailment pads, where applicable, shall be provided as specified by the appropriate part of AS 1418.
For a crane or part of a crane running on rails, means shall be incorporated in the structure of the crane, or part of the crane, to prevent it from falling more than 25 mm and from excessive lateral movement in the event of wheel or axle failure.
7.20.4 Tyres
Where a crane wheel is fitted with a steel tyre, the nominal inside diameter of the tyre should conform to Table 7.20.4.
TABLE 7.20.4 TYRE INSIDE DIAMETER
Nominal tread diameter Nominal inside diameter 400
Side guide rollers shall comply with the requirements for unflanged wheels specified in Clause 7.20.3.7.
7.20.6 Rails 7.20.6.1 Material
Rails shall comply with AS 1085.1 or DIN 536-1, or shall be of other suitable rolled-steel section and shall be designed for a 25 year life if permanently attached (e.g., welded) or may be designed for a 10 year life if easily removable (e.g., held by hook-bolts or clips).
7.20.6.2 Load capacity of rail (PT)
The wheel loading (PW mean) applied to a rail and calculated in accordance with Clause 7.20.2 shall be not greater than the permissible mean wheel load on rail (PT) calculated by the following equation:
TS R
T C P
P = . . . 7.20.6.2
where
PT = permissible mean wheel loading on rail, in kilonewtons
)
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PTS = permissible unfactored wheel loading on rail (see Clause 7.20.6.4), in kilonewtons
NXW= number of stress cycles applied by the wheels to the rail at the most frequently used portion of the rail (see Clause 7.20.6.3)
NOTE: A stress cycle occurs at any position along a rail when the bearing stress in the railhead fluctuates through a cycle due either to movement of a wheel along the rail or to variation of loading through a stationary wheel when the crane load is handled through a load cycle with the crane, or part of the crane, stationary.
Where cranes of different classes operate on the same section of crane track, PT shall be calculated directly from the equation specified in this Clause, NXW being the sum of the number of stress cycles due to the wheels of each crane.
7.20.6.3 Number of stress cycles applied by wheels to rail (NXW)
The number of stress cycles applied by wheels to a rail (NXW) (see Clause 7.20.6.2) shall be determined by the following equation except where specified otherwise in the appropriate part of AS 1418:
Un = number of load applications of crane over design life of crane where Un varies from U0 to U9 as defined in Table 2.3.2
NOTE: The values for the number of operating cycles given in Table 2.3.2 may be adjusted proportionally to allow for the lesser design life of components with a minimum being 40% to allow for a minimum design life of 10 years for readily removable rails (e.g., attached by hook-bolts or clips).
NW = number of wheels which travel along a crane rail 7.20.6.4 Permissible unfactored wheel load (PTS)
For the rails listed in Table 7.20.6.4, the permissible unfactored wheel load on a rail (PTS) shall be calculated from the following equation:
TS W
TS D p
P = . . . 7.20.6.4(1)
where
PTS = permissible unfactored wheel loading, in kilonewtons DW = wheel tread diameter, in millimetres
pTS = permissible load (see Table 7.20.6.4), in kilonewtons per millimetre (of wheel diameter)
For rails other than those listed in Table 7.20.6.4, the permissible unfactored wheel load (PTS) shall be calculated from the following equation:
p
BTE = effective railhead width (see Clause 7.20.6.5), in millimetres Cp =
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FYT = yield stress of rail material, in megapascals TABLE 7.20.6.4 PERMISSIBLE LOAD (pTS)
Rail profile
7.20.6.5 Effective railhead width (BTE)
The effective railhead width (BTE) shall be calculated by the following equations:
(a) Where the top surface of the railhead is flat—
CR T
TE B 2R
B = −
(b) For standard rail sections with convex top railhead surface with one corner radius—
CR
(c) For American Railway Engineering Association (AREA) type rail with railhead surface determined by three radii with two corner radii—
BTE BT 3
=2
where
BTE = effective railhead width, in millimetres BT = railhead width, in millimetres
A1
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7.20.7 Rail fastening and joining 7.20.7.1 Methods
Rails shall be secured to the runway beams or crane girder by a method that takes into account—
(a) horizontal wheel forces induced in the rail;
(b) rail alignment requirements;
(c) duty of the runway system;
(d) rail profile; and
(e) rail material specification.
7.20.7.2 Welding
7.20.7.2.1 Rail section profiles
Securing rail to runway girders by welding shall be limited to sections less than or equal to 40 kg/m rail profiles.
The welding procedure applied to securing the rail to the runway beam shall take into account the following:
(a) Matching section thicknesses.
(b) Differences in rail and girder material specification.
(c) Magnitude of induced stresses, including longitudinal bending shear stress, fatigue and weld shrinkage residual stress.
(d) Pre-heat-treatment and post-heat-treatment.
7.20.7.2.2 Billet sections
The design of the weld, securing the billet to the top flange of the runway or crane girder, shall be sized to take into account the longitudinal shear stresses due to bending.
