Figure 6.18: Design situation II - equivalent load

Note: The above-mentioned equivalent load is only to be considered for determining the ultimate strength or the stability of the structure as a whole. Edge beams, brackets, etc, need not to be designed for this load.

(4)P Design situations I and II shall be examined separately. A combination of these loads shall not be considered.

(5)P For structural elements which are situated above the rail level measures to avoid damage shall be agreed.

Note: These measures shall be agreed with the relevant authority. Derailment under structures

(1)P When derailment occurs, there is a risk of collision between derailed vehicles and structures adjacent to the track. The requirements for collision loading and other design requirements shall be specified

Note: These requirements shall be specified in agreement with the relevant authority.

6.7.2 Accidental action due to the severance of overhead line equipment

(1)P The force imposed on the structure as a consequence of the rupture of a catenary shall be considered as a static force acting in the direction of the intact part of the catenary. This accidental force shall be taken into consideration with a design value of 20 kN.

It shall be assumed that for.

1 track 1 catenary and contact wire

2 - 6 tracks 2 catenaries and contact wires more than 6 tracks 3 catenaries and contact wires may break simultaneously.

(2)P The wires considered broken shall be those which give the most unfavourable load effects.

6.7.3 Accidental actions from road traffic

(1)P Accidental actions due to road vehicles are defined in 4.7.2.

(2)P With regard collisions on decks, it must be considered that railway bridges are in many cases much more sensitive to collision than road bridges.

Note: The specified vehicle collision force and its relation to vertical clearance and other form of protection are taken as defined or agreed by the relevant authority.

6.8 Assessment of traffic loads on railway bridges 6.8.1 General

(1)P Each structure shall be designed for the greatest number of tracks geometrically and structurally possible in the least favourable position, irrespective of the position of existing tracks.

Note: The minimum spacing between centre-lines of the tracks shall be specified by the relevant authority.

(2)P All action effects shall be determined with the loads and forces placed in the most unfavourable positions. Actions which produce a relieving effect shall be neglected (except for Load Models SW, with which actions which have relieving effects may be taken in account).

(3)P All continuous beam bridges designed for Load Model 71 shall be checked additionally for Load Model SW/O. The factor a is applied to Load Model SW/O and to Load Model 71.

(4)P For structures carrying one, two or more tracks all relevant actions shall be applied according to Table 6.5.

Table 6.5: Summary of loads on bridges depending on number of tracks of a bridge

Number of tracks on a bridge

Case a1>

il loads Case b1>

Heavy loads if specified

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