chapter 5.2r.pdf

7/25/2019 chapter 5.2r.pdf

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5.2 Example 2Single-storey house on a cliff top overlooking the sea

The single-storey house in Example 1 is now assumed to be located on a cliff top at a

coastal location.

Location: coast of Victoria (Region A1)

Terrain: Open sea to south. Open country for all other directions.

Topography: building is located 10m from the edge of a cliff facing south

Dimensions: as for Example 1.

Building orientation: major axis is east-west

Construction: as for Example 1.

Regional wind speed

From Table 3.1in AS/NZS1170.2, V500= 45 m/s (Region A)

Wind direction multipliers for Region A1 are given in Table 3.2. Maximum value is 1.0

(W).

z=h=4.35 m, For Terrain Category 2, Mz,cat= M4.35,cat2= 0.91 (Table 4.1(A))

Shielding

Since there are no surrounding buildings, Ms= 1.0

Topography

Profile through topography for the south, south-east and south-west directions are shown

in Figure 5.2 (a), (b) and (c) respectively.

Figure 5.2. Sections through site for three wind directions

60 m

36 m

N-S

section60 m

45 m

NE-SW

section

60 m

85 m

NW-SE

section


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Hill-shape multiplier Mhfor S winds:

H=60 m. Lu= 36 m. x = 10 m. 83.02

u

L

H

The house is within the separation zone (Figure 4.4).

L1= greater of 0.36Luor 0.4H = max{13.0 m, 24 m} = 24 m

L2= 10 24 m = 240 m

68.1240

10171.01

,

ShM (Equation 4.4(3))

Hill-shape multiplier Mhfor SW winds:

H=60 m. Lu= 45 m. x = 16 m. 67.02

u

L

H

The house is within the separation zone (Figure 4.4).

L1= greater of 0.36Luor 0.4H = max{16.2 m, 24 m} = 24 m

L2= 10 24 m = 240 m

66.1240

15171.01,

SEhM (Equation 4.4(3))

Hill-shape multiplier Mhfor SE winds:

H=60 m. Lu= 85 m. x = 15 m. 35.02

u

L

H

L1= greater of 0.36Lhor 0.4H = max{30.6 m, 24 m} = 30.6 m

L2= 10 30.6 m = 306 m

47.1

306

151

6.3035.45.3

601

,

SWhM (Equation 4.4(2))


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Site wind speed

Site wind speed for North direction, Vsit,N = 45(0.90)(0.91)(1.0)(1.0) = 36.9 m/s(Equation 2.2)

For all wind directions, site wind speeds are calculated in the following table.

Direction V500(m/s)

Md Mz,cat Ms Mt Vsit,(m/s)

N 45 0.90 0.91 1.0 1.0 36.9

NE 45 0.80 0.91 1.0 1.0 32.8

E 45 0.80 0.91 1.0 1.0 32.8

SE 45 0.80 0.91 1.0 1.47 48.2

S 45 0.85 0.91 1.0 1.68 58.5

SW 45 0.95 0.91 1.0 1.66 64.6

W 45 1.00 0.91 1.0 1.0 41.0

NW 45 0.95 0.91 1.0 1.0 38.9

Design wind speeds

Again, the building is orientated exactly N-S and E-W, and the design wind speeds, Vdes,

can be obtained by inspection from Vsit, in the above table, for the four wind directionsorthogonal to the building walls:

Vdes,N= 38.9 m/s (largest from NW to NE sector)Vdes,E= 48.2 m/s (largest from NE to SE sector)

Vdes,S= 64.6 m/s (largest from SE to SW sector)Vdes,W= 64.6 m/s (largest from SW to NW sector)

(note the much higher design wind speeds compared with those in Example 1 for this

very exposed site)

Aerodynamic shape factor

As for Example 1

Dynamic response factor

Cdyn= 1.0 (natural frequency greater than 1.0 Hertz) (Section 6.1)

Design wind pressure (major fr aming members) ultimate limi t states:

North wall

As windward wall (north wind direction):


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Cfig (external) = +0.7 (1.0) (1.0) = 0.7pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (38.9)

2(0.7)(1.0) = 636 Pa = 0.64 kPa

Cfig (internal) = -0.3 (1.0) = -0.3pint= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (38.9)

2(-0.3)(1.0) = -272 Pa = -0.27 kPa

Net pressure across wall surface = 0.64-(-0.27) = 0.91 kPa

As leeward wall (south wind direction):

