For the design of conductors, equipment and supports including foundations, ultimate limit state shall be determined by consideration of the load case giving the maximum load effect in each individual element.
Conductor tensile forces shall be determined according to the loads acting on the conductors in the load case under consideration. The components of the conductor tensile forces at the attachment points of the support including the effect of vertical and horizontal angles shall be taken into account properly. The loads on the supports shall be selected taking into account the defined function of the support in the overhead contact line system. Where a support carries out several functions, e.g. a tensioning structure carrying as well cantilevers, the most unfavourable combination of the loads that can occur simultaneously shall apply.
The purchaser specification may give additional requirements, if necessary. Short-term load conditions occurring during installation and re-construction activities shall be separately considered.
The standard load cases are defined in 6.3.1.2 to 6.3.1.7. The applications of these load cases are shown in Table 14 and 6.3.2.
There are relations between environmental conditions like temperature and wind velocity.
6.3.1.2 Load case A: Loads at minimum temperature
Permanent loads, conductor tensile forces at the minimum and design ambient temperature shall be considered.
The temperature conditions described in 6.2.7 should be considered.
6.3.1.3 Load case B: Maximum wind loads
Permanent loads, conductor tensile forces increased by the action of wind and wind loads on each element according to 6.2.4 of this standard, acting in the most unfavourable direction.
The ambient temperature under this condition should be as specified in 6.2.7.
6.3.1.4 Load case C: Ice loads
Permanent loads, conductor forces increased by the ice loads according to 6.2.5 and ice loads on structures, if applicable.
6.3.1.5 Load case D: Combined action of wind and ice loads
Permanent loads, conductor tensile forces increased by the combined effect of ice loads and wind loads, according to 6.2.6 of this standard, and wind and ice loads acting on structures.
The wind load acts in the most unfavourable direction.
6.3.1.6 Load case E: Construction and maintenance loads
Permanent loads, increased by construction and maintenance loads according to 6.2.8 of this standard together with a reduced wind load and reduced ice load where specified.
6.3.1.7 Load case F: Accidental loads
Permanent loads together with the unintentional reduction of one or several conductor forces.
6.3.2 Type of structures and application of load cases 6.3.2.1 Cantilevers
Cantilevers carry the overhead contact line of one or more tracks. They may be fixed to the supports by hinges allowing the cantilevers to rotate around a vertical axis, providing no resistance to longitudinal loads from the overhead contact line. Alternatively, cantilevers fixed rigidly to the structures offer resistance against longitudinal forces created by the overhead contact lines.
The relevant load cases are:
– A, B, C and if necessary D for hinged cantilevers,
– A, B, C, if necessary D, if necessary E and F for rigid cantilevers.
6.3.2.2 Head spans
Head spans carry overhead contact lines by means of rope elements and insulators under tensile load only.
The relevant load cases are A, B, C, if necessary D, if necessary E and F. The load case F is applicable only for head spans with midpoints.
6.3.2.3 Rigid cross-span structures (cross-beams, portals)
Rigid cross-span structures consist of bending resistant beams which are fixed onto the structures either by hinges or by bending resistant joints.
The relevant load cases are A, B, C, if necessary D, if necessary E and F.
6.3.2.4 Suspension structures
A suspension structure carries one or several cantilevers to support the overhead contact line.
The relevant load cases are A, B, C, if necessary D and if necessary E.
6.3.2.5 Curve pull-off structures
Curve pull-off structures carry radial forces from one or several overhead contact lines, and sometimes vertical loads (e.g. when cants and/or slopes exist).
The relevant load cases are A, B, C, if necessary D and if necessary E.
6.3.2.6 Midpoint anchor structures
A midpoint anchor structure is designed to resist the termination forces of the midpoint anchor in addition to other functions such as carrying cantilevers.
The relevant load cases are A, B, C, if necessary D, if necessary E and F.
6.3.2.7 Midpoint structures
A midpoint structure is designed to resist the radial forces from the midpoint anchors in addition to the other functions such as carrying the cantilevers.
The relevant load cases are A, B, C, if necessary D and if necessary E.
6.3.2.8 Structures for flexible and rigid cross-supporting structures
Structures designed to resist the forces resulting from any kind of cross-supporting structures such as head spans, cross-beams and cross-spans.
The relevant load cases are A, B, C, if necessary D and if necessary E. Load case F shall be considered if a midpoint is arranged there.
6.3.2.9 Structures for horizontal catenary wire arrangements
At structures for horizontal catenary wire arrangements forces act in several directions and at different heights simultaneously.
The relevant load cases are A, B, C, if necessary D and F.
NOTE A horizontal catenary wire is an arrangement where the contact wires are supported from wires that are mainly in a horizontal position. This arrangement is mainly used within urban areas. The masts or buildings where the horizontal wires are fixed can be relatively far from the tracks.
6.3.2.10 Tensioning structures
A tensioning structure carries the termination of overhead contact line equipment and other conductors being automatically tensioned or rigidly fixed and may also have other functions such as carrying cantilevers or head span elements.
