Determination of loads on a building envelope

Example: Determination of loads on a building

envelope

This worked example explains the procedure of determination of loads on a

portal frame building. Two types of actions are considered: wind actions

and snow actions.

30,00

5,988

?

[m]

7,20

7,30

72,00

Basic data

o Total length : b = 72,00 m

o Spacing: s = 7,20 m

o Bay width : d = 30,00 m

o Height (max): h = 7,30 m

o Roof slope: ? = 5,0?

Height above ground:

h = 7,30 m

? = 5?

leads to:

h? = 7,30 - 15 tan 5? = 5,988 m

1 Wind loads

Basic values

Determination of basic wind velocity:

vb = cdir x cseason x vb,0

Where: vb basic wind velocity

cdir directional factor

cseason seasonal factor

vb,0 fundamental value of the basic wind velocity

EN 1991-1-4

? 4.2

Fundamental value of the basic wind velocity (see European windmap):

vb,0 = 26 m/s (for Aachen - Germany)

Terrain category II => z0 = 0,05 m

z > zmin

=> vb = cdir x cseason x vb,0 = 26 m/s

For simplification the directional factor cdir and the seasonal factor cseason are

in general equal to 1,0.

EN 1991-1-4

? 4.3.2

Table 4.1

Basic velocity pressure

2

b air b 2

q = 1 x ? x v

where: 1,25 air ? = kg/m? (air density)

=> 1,25 26 422,5

2

1 2

b q = x x = N/m?

EN 1991-1-4

? 4.5

eq. 4.10

Peak pressure

[ ] 2

p v m (z)

2

q (z) = 1+ 7l (z) x 1 x ? x v

Calculation of vm(z)

vm(z) mean wind velocity

vm(z) = cr(z) x co(z) x vb