The main difference between the configurations of these hoisting devices is the working load limit (WLL); see also «lifting point». From commercially catalogues of overhead travelling crane suppliers, it is generally found that :
for heavy loads, the topmounted crane bridges have a capacity up to 1200 kN (120T),
for middle range loads, the underslung crane bridges have a capacity up to 125 kN (12.5T).
The crane bridge can be manufactured in hot rolled section or in box section.
reinforced with angles for topmounted crane only !
welded reconstructed sections
The construction of crane runways can be achieved by attachment to the main frames of the buiding or by mounting on independent columns.
For topmounted crane, they are made of two longitudinal beams (Ishape or boxshape) on which are fixed the rails where the wheels of the crane circulate. In this case, the runways are controlled under torsion effect due to the eccentricity of the vertical and horizontal loads. Some reinforcement can be added to the top flange to prevent excessive torsion or deflection.
For underslung crane, they are also made of two longitudinal beams but the wheels circulate directly on the bottom flange of the beams. Here, additional checking like local bending are required for the bottom flange.
For monorail hoist block, the principle is the same as underslung crane but with only one longitudinal beam and no lateral load.
Extract of the standard §2.2.1 Classifications of actions  General
(l)P Actions induced by cranes shall be classified as variable and accidental actions which are represented by various models as described in 2.2.2 and 2.2.3.
Extract of the standard §2.2.2 Classifications of actions  Variable actions
(1) For normal service conditions, variable crane actions result from variation in time and location. They include gravity loads including hoist loads, inertial forces caused by acceleration/deceleration and by skewing and other dynamic effects.
(2) The variable crane actions should be separated into:
variable vertical crane actions caused by the selfweight of the crane and the hoist load;
variable horizontal crane actions caused by acceleration or deceleration or by skewing or other dynamic effects.
(3) The various representative values of variable crane actions are characteristic values composed of a static and a dynamic component.
(4) Dynamic components induced by vibration due to inertial and damping forces are in general accounted by dynamic factors φ to be applied to the static action values. (2.1) where:
F_{φ,k} is the characteristic value of a crane action;
φ_{i} is the dynamic factor, see Table 2.1;
F_{k} is the characteristic static component of a crane action.
(5) The various dynamic factors and their application are listed in Table 2.1.
(6) The simultaneity of the crane load components may be taken into account by considering groups of loads as identified in Table 2.2. Each of these groups of loads should be considered as defining one characteristic crane action for the combination with noncrane loads. NOTE: The grouping provides that only one horizontal crane action is considered at a time.
Table 2.1 Dynamic factors φ_{i}
Dynamic factors
Effects to be considered
To be applied to
φ_{1}
Excitation of the crane structure due to lifting the hoist load off the ground
selfweight of the crane
φ_{2}
Dynamic effects of transferring the hoist load from the ground to the crane
hoist load
φ_{3}
Dynamic effects of sudden release of the payload if for example grabs or magnets are used
hoist load
φ_{4}
Dynamic effects induced when the crane is travelling on rail tracks or runways
selfweight of the crane and hoist load
φ_{5}
Dynamic effects caused by drive forces
drive forces
φ_{6}
Dynamic effects of a test load moved by the drives in the way the crane is used
test load
φ_{7}
Dynamic elastic effects of impact on buffers
buffer loads
Table 2.2  Groups of loads and dynamic factors to be considered as one characteristic crane action
Symbol
Section
Groups of loads
Ultimate Limit State
Test load
Accidental
1
2
3
4
5
6
7
8
9
10
1
Selfweight of crane
Q_{c}
2.6
φ_{1}
φ_{1}
1
φ_{4}
φ_{4}
φ_{4}
1
φ_{1}
1
1
2
Hoist load
Q_{h}
2.6
φ_{2}
φ_{3}