Cfig (external) = -0.3 (1.0) (1.0) = -0.3pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.3)(1.0) = -751 Pa = -0.75 kPa

Cfig (internal) = 0.0 (1.0) = 0.0pint= 0 kPaNet pressure across wall surface = -0.75 kPa (acting outwards)

As side wallwest wind direction:

For first 4.35 m from west edge:Cfig (external) = -0.65 (1.0) (1.0) = -0.65

pext= (0.5 air) Vdes,2

CfigCdyn= (0.5)(1.2) (64.6)2

(-0.65)(1.0) = -1628 Pa = -1.63 kPaCfig (internal) = 0.0 (1.0) = 0.0pint= 0 kPaNet pressure across wall surface = -1.63 kPa (acting outwards)

For 4.35 m to 8.7 m from west edge:Cfig (external) = -0.5 (1.0) (1.0) = -0.5pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.5)(1.0) = -1252 Pa = -1.25 kPa

pint= 0 kPa

Net pressure across wall surface = -1.25 kPa (acting outwards)

For 8.7 m to 13.05 m from west edge:Cfig (external) = -0.3 (1.0) (1.0) = -0.3pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.3)(1.0) = -751 Pa = -0.75 kPa

pint= 0 kPa

Net pressure across wall surface = -0.75 kPa (same as leeward wall case)

As side walleast wind direction:For first 4.35 m from east edge:


2CfigCdyn= (0.5)(1.2) (48.2)

2(-0.65)(1.0) = -906 Pa = -0.91 kPa

pint= 0 kPa


For 4.35 m to 8.7 m from east edge:Cfig (external) = -0.5 (1.0) (1.0) = -0.5pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (48.2)

2(-0.5)(1.0) = -697 Pa = -0.70 kPa

pint= 0 kPa

Net pressure across wall surface = -0.70 kPa (ignore - leeward wall case governs)


5/13

For 8.7 m to (24-13.05=)10.95 m from east edge:


2CfigCdyn= (0.5)(1.2) (48.2)

2(-0.3)(1.0) = -418 Pa = -0.42 kPa

pint= 0 kPaNet pressure across wall surface = -0.42 kPa (ignore - leeward wall case governs)

East wall.

As windward wall (east wind direction):


2CfigCdyn= (0.5)(1.2) (48.2)

2(0.7)(1.0) = 976 Pa = 0.98 kPa


2CfigCdyn= (0.5)(1.2) (48.2)

2(-0.3)(1.0) = -418 Pa = -0.42 kPa


As side wallnorth wind direction:For first 4.35 m from north edge:


2CfigCdyn= (0.5)(1.2) (38.9)

2(-0.65)(1.0) = -590 Pa = -0.59 kPa

Cfig (internal) = 0.0 (1.0) = 0.0pint= 0 kPaNet pressure across wall surface = -0.59 kPa (ignore - leeward wall case governs)

For 4.35 m to (9.75-4.35=)5.4 m from north edge of west wall:


2CfigCdyn= (0.5)(1.2) (38.9)

2(-0.5)(1.0) = -454 Pa = -0.45 kPa

pint= 0 kPaNet pressure across wall surface = -0.45 kPa (ignore - leeward wall case governs)

As side wallsouth wind direction:

For first 4.35 m from south edges :


2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.65)(1.0) = -1628 Pa = -1.63 kPa

pint= 0 kPa


As leeward wallwest wind direction:


2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.3)(1.0) = -751 Pa = -0.75 kPa

pint= 0 kPaNet pressure across wall surface = -0.75 kPa (acting outwards)

West wall .

As windward wall (west wind direction):


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2CfigCdyn= (0.5)(1.2) (64.6)

2(0.7)(1.0) = 1753 Pa = 1.75 kPa


2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.3)(1.0) = -751 Pa = -0.75 kPa


As side wallnorth wind direction:

For first 4.35 m from north edge - same as east wall: -0.59 kPa.

For 4.35 m to (12.0-4.35=)7.65 m from north edge of east wall :


2CfigCdyn= (0.5)(1.2) (38.9)

2(-0.5)(1.0) = -454 Pa = -0.45 kPa

pint= 0 kPa


As side wallsouth wind direction:

For first 4.35 m from south edge - same as east wall: -1.63 kPa.

As leeward walleast wind direction:Cfig (external) = -0.3 (1.0) (1.0) = -0.3pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (48.2)

2(-0.3)(1.0) = -418 Pa = -0.42 kPa

pint= 0 kPaNet pressure across wall surface = -0.42 kPa (ignore - side wall case governs)

South wall .

