-1601 per cent of the total weight of the service vehicle, if relevant (

(2) The horizontal force is considered as acting simultaneously with the corresponding vertical load, and in no case with the concentrated load Qfwk-

Note : This force is normally sufficient to ensure the horizontal longitudinal stability of footbridges. It does not ensure horizontal transverse stability, which should be ensured by considering other actions or by appropriate design measures.

5.5 Assessment of traffic loads on footbridges

(1) The assessment of traffic loads on footbridges is to be undertaken, for characteristic values, in accordance with 5.3.1 and 5.4, and, for the other representative values, in accordance with annex D.

Note : For the individual components of the traffic action, the other representative values are defined in annex D.

5.6 Accidental actions for footbridges 5.6.1 General

- road traffic under the bridge (ie. collision) or

- the accidental presence of a lorry on the bridge.

Note : Other collision forces (see 2.3) should be taken into account, when relevant, as specified or agreed by the relevant authority.

5.6.2 Collision forces from road vehicles under the bridge

Note 1: Footbridges (piers and decks) are generally much more sensitive to collision forces than road bridges. Designing them for the same collision load may be unrealistic. The most effective way to take collision into account generally consists of protecting the footbridges :

- by establishing safety barriers at appropriate distances before piers,

- by giving the bridges a higher clearance than for neighbouring road or railway bridges over the same road in the absence of intermediate access to the road.

The measures to be adopted should be defined or agreed by the relevant authority. Collision forces on piers

(1) Unless otherwise specified, and as for road bridges, in the absence of an appropriate risk analysis, the collision force on piers or on the supporting members of a portal bridge from road vehicles passing under the bridge is

1000 kN| in the direction of vehicle travel or 1500 kN| perpendicular to that direction, acting 1,25 m above the level of the adjacent ground surface. Additional or substitute protective measures between carriageway and piers should be specified if required. Collision forces on decks

(1) An adequate vertical clearance between the ground surface and the soffit of the deck above should be ensured in the design, when relevant. Consideration should also be given to providing protection of the deck from collision or designing for a collision force.

Note: The possibility of collision by vehicles having an illegal height should be envisaged.

5.6.3 Accidental presence of vehicles on the bridge

(1)P If no permanent obstacle prevents a vehicle from being driven onto the bridge deck, an accidental loading shall be taken into account.

(2) Unless otherwise specified, no variable action should be assumed to act simultaneously with the accidental action defined hereafter.

(3) Unless otherwise specified, the accidental loading to be used consists of a two-axle load group of 80 and 40 kN, separated by a wheel base of 3 m as shown in Figure 5.3, with a track (wheel-centre to wheel-centre) of 1,3 m and square contact areas of side 0,2m at pavement level. The braking force associated with the load group is f60l% of the vertical load.

80 kN axle le

80 kN axle le



40 kN axle load

Bridge axis direction

Figure 5.3 : Accidental loading

Note 2 : If relevant, other characteristics of the accidental loading should be defined or agreed by the relevant authority.

5.7 Dynamic models of pedestrian loads

(1) These models are those to be used, where relevant, for the design of buildings.

Note : Footbridges can be excited into vibration by users. Appropriate models should be selected for various situations (walking, running and jumping pedestrians). It has been envisaged to define models in ENV 1991-1 and ENV 1991-2. In the meantime they may be taken from national rules or from the literature.

5.8 Actions on parapets

(1 )P For footbridges, parapets shall be designed for the line load defined in 4.8.1(1).

5.9 Load model on embankments

(1) Unless otherwise specified for the particular project, the area external to a carriageway and located behind abutments, wing walls, side walls and other parts of the bridge in contact with earth, is loaded with a uniformly distributed

Was this article helpful?

0 0

Post a comment