The internal forces and moments within cross-span supports and structures as described in 6.3.2 shall be determined using the principles of static of rigid and flexible structures whether being statically determinate or statically indeterminate structures or flexible rope systems.
Additional requirements can be found in
– ISO 10721 (all parts) and EN 1993 (all parts) and EN 1090-1 (in Europe) for steel structures,
– EN 12510 (in Europe) for timber structures, – EN 12843 (in Europe) for concrete poles,
– EN 1992 (all parts) (in Europe) for concrete structures, – ISO/TR 11069 and EN 1999 (all parts) (in Europe),
– EN 50341-1 (in Europe),
– the recognised publications of structural analysis.
6.4.2 Analysis of resistance
The elements of cross-span supports of contact line installations are loaded in compression, tension, bending or torsion. The calculation of the resistance of elements shall consider the type of load as well as buckling, stability if required and the analysis of connections.
Concerning the analysis of resistance of steel structures, reference shall be made to EN 50341-1 (in Europe) and to:
– ISO 10721 (all parts), ISO 630 (all parts) and EN 1993-1-1 (in Europe) for steel structures, – EN 12510 (in Europe) for timber structures,
– In Europe to EN 1992-1-1 and EN 12843 for reinforced concrete structures.
The resistance of solid wires, stranded conductors of metallic material loaded by tensile forces follow from the relevant standards, e.g. EN 50149 or EN 50182 in Europe. The design resistance shall be obtained by dividing the failing load by a material partial factor.
6.4.3 Material partial factors
The partial factors γM for steel material may be taken either from standard values, for example from ISO 10721 (all parts), ISO 630 (all parts), EN 1993-1-1 or EN 50341-1 in Europe or from the recommended values in Table 16. Alternative values can be found in national regulations.
Table 16 – Recommended values for partial factors γM for steel material
Structure type γM
Resistance of cross-sections under tensile forces
and bending 1,10
Resistance of members to buckling 1,10
Resistance of connections under shearing and
bearing 1,25
Resistance of net cross-sections based on ultimate
tensile stress under tensile load 1,25
Resistance of welded connections 1,25
Resistance of bolts in tension 1,25
Metallic ropes under tensile force 1,50
The partial factors for timber structures shall be taken as γM = 1,50, for the resistance of cross- sections and elements.
The partial factors for concrete structures may be taken from the recommended values in Table 17. Alternative values can be found in national regulations.
Table 17 – Recommended values for partial factors γM for concrete structures
Structure type γM
Pre-stressing force a 0,90 or 1,20
Concrete 1,50
Reinforcing steel (ordinary or pre-stressed) 1,15
a Depending upon whether the action is favourable or not for the calculated effect.
Tensile stresses in the concrete of pre-stressed concrete poles are not permitted under the following conditions:
– 66 % of the sum of permanent and variable loads;
– sum of permanent and 40 % of variable loads.
EN 12843 should be applied in Europe to precast concrete masts and poles.
6.4.4 Verification of resistance
The verification of resistance shall demonstrate that the resistance taking into account the relevant material and structure behaviour partial factors is higher than the effects of action with their relevant partial factors applied.
6.4.5 Verification of serviceability
In general, the deformation of supports and all other structural components shall be kept in permissible limits to guarantee the serviceability of the overhead contact line. Detailed requirements should be given in the purchaser specification.
The deformation can be calculated using the methods of static analysis as described in 6.4.1.
In some cases e.g. on bridges, displacement due to vibration has to be taken in account.
Types of tolerances and limits are given in Table 12.
6.4.6 Material for structures
Concerning suitable materials, reference shall be made to national regulations or to the following standards:
– steel materials and welding consumables shall comply with the requirements of ISO 10721 (all parts), ISO 630 (all parts) and EN 1993-1-1 and EN 1993-1-10 in Europe as well as EN 10025 (all parts), EN 10149 (all parts) and EN 10164 in Europe. Structural steel qualities S235J0, S235J2G3/G4, S355J0 and S355J2G3/G4 according to EN 10025 (all parts) in Europe or equivalent qualities are preferred. Only the strength qualities 4.6, 5.6, 8.8 and 10.9 according to ISO 898-1 should be used for bolts (and 5 and 8 according to ISO 898-2 and EN 20898-2 in Europe for nuts). Appropriate consideration shall be given to minimum service temperatures, material thicknesses, tensile stresses and the requirements for the avoidance of brittle fracture,
– structural parts made of aluminium or aluminium alloys shall comply with ISO/TR 11069:1995 and EN 1999 (all parts) in Europe. The standards EN 755-1 and EN 755-2 for extruded tubes and profiles made of aluminium and EN 485-1 for sheets, strips and plates made of aluminium shall also be considered in Europe,
– EN 50182 for stranded conductors made of aluminium, aluminium alloy and composite conductors in Europe,
– EN 50345 for synthetic ropes in Europe,
– concrete structures for new foundation should comply in Europe with EN 1992-1 (all parts).
Where different steel qualities are proposed, the performance at low temperatures should be considered, for example through the use of impact testing or by long-term experience.
NOTE On this basis steel quality S235JR is currently used in some countries.
Timber structures should be specified in conformity with the requirements of EN 12465, EN 12479, EN 12509, EN 12510 and EN 12511 in Europe.
EN 10210 (all parts) or EN 10219 (all parts) shall be used in Europe for hollow sections.
Additionally guidance may be given in a purchaser specification. Guidance on the design of structural details can also be found in Annex B and in EN 1090 (all parts) for steel and aluminium for Europe.
6.4.7 Corrosion protection and finishes
Cross-span supports and structures shall be designed to fulfil their intended working life. To ensure their longevity, steel components shall be protected against corrosion. Copper, copper alloy and aluminium components do not always require protection, due to their material properties. Plastic components do not corrode but their longevity in service will need to be assured.
Galvanizing of steel parts is standard practice as described in ISO 1461. In addition, a paint coating over galvanizing applied in plant (Duplex system) can be recommended, subject to earthing and bonding considerations. The coating material should be lead-free and in accordance to national labour safety regulations. Moreover, the guidelines established by operators should be applied accordingly.
Generally it is presupposed that the execution of work is carried out with the necessary skill and adequate equipment. The execution of steel and aluminium structures should comply to EN 1090 (all parts) for Europe.