Columns, trestles, bearings, articulations, tension anchors as well as for the calculation of contact pressures under bearings.

determinant length of the supported members

6.4.3.4 Reduced dynamic effects

(1) In the case of arch bridges and concrete bridges of all types with a cover of more than 1,00 m, <J>2, <J>3 may be reduced as follows:

where:

h in [m] is the height of cover including the ballast to the top of the sleeper, (for arch bridges, to the crown of the extrados).

(2) Columns with a slenderness (buckling length/radius of gyration) < 30, abutments, foundations, retaining walls and ground pressures may be calculated without taking into account dynamic effects.

6.4.4 Dynamic effects when there is a risk of resonance or excessive vibration of the structure

(1)P Where the characteristics of the structure are such that it is not within the limits specified in Figure 6.9, or if the traffic speed is greater than [220] km/h, there is a risk that resonance or excessive vibration of the deck may occur (with an exceedance of authorized accelerations, end rotation of structure, deck twist, etc.).

These dynamic effects are not covered by the dynamic factors specified in 6.4.3.2(1 )P and further detailed calculations shall be made.

Note: Indications for such calculations are given in annex H.

6.5 Horizontal forces - characteristic values 6.5.1 Centrifugal forces

(1)P Where the track on a bridge is curved over the whole or part of its length, the centrifugal force and the track cant shall be taken into account.

(2)P The centrifugal forces shall be taken to act outwards in a horizontal direction at a height of 1,80 m above the running surface (see Figure 1.1).

(3)P The calculations shall be based on the maximum speed compatible with the layout of the line. In the case of Load Models SW a speed of 80 km/h shall be assumed.

(4)P The characteristic value of the centrifugal force shall be determined according to the following equation:

where:

Quo Qtk characteristic values of the centrifugal forces in [kN, kN/m]

Qvk. Qvk characteristic values of the vertical loads specified in 6.3.

f reduction factor (see below)

v maximum speed specified in [m/s]

V maximum speed specified in [km/h]

g acceleration due to gravity [9,81 m/s2]

r radius of curvature in [m]

In the case of a curve of varying radii, suitable mean values may be taken for the value r.

(5)P The centrifugal force shall always be combined with the vertical load. The centrifugal force shall not be multiplied by the dynamic factor fa or <|>3.

(6)P For Load Model 71 and projected speeds higher than 120 km/h, two cases shall be considered:

(a) Load Model 71 with its dynamic factor and the centrifugal force for V = 120 km/h according to equation 6.5 with 1.

(b) A reduced Load Model 71 (fx Qvlc, fx q^) and the centrifugal force according to equation 6.5 for the maximum speed V specified, with a value for the reduction factor f.

where:

is the influence length in [m] of the loaded part of curved track on the bridge, which is most unfavourable for the design of the structural elements under consideration.

is the maximum speed specified for V z 120 km/h or L, s 2,88 m for 120 km/h <V s 300 km/h ) (see Table 6.3 or Figure 6.10)) /(V0 = f{300) for V >300 km/h. )

Mm] |
Maximum speed of the line in [km/h] | ||||

¿120 |
Was this article helpful? |

## Post a comment