Specific construction loads for buildings

(1) Unless otherwise specified, construction loads due to working personnel, staff and visitors, with small equipment (Oca) should be modelled by uniformly distributed loads.

(2)P Where construction equipment (Qcb) may result in concentrated loads, such actions shall be taken into account.

(3)P Horizontal stability of the construction works during all its construction phases shall be secured either by detailing measures or by designing for the relevant horizontal force.

Note : Bracing is an example of detailing measure.

(4)P The horizontal load to be considered shall be assessed from wind and from effects resulting from sway imperfections and sway deformations.

(5) The horizontal stability of the structure may be checked by a simplified method consisting of applying nominal horizontal forces. Unless otherwise specified, the characteristic value of these forces should be taken equal as 1,5 % of the vertical loads resulting from the combination of actions under consideration. They should be applied at the same points as the corresponding vertical loads.

Page 24

ENV 1991-2-6:1997

4.8.3 Specific construction loads for bridges

(1) Unless otherwise specified, construction loads due to working personnel, staff and visitors, with small site equipement (0ca) on bridge decks during execution should be modelled by a uniformly distributed load. This load should be applied on the most unfavourable parts of the relevant areas and, its characteristic value should be taken equal to 1,0 kN/m2.

(2) The load due to moveable storage of construction materials (QCb) on bridge decks during execution should be modelled by a loading system including:

- a uniformly distributed load qct>;

- a concentrated load Fcb.

The uniformly distributed load and the concentrated load should be simultaneously considered in the same load case, and applied so as to obtain the most unfavourable effects.

Unless otherwise specified, their characteristic values should be taken equal to:

(3) For bridges built by the incremental launching method, horizontal forces Fh are transmitted by the deck to the supports (bearings and piers) during launching. Unless otherwise specified, the characteristic value of the horizontal force applied at the top of each pier should be taken equal to 10 % of the concomitant vertical force.

Note : In general, the friction coefficient decreases with the movement of the bridge deck; 10 % represents the "static" value of the friction coefficient, when the deck starts moving.

4.9 Seismic actions

(1) During execution, seismic actions need only be taken into account when required by the relevant competent authority or by the project specification. The stages during which verifications have to be performed should be clearly defined in the project specification.

(2) Where seismic actions need be taken into account, they should be determined in accordance with ENV 1998, taking into account the reference period of the transient situation under consideration.

(3)P The design ground accelerations ag and the importance factor yi (see ENV 1991-1) for the execution phase shall be defined in the project specification.

Was this article helpful?

0 0

Post a comment