En 1991-1-4

As a first approximation it is recommended that the wind pressure on the most rigid skin may be taken as the difference between the internal and the external pressures. If during such phases a pier may bear cantilevering deck parts or scaffoldings, a possible asymmetry of wind actions on such elements should be taken into account. Values, ytd installer taking the effect of turbulence into account may be specified in the National Annex. Search the history of over billion web pages on the Internet. Intermediate values may be found by linear interpolation.

En 1991-1-4

These need to be provided in the National Annex and Annex A, through National choice by notes in the text as indicated. The parameters n and m are defined in Expression E. Some of these equations are given in F.

For regions where it is likely that it may become very cold and stratified flow conditions may occur e. This is expressed by the Scruton number Sc, which is given in Expression E. For heights z below m the turbulent length scale may be calculated using Expression B. Jb is the outer shell diameter St is the Strouhal number as defined in E.

The zones H and I should be considered for each span of the multispan roof. If these criteria are not satisfied, specialist advice is recommended E. Where no distance x Is given in Table A. It is described by Expression F. The consideration of orographic effects beyond these boundaries is optional.

However, parties to agreements based on this European standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Books by Language uslprototype. It may also contain - decisions on the use of informative annexes, and - references to non-contradictory complementary information to assist the user to apply the Eurocode. This approach allows for the consideration of different turbulence intensities, which may differ due to meteorological conditions.

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Default values and methods are given in the main text, where the National Annex does not provide information. Ice may cause a stable cross section to become unstable.

En 1991-1-4En 1991-1-4

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Stiffness rings increase a? The end-effect factor takes into account the reduced resistance of the structure due to the wind flow around the end end-effect. The external pressure coefficients are divided into overall coefficients and local coefficients. The reference area in both cases is the gross area.

In other cases special consideration may have to be given to wind-structure interaction. It is assumed to be a safe value. It includes turbulence and roughness effects and it may be used for normal climatic conditions. Typically structures covered are chimneys or masts. However, the total reference area should not exceed that obtained from considering an equivalent plain web beam of the same overall depth, including all projecting parts.

The recomnnended procedure is to take the reference height as the height of the building. No mixing of positive and negative values is allowed on the same face. An alternative procedure is given in Annex C. For intermediate values of height z, linear interpolation may be used.

En 1991-1-4

Structural vibrations may occur if the frequency of vortex-shedding is the same as a natural frequency of the structure. See also Structural robustness. Pressure, directed towards the surface is taken as positive, and suction, directed away from the surface as negative. The objective of the programme was the elimination of technical obstacles to trade and the harmonisation of technical specifications.

Eurocode 1 Actions on structures

They may also act directly on the internal surface of open structures. This condition occurs when the wind velocity is equal to the critical wind velocity defined in E.

For circular cylinders the constants Cc and Ka. Non circular cross sections including L-, I-, U- and T-sections are prone to galloping. The terrain categories are illustrated in A. The worst combination of external and internal pressures shall be considered for every combination of possible openings and other leakage paths.

The instability is caused by the deflection of the structure modifying the aerodynamics to alter the loading. In this case specialist advice is recommended. Cc is the aerodynamic constant dependent on the cross-sectional shape, and for a circular cylinder also dependent on the Reynolds number Re as defined in E. In addition, a duopitch canopy should be able to support one pitch with the maximum or minimum load, the other pitch being unloaded.

The recommended value for the upstream distance may be obtained from A. This notation has been employed to avoid confusion with functional expressions. Such cases should be taken into account. Examples are given in Figure E.

En 1991-1-4

This includes the whole structure or parts of the structure or elennents attached to the structure, e. They are determined from the basic values of wind velocity or the velocity pressure.

The net pressure coefficient represents the maximum local pressure for all wind directions. No mixing of positive and negative values are allowed.

Both applications require special advice. The recommended method is given in Annex B.