Analyse du mât en treillis d'acier haubané soumis à des charges environnementales

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Analyse du mât en treillis d'acier haubané soumis à des charges environnementales

Analyse du mât en treillis d'acier haubané soumis à des charges environnementales

mâts en treillis d'acier se classent parmi les structures porteuses de charge les plus efficaces dans le domaine de la construction de grande hauteur. L'analyse non-linéaire d'un mât en treillis d'acier haubané est effectuée en utilisant la SAP 2000 programme d'éléments finis pour différentes valeurs d'épaisseur de glace à 1500 m d'altitude. Après la définition du modèle géométrique et croix- propriétés de la section, diverses combinaisons de charge sont analysées. Finally, la vitesse du vent- relation d'épaisseur de glace est obtenue, et la vitesse maximale du vent que la structure peut supporter est déterminée pour différentes épaisseurs de glace.

  1. Introduction

Lattice mast is a general name for different kinds of steel masts.A lattice mast or truss mast is a freestanding framework mast. These structures can be used as transmission masts especially for

voltages of more than 100 kilovolts, as radio masts (self-radiating masts or carriers for aerials), or as observation masts for safety purposes. Big and heavy frame sections are not required in these

masts. This is why they are lighter than other mast types, and the modules can easily be connected to one another.

Steel lattice masts have been used for many years in the countries where the ice and wind loads are considerable. This is due to increasing demands of modern industry with regard to communication and energy. There are different styles of masts on which small wind generators are mounted: freestanding, guyed lattice, and tilt-up. Freestanding masts are relatively heavy duty, and they stay upright without the help of guy cables. Guyed lattice masts use guy cables to anchor the mast and keep it upright using a relatively small quantity of concrete. Cables stretch from three points near the top of the mast to the ground at some distance from the base of the mast. These constructions are quite light compared to freestanding masts, and therefore constitute the least expensive means for supporting a wind turbine. toutefois, they require a larger area to accommodate the guy cables.

The technical efficiency and durability of steel lattice masts have increased in recent years. The behaviour of steel lattice masts has been investigated in literature. As the design procedure is significant in these masts, the structural analysis is related to the geometrical model and section properties. Ainsi, the module production and assembly steps, and economic costs, are directly related to the design of masts. Steel lattice masts on land are vulnerable structures. They are mostly affected by environmental loading. Wind loads are the most effective design criteria for these structures. toutefois, the ice effect must also be taken into consideration, especially at high elevations. In cold regions, these two effects are combined. Donc, the relationship between the wind and ice must be investigated by conducting proper finite-element analyses to avoid the collapse of such structures. In this paper, the non linear analysis of a guyed steel lattice mast 80 m in height is performed using the SAP 2000 program. While the model is constituted according to TS 648 load conditions are taken from TS 498. The altitude of the structure is taken to be 1500 m, and the snow region IV is adopted, which is the most conservative option. De cette façon, the analysis can also be used for other snow regions. The structure was first analysed without any ice effect. Afterwards, the ice thickness was gradually increased, and the relationship between the wind speed and ice thickness was determined.

  1. Materialand method

Proper sections and angles of the steel lattice mast are first determined. Afterwards, the three dimensional finite element model is given in Figure 1. Top view of the model is presented

in Figure 2. Face sections of the model, showing the distances with angles, are shown in Figure 3 and Figure 4.

Figure 1. 3-ré modèle

 

Figure 2. Haut vue

 

 

Figure 3. UNE et B visage sections

 

 

Figure 4. C visage section

Table 1. Matériel properties

Matériel

type

Résistance à la traction

Force

[MPa]

rendement

Force

[MPa]

ST52 (S355)

510

360

Table 2. section properties

Membre

type

Section

type

Taille

[mm]

Colonne

membres

Tuyau

48×7

Verticale

membres

Circulaire

16

Diagonale

membres

Circulaire

16

Guy members

Circulaire

16

Table 3 La vitesse du vent et les charges selon la hauteur

Hauteur

[m]

Vent la vitesse

“v”

[Mme]

Vent charge

“q”

2

[kg/m ]

0-8

28

50

8-20

36

80

20-80

46

130

A module 3015 mm in length is made of steel members. Columns are placed at an angle of 900 to the ground. Vertical steel members connect columns to one another, and are placed vertically with respect to the columns. Diagonal members are placed by definite angles to the columns, and they also connect the columns to one another. A column with diagonal and vertical members that constitute the module, are shown in Figure 5.