The relevant load cases are A, B, C, if necessary D and if necessary E.
Load case F if contact lines are terminated in two opposing directions in order to allow for the unintentional reduction of tensile loads.
6.3.2.11 Structures with feeder and parallel reinforcing lines
These structures carry the loads from feeders and parallel reinforcing lines and perform other functions within the overhead contact line installation. If necessary a distinction should be made between structures fitted with suspension or tension insulator sets.
The relevant load cases are A, B, C, if necessary D, if necessary E and F.
6.3.2.12 Overhead contact line structures carrying additional overhead power lines Structures with additional overhead power lines carry the loads from overhead lines and take care of other functions within the overhead contact line installation.
The relevant load cases are A, B, C, if necessary D, if necessary E and F concerning the actions resulting from the overhead contact line. In addition the load cases according to EN 50341-1 in Europe have to be considered with respect to the function of the support within the overhead contact line system.
6.3.2.13 Anchor supports
Anchor supports are structural elements to resist the tensile forces of stay wires supporting structures of contact lines.
The load cases shall be selected according to the type of anchored structure.
6.3.2.14 Support foundations
Foundations shall be considered in accordance with 6.5. The relevant load cases are A, B, C, if necessary D, if necessary E and F.
Table 14 – Summary of load cases to be considered for each type of structures
Type of structure Load case to be considered
Minimum A temperaturef
WindB g C Icee, h
Wind D iceand e, h
Construction and E maintenance e, h
AccidentalF g
1a Cantilevers hinged X X X X X -
1b Cantilevers rigid X X X X X X
2 Headspans X X X X X X a
3 Portals/ Cross-beams X X X X X X
4 Suspension structures X X X X X -
5 Pull-off structures X X X X X -
6 Midpoint anchor X X X X X X
7 Midpoint structures X X X X X -
8 Structures for flexible
and rigid cross-supports X X X X X X a
9 Structures for horizontal catenary wire
arrangements X X X X - X
10 Tensioning structures X X X X X X c
11 Structures with feeder and parallel reinforcing
lines X X X X X X e
12 OCS structures carrying
additional power lines b X X X X X X
13 Anchor supports X d X d X d X d X d X d
14 Support foundations X X X X X X
The above is provided as a guide. For some structures additional load combinations will be necessary.
a If midpoint.
b See also EN 50341-1 in Europe.
c If contact lines are terminated in two opposite directions.
d Depending on the type of anchor.
e If necessary.
f Minimum temperature to be considered with no other climatic action. See 6.2.7.
g The normal ambient reference temperature to be assumed for the extreme wind load condition. See 6.2.7.
h Temperature to be assumed with ice loads and combined wind and ice load, where relevant. See 6.2.7.
6.3.3 Partial factors for actions 6.3.3.1 General
The use of factors is standard practice according to ISO 10721 (all parts) and EN 1993 (all parts) in Europe for steel structures and to EN 1992 (all parts) in Europe for concrete structures. The partial factors are separated into partial factors for actions and partial factors for materials. The relevant partial factors for actions and for materials are specified in this standard. For conditions not covered here, partial factors may be taken from ISO 2394 and EN 1990 in European Standards for structural design or may be given in the purchaser specification. The applicable partial factors are summarized in Table 15 or can be defined in national regulations.
6.3.3.2 Permanent actions
The partial factor for permanent actions of self-weight is γG and for permanent actions of conductor tensile forces is γCG. A value of 1,3 is recommended; alternative values may be given in the purchaser specification. Where the self-weight of any element acts favourably, i.e.
reducing the loading, the partial factor γG shall be assumed to be 1,0.
6.3.3.3 Variable actions, wind and ice loads
For the partial factors γW for wind loads, γI for ice loads and γCV for conductor tensile forces under the action of wind or ice loads; a value of 1,3 is recommended. Alternative values may be given in the purchaser specification.
6.3.3.4 Accidental loads
In case of accidental load cases the partial factors γG for permanent loads, γC for conductor tensile forces and γA for accidental loads can be assumed as 1,0.
Dynamic loads due to wire breaking can be considered by the use of equivalent static loads.
6.3.3.5 Construction and maintenance loads
The partial factor for construction and maintenance loads γP shall be 1,5. This shall be combined with a value of 1,3 for partial factors γG and γCG for permanent actions.
Table 15 – Summary of partial factors for actions
Type of load Load case
A B C D E F
Permanent γGγCG 1,3 b 1,3 b 1,3 b 1,3 b 1,3 b 1,0 b
Permanent favourable γG, γCG 1,0 / 0 a 1,0 / 0 a 1,0 / 0 a 1,0 / 0 a 1,0 / 0 a 1,0 / 0 a
Wind γw, γCV - 1,3 b - 1,3 b - 1,0 b
Ice γI, γCV - - 1,3 b 1,3 b - -
Accidental γA - - - - - 1,0
Construction γP - - - - 1,5 -
a Equipment removed.
b Recommended value.