The welding procedure applied to securing the billet to the runway beam shall take into account the factors outlined in Clause 7.20.7.2.1.
7.20.7.3 Direct bolted
Where the rail is bolted directly to supporting steelwork, the rail and steelwork shall be match-drilled.
7.20.7.4 Hook bolts
Hook bolts are suitable for use on standard rail sections less than or equal to 30 kg/m profiles and where the top flange of the runway beam is too narrow for the application of a rail clip or clamp.
The hook bolts shall be placed on alternate sides of the rail at 75 mm to 100 mm centres, spaced at centres no greater than 600 mm.
Each hook bolt shall be secured by a lock nut after final positioning.
Finished hook bolts shall be able to be straightened by at least 50% of the deformation during manufacture under the test without brittle fracture. Verification shall be carried out by testing at least one sample from each batch.
NOTES:
1 Ductile hook bolts are necessary to prevent fracture and falling of the bolts and the resulting hazard to personnel under the runway.
2 Hook bolts do not allow longitudinal movement of the rail. Hence, it is recommended that
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7.20.7.5 Rail clips
Rail clips are either forged, cast or fabricated devices that have been shaped to suit the flange shape of a particular rail profile.
Rail clips secure the rail in position by a clamping action on the flange with a single bolt.
This bolt can be either a through bolt on the top flange of the runway girder or integral with the clip base plate which, in turn, has been welded to the girder top flange adjacent to the rail.
Clips shall be designed to—
(a) prevent rotation of the clip due to longitudinal movement of the rail; and
NOTE: Where rotation of the clip cannot be prevented, a system of snug block located midway between the clips can be used to prevent lateral drift of the rail. The snug blocks should be welded to the girder top flange adjacent to the rail in its correct position.
(b) develop the full strength of the securing bolt.
The clip shall be secured by a locking nut to prevent loosening in service.
The clips shall be arranged in pairs located on opposite sides of each side of the crane rail and spaced at centres not greater than 600 mm, or as recommended by the competent person or manufacturer.
NOTE: Rail clips are best suited for duty on runways with a duty classification of less than or equal to C4.
7.20.7.6 Rail clamps
Rail clamps are either forged, cast or fabricated devices that have been shaped to suit the flange shape of a particular rail profile.
The clamps secure the rail in position by a clamping action on the flange with two bolts.
These bolts can be either a through bolt on the top flange of the runway girder, or integral with the clamp base plate which, in turn, has been welded to the girder top flange adjacent to the rail.
The clamps shall be designed to—
(a) prevent rotation of the clip due to longitudinal movement of the rail; and
NOTE: Where the clamp design does not prevent lateral drift of the rail, a system of snug blocks located midway between the clamps can be used. The snug block should be welded to the girder top flange adjacent to the rail in its correct position.
(b) develop the full strength of the securing bolts.
The clamp bolts shall be secured by a locking nut to prevent loosening during service.
The clamps shall be arranged in pairs located on opposite sides of each side of the crane rail and spaced at centres not greater than 900 mm, or as recommended by the clamp designer or manufacturer.
NOTE: Rail clamps are best suited for duty on runways with a duty classification of greater than or equal to C5.
7.20.7.7 Laid-on sleepers
Where rails are laid on timber, concrete, steel or other types of sleepers, the rail shall be attached by means of dog-spikes or other attachment of strength appropriate to the rail with which they are used. Spacing shall be at sufficiently close centres to retain the rail in alignment as specified in Clause 7.20.9.
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7.20.8 Rail joints
The number of gaps in the length of a rail system should be minimized. Where a gap in the rail is needed for expansion or other purposes, the top face of the rail shall be flush, and the gap distance shall be not greater than 3 mm. Rail joints should not coincide with a joint in the rail-supporting structure or a joint on the opposite runway.
Fishplates or equivalent means of maintaining joint alignment shall be provided at all non-welded joints of standard rail sections.
The shock loading effects of joints on crane runway systems classified greater than C5 cannot be underestimated. It is recommended that fully welded continuous rail is used in these applications.
The welding process used for joining rails shall take into account—
(a) the rail material specification;
(b) appropriate pre-weld heating and post weld cooling;
(c) the effects of weld shrinkage on the rail system; and
(d) surface hardness of the welded joint, to minimize dips developing in the joint during service.
7.20.9 Rail alignment
Each pair of rails shall be aligned within the limitations set out in Table 7.20.9.
7.20.10 Runway flanges—Lateral support
The top flange on all runway beams at the point of support should be braced directly to the column or other supporting structure to prevent lateral movement.
NOTE: AS 1418.18 gives further guidance on the design of crane runways and monorails.
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www.standards.com.au Standards Australia 81AS 1418.1—2002
TABLE 7.20.9 RAIL ALIGNMENT
Description Tolerances for
crane classes C1 to C4
Tolerances for crane classes
C5 to C9 ST≤ 15 m: A = ±3 mm
ST > 15 m: A = ±[3 + 0.25 × (ST – 15)] mm Span, centre-to-centre of rails
Where ST is in metres
Where ST is in metres