V. ASCE 7-16 Wind Load Generation on Building

Verify the windward loads due to wind on a portion of a building structure calculated per the ASCE 7-16 specification.

Details

The wind load is calculated for a building structure using the direction procedure for MWFRS of enclosed buildings (ASCE 7-16, Chapter 27). The following assumptions and parameters apply:

Flat roof type
Category II building (Table 1.5-1)
Basic wind speed = 108 mph
Ground height above sea level = 230 ft
Structure type of "building"
Exposure Category B
Do not consider wind speed-up over hills or escarpments
Building height = 40 ft
Building length along the wind direction, L = 30 ft
Building width normal to wind direction, B = 25 ft
Natural frequency of structure = 2 Hz (i.e., a "rigid" building per Cl. 26.2)
Damping ratio = 0.01
Enclosed building

The portion of the building below 20' in height is blocked by an adjacent structure or other obstruction. Calculate the resulting joint loads on the windward side due to wind along the X axis at the upper wall of one segment of the building.

Building structure with portion of wind load

Elevation of loaded area investigated

Validation

Directionality factor, K_d = 0.85 (Table 26.6-1)

Topographic factor, K_zt = 1.0

Ground elevation factor, K_e = e^{-0.0000362×230} = 0.9917 (Table 26.9-1)

The velocity pressure exposure coefficients (K^z) are calculated per the formulae given in Table 26.10-1:

K_{z} = | \begin{matrix} 2.01 {(15 / z_{g})}^{2 / ɑ} & for z < 15 ft \\ 2.01 {(z / z_{g})}^{2 / ɑ} & for 15 ft \leq z \leq z g \end{matrix}

(Table 26.10.1)

where

ɑ	=	7
z_g	=	1,200 ft

See the table below for the values of K^z at discrete values of z.

Velocity pressure, q_z

q_z = 0.00256×K_zK_ztK_dK_eV²

(Cl. 26.10-1)

Mean roof height = height of the building = 40 ft. Refer to table below for calculation of q_z at the mean roof height.

Gust effect factor, G

G is calculated per Cl. 26.11.4 for rigid structures:

G = 0.925 (\frac{1 + 1.7 g_{q} I_{\overline{z}} Q}{1 + 1.7 g_{v} I_{\overline{z}}})

(Cl. 26.11.4)

where

g_q = g_v	=	3.4
$\overline{z}$	=	$max \| \begin{matrix} 30 ft \\ 0.6 \times h \end{matrix} = 30 ft$
ε	=	1/3
ℓ	=	320 ft
c	=	0.3
$L \overline{z}$	=	$ℓ {(\overline{z} / 33)}^{ε} = 309.99 ft$
Q	=	$\sqrt{\frac{1}{1 + 0.63 {(\frac{B + h}{L \overline{z}})}^{0.63}}} = \sqrt{\frac{1}{1 + 0.63 {(\frac{25 + 40}{309.99})}^{0.63}}} = 0.8997$
$I \overline{z}$	=	$c {(33 / \overline{z})}^{1 / 6} = 0.3048$

Therefore, $G = 0.925 (\frac{1 + 1.7 \times 3.4 \times 0.3048 \times 0.8997}{1 + 1.7 \times 3.4 \times 0.3048}) = 0.8658$

Wall pressure coefficient, C_p = 0.8 for windward per Fig. 27.3-1.

The external design pressure, p = q_hGC_p.

The internal pressure coefficient, GC_pi = -0.18 for partially enclosed buildings per Table 26.13-1.

