Info

gr«

[0,80]

[1,00]

•y

[0]

Wind Forces2'

Fwk or F^ F **

[0,6] [1,00]

[0,6]

[0,5]

[0]

Temperature Effect

x3) 1 k

[0,6]

[0,8]

[0,6]

[0,5]3)

[0r8] if one track loaded [0,6] if two tracks loaded

[0,4] if three or more tracks are simultaneously loaded

Whenever wind action is required to be considered with traffic, the wind action ♦o or ♦o Fwh should be taken as no greater than Fw" (see ENV 1991-2.4)

If deflection is being considered, see 6.8.1 (5)P and G.3.1

G.3 Serviceability limit states

G.3.1 Performance criteria regarding deformations and vibrations G.3.1.1 General

(1) This clause G.3.1 specifies the limits of deformation to be considered in the design of new bridges.

Excessive bridge deformations can endanger traffic by creating unacceptable changes in track geometry and excessive vibrations in bridge structures. These may affect the load imposed on the bridge, and create conditions which cause passenger discomfort.

(2)P Checks on bridge deformations are required for the following conditions:

- for safety purposes (to confirm the stability and continuity of the track and to ensure that rail/wheel contact is maintained):

. vertical accelerations of the deck, . twist of the deck, . rotation at the ends of the deck, . change of horizontal angle,

- for passenger comfort:

. vertical deflections of the deck.

(3)P It is also necessary to ensure that any deformations remain within the elastic limits of the materials used.

(4) The limits given in this clause G.3.1 take into account the fact that some action effects are compensated by track maintenance (for instance: settlement of foundations, creep effect, ).

(5) Designers will have to pay special attention to temporary bridges because of the flexibility and elasticity of this kind of structures.

Note: The relevant authority may give special specifications for these temporary bridges depending upon the conditions in which they are used (e.g. skew bridges).

G.3.1.2 Limit states for traffic safety G.3.1.2.1 Vertical acceleration of the deck

(1)P These checks are required for speeds V> [220] km/h or when the natural frequency of the structure is not within the limits shown in Figure 6.9.

Note: They shall be made for the actual traffic as defined in annex H.

(2) A limiting value of 0,35g for vibrations up to 20 Hz should be taken for decks with ballasted tracks unless otherwise specified.

Note: The relevant authority may specify a different limiting value.

(3) Where V <; [220] km/h and the natural frequency of the structure is within the limits shown in Figure 6.9, the risk of excessive acceleration is covered.

Note: Nevertheless for some values of deflection excessive accelerations can occur. As a first approach it is recommended that the limits of deflection given in table G.5 should be satisfied.

G.3.1.2.2 Deck twist

(1)P The twist of the bridge deck is to be calculated taking into account the characteristic values of Load Model 71 multiplied by

(2)P The maximum twist measured over a length of 3m shall not exceed the following values:

(3)P For speeds V > [220] km/h an additional check is required to ensure that t i. [1,2] mm/3m for actual traffic loading, multiplied by the relevant dynamic factor.

V * 120 km/h t z [4,5] mm/3m 120 < V <: [220] km/h t * [3,0] mm/3m

Figure G.1: Permissible deck twist

Note: Unless otherwise specified, the total twist due to any twist which may be present in the track when the bridge is unloaded (say in a transition curve), and that due to the total deformation of the bridge, shall not exceed [7,5] mm/3m.

G.3.1.2.3 Rotations at the end of the deck (for ballasted tracks)

(1)P Under the characteristic value of Load Model 71, multiplied by the dynamic factor $ and temperature differentials the maximum angular rotations at the ends of the deck measured on the axis of the track shall not exceed the following:

a) for single track bridges

0 = [6,5 x 10"3 radians] for transition between the deck )

and the embankment )(G-2)

6, + 02 = [10 x 10"3 radians] between two consecutive decks )

b) for double track bridges

0 = [3,5 x 10"3 radians] for transition between the deck )

and the embankment )(G-3)

01 + 02 = [5 x 10"3 radians] between two consecutive decks. )

(2)P For speeds V > [220] km/h the following additional check is required for actual traffic loads, multiplied by the relevant dynamic factor.

2 x 10*3 for transition between the deck )

01 + 02 = [- radians] between two consecutive decks )

hw where:

h{m) is the distance between the rail and the centre of the bridge bearing.

Figure G.2: Angular rotations at the end of the decks

G.3.1.2.4 Horizontal deflections of the deck

(1)P This condition shall be checked for: Load Model 71 multiplied by the dynamic factor 4>, wind loads, nosing force, centrifugal forces and the effect of temperature differentials between the two sides of the bridge together.

(2)P The horizontal deflection 6h of the deck shall not produce:

- an angular variation greater than the values given in the following table, or

- a radius of horizontal curvature less than the values in the following table G.3.

Table G.3: Maximum angular variation and minimum radius of curvature

Speed range

(km/h)

Maximum angular variation

Minimum radius of curvature

Single deck

multi-deck bridge

V s [120] [120] < V s [220] [220] < V

[0,0035] rd [0,0020] rd [0,0015] rd

[1700]m [6000]m [14000]m

[3500]m [9500]m [17500]m

(3) The radius of curvature is given by:

Note: The horizontal deformation includes the deformation of the bridge deck and the substructure (including piers, piles and foundations).

G.3.1.3 Limiting values for the maximum vertical deflection for passenger comfort

Note: The limiting values for the vertical deflections are provisional subject to the conclusions of current research work which is not yet completed.

(1) To ensure passenger comfort, limiting values are given in this clause for the maximum vertical deflection of railway bridges as a function of the span length L and the train speed V. Limiting values for deformations for reasons of safety are given in clause G.3.1.2.

(2) The comfort of the passengers depends on the vertical acceleration 6V inside the coach during travel. Levels of comfort are classified as shown in the Table G.4 below:

Table G.4

Level of comfort

Vertical acceleration 6V

very good

1,0 m/s2

good

1,3 m/s2

acceptable

2,0 m/s2

Note: The relevant authority may specify for their lines the level of comfort or the limiting values for the vertical acceleration.

(3)P The vertical deflections shall be determined at the centre line of the track due to traffic loading given in clause 6.8.1(5)P and 6.8.1(6)P.

(4) The limiting value 6/L given in Figures G.3, G.4 and Table G.5 for the maximum vertical deflection apply to the "very good" level of comfort with />„ = 1,0 m/s2. For other levels of comfort (i.e. other accelerations b\) these limiting values may be adjusted by multiplication by acceleration b\ [m/s2].

(5) Deflections should not exceed [L/600].

(6)P The vertical radius of the track over the loaded structure must not be less than that laid down for the line.

(7)P The limiting values 6IL apply to both successive simply supported structures (Figure G.3 and Table G.5) and to continuous structures (Figure G.4 and Table G.5 multiplied by a factor 1,1) with three or more spans. Where the structure consists of fewer spans, the limiting values shall be increased by the factors given below:

- for 1 span structure, by a factor 2,0

- for 2 span structure, by a factor 1,5.

(8)P Provisional limiting values for maximum vertical deflection of railway bridges for passenger comfort shall be obtained from Figures G.3 or G.4:

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