As windward wall (south wind direction):Cfig (external) = +0.7 (1.0) (1.0) = 0.7pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(0.7)(1.0) = 1753 Pa = 1.75 kPa


2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.3)(1.0) = -751 Pa = -0.75 kPa


As leeward wall (north wind direction):


2CfigCdyn= (0.5)(1.2) (38.9)

2(-0.3)(1.0) = -272 Pa = -0.27 kPa

pint= 0 kPa

Net pressure across wall surface = -0.27 kPa (ignore - side wall case governs)

As side wallwest wind direction:

For first 4.35 m from west edge:


2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.65)(1.0) = -1628 Pa = -1.63 kPa



7/13

For 4.35 m to 8.7 m from west edge:


2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.5)(1.0) = -1252 Pa = -1.25 kPa

pint= 0 kPa


For 8.7 m to 13.05 m from west edge:


2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.3)(1.0) = -751 Pa = -0.75 kPa


For 13.05 m to (24-8.7=)15.3 m from west edge:


2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.2)(1.0) = -501 Pa = -0.50 kPa


As side walleast wind direction

For first 4.35 m from east edge (i.e. gable end):


2CfigCdyn= (0.5)(1.2) (48.2)

2(-0.65)(1.0) = -906 Pa = -0.91 kPa

pint= 0 kPa


For 4.35 m to 8.7 m from east edge:


2CfigCdyn= (0.5)(1.2) (48.2)

2(-0.5)(1.0) = -697 Pa = -0.70 kPa


Roof

north wind direction

north roof slope (surface 8).


2CfigCdyn= (0.5)(1.2) (38.9)

2(-0.59)(1.0) = -536 Pa = -0.54 kPa

Cfig (internal) = 0.0 (1.0) = 0.0pint= 0 kPa

Net pressure across roof surface = -0.54-(0.0) = -0.54 kPa

South roof slope (surface 9) and hip end (surface 7).


2CfigCdyn= (0.5)(1.2) (38.9)

2(-0.5)(1.0) = -454 Pa = -0.45 kPa

pint= 0 kPa


8/13


east wind direction

east roof slope (surface 10).Cfig (external) = -0.59 (1.0) (1.0) = -0.59


CfigCdyn= (0.5)(1.2) (48.2)

2

(-0.59)(1.0) = -822 Pa = -0.82 kPaCfig (internal) = 0.0 (1.0) = 0.0pint= 0 kPa


west roof slope (surface 11).


2CfigCdyn= (0.5)(1.2) (48.2)

2(-0.5)(1.0) = -697 Pa = -0.70 kPa

pint= 0 kPa


south wind direction

south roof slope (surface 9).Cfig (external) = -0.59 (1.0) (1.0) = -0.59pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.59)(1.0) = -1477 Pa = -1.48 kPa

Cfig (internal) = 0.0 (1.0) = 0.0pint= 0 kPa

Net pressure across roof surface = -1.48-(0.0) = -1.48 kPanorth roof slope (surface 8) and hip end (surface 7).


2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.5)(1.0) = -1252 Pa = -1.25 kPa

pint= 0 kPaNet pressure across roof surface = -0.27-(0.0) = -1.25 kPa

crosswind roof slopes (surfaces 10 and 11).For first 4.35 mCfig (external) = -0.9 (1.0) (1.0) = -0.9

pext= (0.5 air) Vdes,2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.9)(1.0) = -2254 Pa = -2.25 kPa

pint= 0 kPa

Net pressure across roof surface = -2.25-(0.0) = -2.25 kPaFor 4.35 m to 8.7m from windward edge

Cfig (external) = -0.5 (1.0) (1.0) = -0.5


2(-0.5)(1.0) = -1252 Pa = -1.25 kPa

pint= 0 kPa


For 8.7 m to 12 m from windward edgeCfig (external) = -0.3 (1.0) (1.0) = -0.3 (negative case)pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.3)(1.0) = -751 Pa = -0.75 kPa

pint= 0 kPa


Cfig (external) = +0.1 (1.0) (1.0) = +0.1 (positive case)pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(+0.1)(0.8) = +200 Pa = +0.20 kPa

Cfig (internal) = -0.3 (1.0) = -0.3


9/13

pint= (0.5 air) Vdes,2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.3)(0.8) = -601 Pa = -0.60 kPa