φ_{4}
φ_{4}
φ_{4}
η^{(1)}

1
1
3
Acceleration of crane bridge
H_{L}, H_{T}
2.7
φ_{5}
φ_{5}
φ_{5}
φ_{5}



φ_{5}


4
Skewing of crane bridge
H_{S}
2.7




1





5
Acceleration or braking of crab or hoist block
H_{T3}
2.7





1




6
Inservice wind
F_{w}
Annex A
1
1
1
1
1


1


7
Test load
Q_{T}
2.10







φ_{6}


8
Buffer force
H_{B}
2.11








φ_{7}

9
Tilting force
H_{TA}
2.11









1
^{1} η is the proportion of the hoist load that remains when the payload is removed, but is not included in the selfweight of the crane.
Each of the crane bridge longitudinal positions (along the runway) and transversal positions (staggered or skewed wheels with respect to the rail axis) must be analyzed to detect maximum forces and deformations.
We have developed a specific mechanical solver to do exactly this job.
B2  Way geometry and section parameters B21  Runway element
B22  Cross section
Minimum steel grade of the elements : S275 (f_{y} = 275 MPa, E = 210000 MPa) Runway section : IPE360 Rail section : 50x30 (the rail is welded on the runway and the wear of the rail of 25% is taken into account in the calculations of the characteristics.)
Mechanical characteristics :
Area : A=91.6 cm^{2}
Shear areas :
on zz : : A_{sz}=42.7 cm^{2}
top flange on yy : A_{sy,top}=25.6 cm^{2}
bottom flange on yy : A_{sy,bot}=21.6 cm^{2}
Second moments of area :
about yy : I_{y}=21261.3 cm^{4}(with : : z_{G} = 21.7cm)
top flange about zz : I_{z}=1529.4 cm^{4}
bottom flange about zz : I_{z}=521.1 cm^{4}
Mechanical characteristics :
Area : A=84.0 cm^{2}
Shear areas :
on zz : : A_{sz}=35.1 cm^{2}
top flange on yy : A_{sy,top}=21.6 cm^{2}
bottom flange on yy : A_{sy,bot}=21.6 cm^{2}
Second moments of area :
about yy : I_{y}=19834.0 cm^{4}(with : : z_{G} = 20.6cm)
top flange about zz : I_{z}=544.5 cm^{4}
bottom flange about zz : I_{z}=521.1 cm^{4}
F1  Ultimate Limit StatesF11  Stresses and Von Mises criteria §6.2
EN199311 (6.1)
top flange
web top
bottom flange
flanges middle
Span
right above
left above
right below
left below
right
left
right above
left above
right below
left below
above
below
1
163.4MPa
110.3MPa
151.9MPa
101.2MPa
50.4MPa
91.9MPa
101.9MPa
87.4MPa
105.7MPa
91.4MPa
48.0MPa
73.0MPa
2
169.8MPa
120.6MPa
167.8MPa
122.6MPa
39.3MPa
81.6MPa
76.7MPa
58.6MPa
79.8MPa
61.1MPa
41.1MPa
54.8MPa
Table F11.a  Maximal Von Mises criteria by span for each of the twelve checking points.
top flange
web top
bottom flange
flanges middle
Span
right above
left above
right below
left below
right
left
right above
left above
right below
left below
above
below
1
0.594
0.401
0.552
0.368
0.183
0.334
0.371
0.318
0.385
0.332
0.174
0.265
2
0.618
0.439
0.61
0.446
0.143
0.297
0.279
0.213
0.29
0.222
0.15
0.199
Table F11.b  Maximal Von Mises ratio by span for each of the twelve checking points.
top flange
web top
bottom flange
flanges middle
right above
left above
right below
left below
right
left
right above
left above
right below
left below
above
below
Stress
8.4m
8.4m
8.4m
8.4m
6.0m
6.0m
2.1m
2.7m
2.1m
2.7m
2.1m
2.1m
ULSSTR
11
4
11
4
8
8
12
8
12
8
8
8
Crane
8.4m
8.4m
8.4m
8.4m
4.2m
4.2m
2.1m
0.9m
2.1m
0.9m
2.1m
2.1m
Table F11.c  Position of stress, ULS combination and position of crane for the maximal rate of each of the twelve control points.
F12  Transverse buckling of the flanges §6.3
EN199311 (6.60 + 6.61)
F121  Top flange
Combination for the maximal work rate: ULSSTR 11
Span
N_{Ed}
M_{z,Ed}
k_{c}
L_{cr,z}
λ_{f}
N_{cr,z}
k_{fl}
χ_{z}
C_{m,z}
k_{zz}
Ratio