 

Figure 5. Module membres

Guy members and modules are named according to the total height from the ground level. The guy and section numbers, with related heights, are presented in Figure 6.

Table 4. Height et neige

Altitude

[m]

Neige

Région

Neige charge qs

2

[kg/m ]

1500

IV

176

Table 5. La glace properties

Poids de unité volume

[kN / mm³ ]

7

il y a 26 modules dans le mât en treillis. La colonne, verticale,et des éléments diagonaux dans chaque face du module sont shownin Figure 7. la direction des vents positifs et négatifs qui affectent la
module sont également présentés dans la figure.

Table 6 propriétés de la section

 

Membre

 

Section

type

Section

taille

[mm]

Section

circonférence

[cm]

Section

surface

2

[cm ]

Colonne

Tuyau

48×7

15.08

9.02

Verticale

Circulaire

16

5.03

2.01

Diagonale

Circulaire

16

5.03

2.01

Gars

Circulaire

16

5.03

2.01

Colonne

Tuyau

48×7

15.08

9.02

Verticale

Circulaire

16

5.03

2.01

Diagonale

Circulaire

16

5.03

2.01

Gars

Circulaire

16

5.03

2.01

Colonne

Tuyau

48×7

15.08

9.02

Verticale

Circulaire

16

5.03

2.01

Diagonale

Circulaire

16

5.03

2.01

Gars

Circulaire

16

5.03

2.01

Colonne

Tuyau

48×7

15.08

9.02

Verticale

Circulaire

16

5.03

2.01

Diagonale

Circulaire

16

5.03

2.01

Gars

Circulaire

16

5.03

2.01

 

 

Load combinations used in the analysis are given in Eqn (1) and Eqn (2) comme suit. The combinations are constituted by Snow loads, ice loads according to ice thickness values,

and wind loads effecting different heights of the lattice mast with wind speeds are given in Table 7.

 

Membre

Neige

charge

2

[kg/m ]

Distribué

neige charge

[kg/m]

La glace

Épaisseur

[mm]

Distribué

ice charge

[kg/m]

Vent

la vitesse

[km / h]

Vent charge selon à la taille

[kg/m]

0-8 m

8-20 m

20-80 m

Colonne

 

176

 

30

5.15

 

209

12.18

19.49

26.81

Verticale

membre

4.42

3.03

4.06

6.50

8.94

Diagonale

membre

4.42

3.03

4.06

6.50

8.94

Gars

4.42

3.03

4.06

6.50

8.94

Colonne

 

176

 

20

2.99

 

217

12.63

20.21

27.79

Verticale

membre

4.42

1.58

4.21

6.74

9.26

Diagonale

membre

4.42

1.58

4.21

6.74

9.26

Gars

4.42

1.58

4.21

6.74

9.26

Colonne

 

176

 

10

1.28

 

223

12.96

20.73

28.50

Verticale

membre

4.42

0.57

4.32

6.91

9.50

Diagonale

membre

4.42

0.57

4.32

6.91

9.50

Gars

4.42

0.57

4.32

6.91

9.50

Colonne

 

176

 

0

 

226

13.14

21.03

28.92

Verticale

membre

4.42

4.38

7.01

9.64

Diagonale

membre

4.42

4.38

7.01

9.64

Gars

4.42

4.38

7.01

9.64

effets de charge éléments latéraux. charge de neige distribué est calculée en considérant haut surface des éléments.

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