Net pressure across roof surface = +0.20-(-0.60) = +0.80 kPa

(note use of Kc equal to 0.8 in this case)

west wind direction

west roof slopes (surfaces 7 and 11).Cfig (external) = -0.59 (1.0) (1.0) = -0.59pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.59)(1.0) = -1477 Pa = -1.48 kPa

pint= 0 kPa


crosswind roof slopes (surfaces 8 and 9).For first 4.35 m

Cfig (external) = -0.9 (1.0) (1.0) = -0.9


2(-0.9)(1.0) = -2253 Pa = -2.25 kPa

pint= 0 kPaNet pressure across roof surface = -2.25-(0.0) = -2.25 kPa

For 4.35 m to 8.7m from windward edgeCfig (external) = -0.5 (1.0) (1.0) = -0.5


2(-0.5)(1.0) = -1252 Pa = -1.25 kPa

pint= 0 kPa


For 8.7 m to 13.05 m from windward edgeCfig (external) = -0.3 (1.0) (1.0) = -0.3 (negative case)pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.3)(1.0) = -751 Pa = -0.75 kPa

pint= 0 kPa


Cfig (external) = +0.1 (1.0) (1.0) = +0.1 (positive case)


CfigCdyn= (0.5)(1.2) (64.6)2

(+0.1)(0.8) = +200 Pa = +0.20 kPaCfig (internal) = -0.3 (1.0) = -0.3


2(-0.3)(0.8) = -601 Pa = -0.60 kPa

Net pressure across roof surface = +0.20-(-0.60) = +0.80 kPaFor 13.05 m to 24 m from windward edge

Cfig (external) = -0.2 (1.0) (1.0) = -0.2 (negative case)pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.2)(1.0) = -501 Pa = -0.50 kPa

pint= 0 kPa



2CfigCdyn= (0.5)(1.2) (64.6)

2(+0.2)(0.8) = +401 Pa = +0.40 kPa


2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.3)(1.0) = -751 Pa = -0.75 kPa

Net pressure across roof surface = +0.40-(-0.75) = +1.15 kPa

east roof slopes (surface 10).Cfig (external) = -0.5 (1.0) (1.0) = -0.5pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(-0.5)(1.0) = -1252 Pa = -1.25 kPa

pint= 0 kPa


10/13


Note: under-eaves pressures are same as adjacent walls.

Design loadings ul timate limit states for foundations

Use roof pressures as above multiplied by 0.8 (Ka)

Design loadings for windows (ul timate limit states)

(note: for permissible stress designdivide loads by 1.5)

For windows less than 1.44 m2

in area on north wall:


2CfigCdyn= (0.5)(1.2) (38.9)

2(+1.05)(1.0) = +953 Pa = +0.95 kPa

Cfig (internal) = -0.3 (1.0) = -0.3


2(-0.3)(1.0) = -272 Pa = -0.27 kPa

Net pressure across window = +0.95-(-0.27) = +1.22 kPa


in area on east wall:


2CfigCdyn= (0.5)(1.2) (48.2)

2(+1.05)(1.0) = +1464 Pa = +1.46 kPa

Cfig (internal) = -0.3 (1.0) = -0.3


2(-0.3)(1.0) = -418 Pa = -0.42 kPa



in area on south and west walls:Cfig (external) = +0.7 (1.0) (1.5) = +1.05 (positive case)


CfigCdyn= (0.5)(1.2) (64.6)2

(+1.05)(1.0) = +2629 Pa = +2.63 kPaCfig (internal) = -0.3 (1.0) = -0.3


2(-0.3)(1.0) = -751 Pa = -0.75 kPa



in area on east and west walls within a distance of 1.2 m

from north corners:Cfig (external) = -0.65 (1.0) (2.0) = -1.3 (negative case)pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (38.9)

2(-1.3)(1.0) = -1180 Pa = -1.18 kPa

pint = 0 kPa

Net pressure across window = -1.18-(0.0) = -1.18 kPa


in area on north and south walls within a distance of 1.2 m

from east corners:Cfig (external) = -0.65 (1.0) (2.0) = -1.3 (negative case)pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (48.2)

2(-1.3)(1.0) = -1812 Pa = -1.81 kPa

pint = 0 kPa



11/13


in area on east and west walls within a distance of 1.2 m

from south corners, and on north and south walls within a distance of 1.2 m from west

corners:Cfig (external) = -0.65 (1.0) (2.0) = -1.3 (negative case)pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(-1.3)(1.0) = -3255 Pa = -3.26 kPa

pint = 0 kPaNet pressure across window = -3.26-(0.0) = -3.26 kPa

For windows (or doors) more than 1.44 m2

in area on north wall:


