The main difference between the configurations of these hoisting devices is the working load limit (WLL); see also «lifting point». From commercially catalogues of crane bridge 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).
reinforced with angles for topmounted crane only !
welded reconstructed sections
The crane runways can be fixed to the main frames of the buiding or mounted 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 parametersB21  Runway element
B22  Cross section
Minimum steel grade of the elements : S275 (f_{y} = 275 MPa, E = 210000 MPa) Runway section : HEA300 Rail section : 40x30 (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=121.5 cm^{2}
Shear areas :
on zz : : A_{sz}=37.3 cm^{2}
top flange on yy : A_{sy,top}=42.0 cm^{2}
bottom flange on yy : A_{sy,bot}=42.0 cm^{2}
Second moments of area :
about yy : I_{y}=20301.8 cm^{4}(with : : z_{G} = 15.7cm)
top flange about zz : I_{z}=3166.2 cm^{4}
bottom flange about zz : I_{z}=3154.2 cm^{4}
Second moment of area, about its horizontal centroidal axis, of the combined cross section comprising the rail and a flange with an effective width of b_{eff} : I_{rf}=21.8 cm^{4}
Torsion constant of the flange (including the rail if it is rigidly fixed) : I_{t}=75.4 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
195.4MPa
181.8MPa
187.9MPa
174.7MPa
61.4MPa
130.3MPa
108.4MPa
108.4MPa
116.8MPa
116.8MPa
81.7MPa
95.7MPa
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
0.711
0.661
0.683
0.635
0.223
0.474
0.394
0.394
0.425
0.425
0.297
0.348
Table F11.b  Maximal Von Mises ratio by span for each of the twelve checking points.
F12  Transverse buckling of the flanges §6.3
EN199311 (6.60 + 6.61)
F121  Top flange
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
395.6kN
26.1m.kN
0.86
5.16m
0.808
2464.7kN
1.081
0.657
0.969
1.094
0.837
2.7m
2.7m
Table F121  Maximal buckling ratio by span for top flange.
F13  Local buckling §6.6F131  Local buckling of the flanges EN199315 §4
EN199315 (4.14)
top flange
Span
M_{y}
W_{el,y}
Ratio
Section position
Crane position
1
124.1m.kN
1699.9cm^{3}
0.266
3.6m
0.9m
Table F131  Maximal local buckling ratio by span for each flange.
F132  Local buckling of the web under shear EN199315 §5
EN199315 (5.10)
Span
k_{τ}
h_{w}/t_{w}
lim_{max}
σ_{E}
τ_{cr}
λ_{rel,w}
χ_{w}
Ratio
Section position
Crane position
1
5.348
30.824
66.269
h_{w}/t_{w} < lim_{max} : Verification is not needed
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)
Span
F_{Ed;}
s_{s}
F_{cr}
λ_{rel,F}
χ_{F}
L;_{eff}
Ratio
Section position
Crane position
1
65.9kN
0.127m
2659.8kN
0.544
0.919
0.31m
0.091
3.3m
0.6m
Table F133  Maximal local buckling ratio by span for the top of the web under point load.
F134  Interactions EN199315 §7
EN199315 (7.2)
Span
η_{2}
η_{1}
Ratio
Section position
Crane position
1
0.091
0.266
0.303
3.6m
0.9m
Table F134.a  Maximal local buckling interaction ratio by span under point load.
si EN199315 (7.1)
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 : Verification is not needed
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
SLS _{z}
SLS _{y}
Web breathing
Vibration of the bottom flange
Span
Abscissa
Ratio
Abscissa
Ratio
Ratio
Ratio
1
3.0m
0.799
3.0m
0.798
0.257
0.301
Table F2  Maximal SLS ratios and associate positions by span for each axis.