Info

Seismic action

Accidental actions

Rail traffic

b

b

Road traffic

b

Severance of overhead line

b

a If the self-weight is based on the final design, a value of 1.2 may be taken for steel bridges, if agreed with the relevant authority. b Accidental action Ad (design value).

Annex H (informative)

Dynamic analysis where there is a risk of resonance or excessive vibrations of railway structures: basis of the supplementary calculations

H.1 General

Annex H may be used as the basis of the supplementary calculations unless otherwise specified by the relevant authority.

Subject to agreement with the relevant authority, the simplified method given in H.2, H.3 and H.4 may be used for dynamic analysis, where:

— 220 km/h < v < 350 km/h, and/or the natural frequency is outside the limits in Figure 6.9 of ENV 1991-3:1995; and

— the bridge is simply supported with a skew less than 20°.

The simplified method only covers structural members where the direction of travel of the train is parallel to the longitudinal axis of the member and where the influence line for deflection is equal to the span of the member. NOTE More precise methods are currently undergoing development by the International Union of Railways (UIC)1^.

H.2 Deck acceleration

H.2.1 Additional check for deck acceleration at value of k (kmax) corresponding to 1.2 X maximum line speed

2k e

< 0.35g where k e is given by 0.9kmax # ke # 1.1kmax, and chosen to give the minimum upper limit of Adeck;

cos (p/2ke) is taken as positive.

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