2CfigCdyn= (0.5)(1.2) (38.9)

2(+0.7)(1.0) = +636 Pa = +0.64 kPa

Cfig (internal) = -0.3 (1.0) = -0.3


2(-0.3)(1.0) = -272 Pa = -0.27 kPa



in area on east wall:


2CfigCdyn= (0.5)(1.2) (48.2)

2(+0.7)(1.0) = +976 Pa = +0.98 kPa

Cfig (internal) = -0.3 (1.0) = -0.3


2(-0.3)(1.0) = -418 Pa = -0.42 kPa



in area on south and west walls:Cfig (external) = +0.7 (1.0) (1.0) = +0.7 (positive case)pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(+0.7)(1.0) = +1753 Pa = +1.75 kPa

Cfig (internal) = -0.3 (1.0) = -0.3


2(-0.3)(1.0) = -751 Pa = -0.75 kPa


For windows up to 5.76 m2

in area on east and west walls within a distance of 2.4 m from

north corners:Cfig (external) = -0.65 (1.0) (1.5) = -0.975 (negative case)pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (38.9)

2(-0.975)(1.0) = -885 Pa = -0.89 kPa

pint = 0 kPaNet pressure across window = -0.89-(0.0) = -0.89 kPa


in area on north and south walls within a distance of 2.4 m

from east corners:


2CfigCdyn= (0.5)(1.2) (48.2)

2(-0.975)(1.0) = -1359 Pa = -1.36 kPa

pint = 0 kPa



in area on east and west walls within a distance of 2.4 m from

south corners, and on north and south walls within a distance of 2.4 m from west corners:

Cfig (external) = -0.65 (1.0) (1.5) = -0.975 (negative case)


12/13


13/13

For roof cladding elements less than 5.76 m2in area, on roof surfaces 8 and 9, up to 2.4 m

from west edge of roof, and on roof surfaces 10 and 11, up to 2.4 m from south edge ofroof :

Cfig (external) = -0.9 (1.0) (1.5) = -1.35


CfigCdyn= (0.5)(1.2) (64.6)

2

(-1.35)(1.0) = -3380 Pa = -3.38 kPapint = 0 kPaNet pressure across element = -0.81-(0.0) = -3.38 kPa

For roof cladding elements less than 1.44 m2in area, on roof surface 8, up to 1.2 m from

north edge of roof :Cfig (external) = -0.59 (1.0) (2.0) = -1.18 (negative case)pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (38.9)

2(-1.18)(1.0) = -1071 Pa = -1.07 kPa

pint= 0 kPa

Net pressure across element = -1.07-(0.0) = -1.07 kPa

For roof cladding elements less than 1.44 m

2

in area, on roof surface 7, up to 1.2 m fromwest edge of roof, and on roof surface 9, up to 1.2 m from south edge of roof :Cfig (external) = -0.59 (1.0) (2.0) = -1.18 (negative case)pext= (0.5 air) Vdes,

2CfigCdyn= (0.5)(1.2) (64.6)

2(-1.18)(1.0) = -2955 Pa = -2.95 kPa

pint = 0 kPa



north edge of roof :


2CfigCdyn= (0.5)(1.2) (38.9)

2(-0.89)(1.0) = -808 Pa = -0.81 kPa

pint= 0 kPaNet pressure across element = -0.81-(0.0) = -0.81 kPa


west edge of roof, and on roof surface 9, up to 2.4 m from south edge of roof:

Cfig (external) = -0.59 (1.0) (1.5) = -0.89


2(-0.89)(1.0) = -2228 Pa = -2.23 kPa

pint = 0 kPa


Loading on battens should be applied as moving patch loads with a tributary area equal

to the batten spacing times truss rafter spacing, with the appropriate local pressure factorfor that area. For example, in this case, if the batten spacing is 0.6 m, the tributary area

would be 1.2 0.6 = 0.72 m2. Since this area is less than 0.25a

2, the local pressure

factor could be 1.0, 1.5 or 2.0, depending on the distance of the centre of the patch from

the roof edge. Over the remainder of the batten, K should be taken as 1.0; i.e. the

loading should be the same as used for major structural members.

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chapter 5.2r.pdf