Section position
Crane position
1
174.5kN
15.0m.kN
0.82
4.92m
0.995
1309.6kN
1.1
0.543
0.964
1.048
0.691
2.7m
2.7m
2
89.7kN
9.3m.kN
0.82
3.28m
1.018
1049.0kN
1.102
0.529
0.971
1.022
0.681
8.4m
8.4m
Table F121  Maximal buckling ratio by span for top flange.
F122  Bottom flange
Combination for the maximal work rate: ULSSTR 12
Span
N_{Ed}
M_{z,Ed}
k_{c}
L_{cr,z}
λ_{f}
N_{cr,z}
k_{fl}
χ_{z}
C_{m,z}
k_{zz}
Ratio
Section position
Crane position
1
135.2kN
1.9m.kN
0.91
5.46m
1.466
362.3kN
1.147
0.326
0.935
1.086
0.585
6.0m
2.4m
2
134.4kN
1.9m.kN
0.752
3.008m
0.808
1194.0kN
1.081
0.657
0.959
1.042
0.358
6.0m
2.4m
Table F122  Maximal buckling rate by span for bottom flange.
F13  Local buckling §6.6 F131  Local buckling of the flanges EN199315 §4
EN199315 (4.14) Combinations for the maximal work rates: ULSSTR 8 (top flange), ULSSTR 8 (bottom flange)
top flange
bottom flange
Span
M_{y}
W_{el,y}
Ratio
Section position
Crane position
M_{y}
W_{el,y}
Ratio
Section position
Crane position
1
71.1m.kN
1288.1cm^{3}
0.202
2.1m
2.1m
36.3m.kN
977.8cm^{3}
0.136
5.7m
2.1m
2
40.0m.kN
1121.3cm^{3}
0.131
8.6m
6.8m
49.9m.kN
964.6cm^{3}
0.188
6.2m
2.4m
Table F131  Maximal local buckling ratio by span for each flange.
F132  Local buckling of the web under shear EN199315 §5
EN199315 (5.10) Combination for the maximal work rate: ULSSTR 1
Span
k_{τ}
h_{w}/t_{w}
lim_{max}
σ_{E}
τ_{cr}
λ_{rel,w}
χ_{w}
Ratio
Section position
Crane position
1
5.352
41.825
66.299
h_{w}/t_{w} < lim_{max} : La vérification n'est pas nécessaire
2
5.368
41.825
66.395
h_{w}/t_{w} < lim_{max} : La vérification n'est pas nécessaire
Table F132  Maximal local buckling ratio by span for the web under shear.
F133  Local buckling of the web under point load EN199315 §6
EN199315 (6.14) Combination for the maximal work rate: ULSSTR 1
Span
F_{Ed;}
s_{s}
F_{cr}
λ_{rel,F}
χ_{F}
L_{eff}
Ratio
Section position
Crane position
1
41.4kN
0.075m
1737.0kN
0.563
0.888
0.222m
0.085
5.7m
3.9m
2
41.4kN
0.075m
1739.3kN
0.563
0.888
0.223m
0.085
7.0m
5.1m
Table F133  Maximal local buckling ratio by span for the top of the web under point load.
F134  Interactions EN199315 §7
EN199315 (7.2) Combination for the maximal work rate: ULSSTR 8
Span
η_{2}
η_{1}
Ratio
Section position
Crane position
1
0.085
0.202
0.246
2.1m
2.1m
2
0.085
0.131
0.189
8.6m
6.8m
Table F134.a  Maximal local buckling interaction ratio by span under point load.
si EN199315 (7.1) Combinations for the maximal work rates: ULSSTR 1 (top flange), ULSSTR 1 (bottom flange)
top flange
bottom flange
Span
η_{3}
W_{f,Rd}
W_{pl,Rd}
η_{1}
Ratio
Section position
Crane position
η_{1}
Ratio
Section position
Crane position
1
0.0
η_{3} ≤ 0.5 : La vérification n'est pas nécessaire
2
0.0
η_{3} ≤ 0.5 : La vérification n'est pas nécessaire
Table F134.b  Maximal local buckling interaction ratio by span under shear.
F2  Serviceability Limit States
Limiting values of horizontal deflections (EN19936 7.1) : L/600
Limiting values of vertical deflections (EN19936 7.2) : L/600
Limiting values for web breathing (EN19936 §7.4(3)) : b/t_{w} < 120
Limiting values for vibration of the bottom flange (EN19936 §7.6(2)) : L_{f} / i_{f,z} ⩽ 250
Combinations for the maximal deflection rates: SLS 6 (vertical), SLS 4 (horizontal)
SLS _{z}
SLS _{y}
Web breathing
Vibration of the bottom flange
Span
Abscissa
Ratio
Abscissa
Ratio
Ratio
Ratio
1
2.7m
0.378
3.0m
0.843
0.349
0.56
2
8.2m
0.16
8.2m
0.89
0.349
0.373
Table F2  Maximal SLS ratios and associate positions by span for each axis.