7. Wind load
7.3 Wind load coefficient
3 When the building and structures have shapes different to those specified in Table 7.3.1 and no reference available, it should be determined by tunnel test;
4 For important building and structures with complicated shapes, they shall be determined by tunnel test.
Table 7.3.1 the Shape Coefficient of Wind Loads
Items Type Shapes and shape coefficient µs
1 Close-type grounding gable roof
The median is calculated by interpolation method
2 Close-type gable roof
The median is calculated by interpolation method
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficient µs
3 Close-type grounding arched roof
The median is calculated by interpolation method
4 Close-type arched roof
The median is calculated by interpolation method
5 Close-type shed roof
µs of the windward slope, it is adopted by Item 2.
6 Close-type high and low gable roof
µs of the windward slope, it is adopted by Item 2.
7 Close-type gable roof with scuttle
Arched roof with scuttle may be adopted by this Figure.
8 Close-type double-span gable roof
µs of the windward slope, it is adopted by Item 2.
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficientµs
9 three spans gable
roof
Windward slopeµs is adopted by Item 2
µs1 for the windward wall surface on the upper part of the midspan is adopted by the following provisions:
µs1=0.6(1-2h1/h) when h1=h, µs1=-0.6
11
Close-type gable roof with scuttle
and cover
12
Close-type gable roof with scuttle and double cover
13
Close-type unequal height
and unequal three midspans gable roof with
scuttle Windward slope µs is adopted bt Item 2 µs1=0.6(1-2h1/h)
when h1=h, µs1=-0.6
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficient µs
14
Close-type double span gable roof with
scuttle µs for the second scuttle surface of the windward is adopted by the following requirements:
When a≤4h, µs=0.2 When a>4h, µs=0.6
15 Close-type gable roof with parapet
When the parapet height is limited, the shape coefficient of the roof may be adopted as roof without parapet
16 Close-type gable roof with canopy
µs of the windward slope is adopted by Item 2.
17
Two opposite close-type gable roof
with canopy
This Fig. is applicable to that with s of 8~20mm, and µs of windward slope is adopted by Item 2.
18
Close-type pitched roof or arched roof with subsiding
scuttle
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficient µs
19
Close-type gable roof or arched roof with
subsiding scuttle
µs of the second scuttle surface of the windward is adopted by the following requirements:
When a≤4h, µs=0.2 When a>4h, µs=0.6
20 Close-type roof with scuttle wind shield
21
Close-type double span roof with scuttle
wind shield
22 Close type saw-tooth roof
µs of windward slope is adopted by Item 2.
When the tooth surface increases or reduces, it may be regulated evenly in (1), (2) and (3) three sections.
23
Close-type complicated multi-span roof
µs of the scuttle surface is adopted by the following requirements:
When a≤4h, µs=0.2 When a>4h, µs=0.6
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficient µs
24
Backing close-type gable
roof
This Fig. is applicable to conditions that shape coefficient µs in Hm/H≥2 and s/H = 0.2~0.4
Shape coefficient µs：
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficient µs
25
Backing close-type gable roof with scuttle
This Fig. is applicable to conditions that shape coefficient µs in Hm/H≥2and s/H =0.2~0.4;
26
Single-sided open type gable roof
µs of the windward slope is adopted by Item 2.
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficient µs
27
Double-side open type and four-side open type gable roof
Shape coefficient µs
The median is calculated by interpolation method
Note: 1 Roof of this Fig. is allergic to wind, so to shall consider the sign reversal condition of µs when designing;
2 Overall horizontal force to the roof caused by longitudinal wind loads;
When a≥30°, a is 0.05Aωh When a<30°, a is 0.10Aωh
A is the horizontally-projected area of the roof, while ωh is the wind pressure at roof height h;
3 When the interior stockpiled articles or the building is on the hillside, the roof suction shall be increased, and it may be adopted by Item 26 (s).
28
Semi-open gable roof of back and forth longitudinal
wall
µs of the windward slope is adopted by Item 2.
This Fig. Is applicable to building with upper part concentrically open area≥10% and≤50%.
When the open area is as high as 50%, coefficient of the leeward wall surface is instead by -1.1.
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficient µs
With gable on both Open in
The median is calculated by interpolation method Note: (b) and (c) shall consider Note 1 and Note 2 of Item 27.
3 When the interior stockpiled articles or the building is on the hillside, the roof suction shall be increased, and it may be adopted by Item 26 (a).
30 Close-type building and structures
(a) Regular polygon (including rectangular) plane
(b) Y-shape plane
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficient µs
31 Members of sections
32 Truss The shape coefficient of single truss is µst=φµs
L-shape plane II-shape plane
+-shape plane Sectional triangle plane
A=hl is the bounded area of the truss.
n is the integral shape coefficient parallel to the truss
η µ η
µ
−= − 1 1 n
st stw
µst is the shape coefficient of the single truss, and η is adopted by the following Table.
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficient µs
33 Independent wall and fence
34 Tower pier
(a) The profile coefficient µs when the angle tower pier is calculated integrally Rectangle
Wind direction ② Breakwind
coefficient φ Wind direction
① Single angle Angle (b) The shape coefficient µs when the pipe and round steel tower pier is calculated integrally When µsw0d2≤0.002, µs is adopted by the µs of angle tower pier by multiplied by 0.8;
When µsw0d2≥0.015, µs is adopted by the µs of angle tower pier by multiplied by 0.6.
The median is calculated by interpolation method
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficient µs
35 Rotating umbo
(a) The shape coefficient µs of surface distribution when it is calculated locally
36
Structures of circular section (including
chimney and tower)
Values in the table are applicable to surface smooth conditions in µsw0d2≤0.015, therein, w0 is in unit of kN/m2, and d is in unit of m.
(b) The shape coefficient µs when it is calculated integrally
Table 7.3.1 (Continued)
Items Type Shapes and shape coefficient µs
37 Rotating umbo
This Fig. is applicable to condition in µsw0d2≤0.015 (a) up and down dual-pipe
(b) back and forth dual-pipe
µs listed in the table is the same of back and forth dual-pipes, therein, the forth pipe is 0.6 (c) close packing multi-pipe
µs is the sum of all pipes
38 Dragline
The shape coefficient µsx of the horizontal component wx and the shape coefficient µsy of the vertical component wy of the wind loads:
7.3.2 If the space between multi-buildings, especially dense high-rise buildings is small, the interactive group effect of wind shall be considered. Commonly, the single building coefficient µs shall be multiplied by the mutual interference aggrandizement coefficient which can be decided according to test data of similar cases. If necessary, it can be got from the tunnel test.
2. Zone of negative pressure
—For wall face, select -1.0;
—For wall corners, select -1.8;
—For roofing partial place (fastigium with periphery and roof slope greater than 10°), select -2.2;
—For overhung members, such as cornice, canopy and sun shield, select -2.0.
Note: If the action width of wall corners and roof partial regions is 0.1 of the building width or 0.4 of the mean altitude of buildings, select the smaller one but no less than 1.5m.
II. Internal surface
For enclosed buildings, the external surface wind pressure shall be -0.2 or 0.2.
Note: The aforesaid partial wind pressure coefficient µs (1) is applicable for enclosed members with the tributary area (A) less than or equal to 1m2. If the tributary area of the enclosed member is greater than or equal to 10m2, the partial wind pressure system coefficient µs (10) shall be multiplied by the discount coefficient 0.8. If the tributary area of members is less than 10m2 but greater than 1m2, the partial wind pressure system coefficient µs (A) shall be decided according to the logarithm linear interpolation of the area.
µs(A)=µs(1)+[µs(10)-µs(1)]logA