The internal design pressure, p_i = q_i(GC_pi) = 19.14 × -0.18 = -3.45 lb/ft²

where

q_i

the velocity pressure evaluated at the building height, h, = q_h

The design wind pressure, p, is then calculated as:

p = q_zGC_p - q_i(GC_pi)

(Eq. 29.4-1)

Table 1. Wind intensity versus height for building structure
h (ft)	K_z	q_z (lb/ft²)	p (lb/ft²)
0	0.575	14.47	13.47
15	0.575	14.47	13.47
20	0.624	15.71	14.32
25	0.665	16.74	15.04
30	0.701	17.63	15.66
35	0.732	18.43	16.21
40	0.761	19.14	16.71

Note: To compare different wind load calculations with STAAD.Pro, the tributary areas below are selected based on the applied wind area defined in the model. These do not include any surrounding wind areas outside of the indicated area, which would have wind applied in a typical situation.

Load on Nodes 21 and 22

Tributary area for nodes 21 and 22

Wind pressure at half-way between this node and level above (25') = 15.04 lb/ft².

F = (9 ft / 2) × (10 ft / 2) × 15.04 lb/ft² (10)^-3 = 0.338 kips

Load on Nodes 31 and 32

Tributary area for nodes 31 and 32

Wind pressure at half-way between this node and level below (25') = 15.04 lb/ft².

Wind pressure at half-way between this node and level above (35') = 16.21 lb/ft².

F = (9 ft / 2) × (10 ft / 2) × (15.04 lb/ft² + 16.21 lb/ft²) (10)^-3 = 0.703 kips

Load on Nodes 41 and 42

Tributary area for nodes 41 and 42

Wind pressure at roof level (40') = 16.71 lb/ft².

F = (9 ft / 2) × (10 ft / 2) × (16.71 lb/ft²) (10)^-3 = 0.376 kips

Load on Node 29

Tributary area for node 29

Wind pressure at half-way between this node and level above (25') = 15.04 lb/ft².

F = (9 ft) × (10 ft / 2) × 15.04 lb/ft² (10)^-3 = 0.677 kips

Load on Node 39

Tributary area for node 39

Wind pressure at half-way between this node and level below (25') = 15.04 lb/ft².

Wind pressure at half-way between this node and level above (35') = 16.21 lb/ft².

F = (9 ft) × (10 ft / 2) × (15.04 lb/ft² + 16.21 lb/ft²) (10)^-3 = 1.406 kips

Load on Node 49

Tributary area for node 49

Wind pressure at roof level (40') = 16.71 lb/ft².

F = (9 ft) × (10 ft / 2) × (16.71 lb/ft²) (10)^-3 = 0.752 kips

Results

Table 2. Joint loads due to wind (kips)
Result Type	Reference	STAAD.Pro	Difference
Node 21	0.338	0.33	negligible
Node 31	0.703	0.71	negligible
Node 41	0.376	0.37	negligible
Node 29	0.677	0.67	negligible
Node 39	1.406	1.42	negligible
Node 49	0.752	0.74	negligible
Node 22	0.338	0.33	negligible
Node 32	0.703	0.71	negligible
Node 42	0.376	0.37	negligible

STAAD.Pro Input

The file C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\ Verification Models\06 Loading\Wind Load\ASCE 7-16 Wind Load Generation on Building.STD is typically installed with the program.

STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 29-Jul-20
END JOB INFORMATION
INPUT WIDTH 79
UNIT INCHES KIP
JOINT COORDINATES
1 0 0 0; 2 0 0 216; 3 324 0 216; 4 216 0 0; 5 108 0 0; 6 108 0 324;
7 324 0 324; 8 324 0 108; 9 0 0 108; 10 216 0 324; 11 0 120 0; 12 0 120 216;
13 324 120 216; 14 216 120 0; 15 108 120 0; 16 108 120 324; 17 324 120 324;
18 324 120 108; 19 0 120 108; 20 216 120 324; 21 0 240 0; 22 0 240 216;
23 324 240 216; 24 216 240 0; 25 108 240 0; 26 108 240 324; 27 324 240 324;
28 324 240 108; 29 0 240 108; 30 216 240 324; 31 0 360 0; 32 0 360 216;
33 324 360 216; 34 216 360 0; 35 108 360 0; 36 108 360 324; 37 324 360 324;
38 324 360 108; 39 0 360 108; 40 216 360 324; 41 0 480 0; 42 0 480 216;
43 324 480 216; 44 216 480 0; 45 108 480 0; 46 108 480 324; 47 324 480 324;
48 324 480 108; 49 0 480 108; 50 216 480 324; 51 108 120 216; 52 216 120 216;
53 108 120 108; 54 216 120 108; 55 108 240 216; 56 216 240 216; 57 108 240 108;
58 216 240 108; 59 108 360 216; 60 216 360 216; 61 108 360 108; 62 216 360 108;
63 108 480 216; 64 216 480 216; 65 108 480 108; 66 216 480 108;
MEMBER INCIDENCES
1 11 19; 2 12 51; 3 11 15; 4 15 53; 5 16 20; 6 17 13; 7 18 54; 8 14 54; 9 1 11;
10 2 12; 11 3 13; 12 4 14; 13 5 15; 14 6 16; 15 7 17; 16 8 18; 17 9 19;
18 10 20; 19 21 29; 20 22 55; 21 21 25; 22 25 57; 23 26 30; 24 27 23; 25 28 58;
26 24 58; 27 11 21; 28 12 22; 29 13 23; 30 14 24; 31 15 25; 32 16 26; 33 17 27;
34 18 28; 35 19 29; 36 20 30; 37 31 39; 38 32 59; 39 31 35; 40 35 61; 41 36 40;
42 37 33; 43 38 62; 44 34 62; 45 21 31; 46 22 32; 47 23 33; 48 24 34; 49 25 35;
50 26 36; 51 27 37; 52 28 38; 53 29 39; 54 30 40; 55 41 49; 56 42 63; 57 41 45;
58 45 65; 59 46 50; 60 47 43; 61 48 66; 62 44 66; 63 31 41; 64 32 42; 65 33 43;
66 34 44; 67 35 45; 68 36 46; 69 37 47; 70 38 48; 71 39 49; 72 40 50; 73 19 12;
74 51 52; 75 52 13; 76 15 14; 77 53 51; 78 51 16; 79 20 17; 80 13 18; 81 54 53;
82 53 19; 83 54 52; 84 52 20; 85 29 22; 86 55 56; 87 56 23; 88 25 24; 89 57 55;
90 55 26; 91 30 27; 92 23 28; 93 58 57; 94 57 29; 95 58 56; 96 56 30; 97 39 32;
98 59 60; 99 60 33; 100 35 34; 101 61 59; 102 59 36; 103 40 37; 104 33 38;
105 62 61; 106 61 39; 107 62 60; 108 60 40; 109 49 42; 110 63 64; 111 64 43;
112 45 44; 113 65 63; 114 63 46; 115 50 47; 116 43 48; 117 66 65; 118 65 49;
119 66 64; 120 64 50;
DEFINE PMEMBER
1 73 PMEMBER 9
2 74 75 PMEMBER 10
3 76 PMEMBER 11
4 77 78 PMEMBER 12
5 79 PMEMBER 13
6 80 PMEMBER 14
7 81 82 PMEMBER 15
8 83 84 PMEMBER 16
9 PMEMBER 17
10 PMEMBER 18
11 PMEMBER 19
12 PMEMBER 20
13 PMEMBER 21
14 PMEMBER 22
15 PMEMBER 23
16 PMEMBER 24
17 PMEMBER 25
18 PMEMBER 26
19 85 PMEMBER 27
20 86 87 PMEMBER 28
21 88 PMEMBER 29
22 89 90 PMEMBER 30
23 91 PMEMBER 31
24 92 PMEMBER 32
25 93 94 PMEMBER 33
26 95 96 PMEMBER 34
27 PMEMBER 35
28 PMEMBER 36
29 PMEMBER 37
30 PMEMBER 38
31 PMEMBER 39
32 PMEMBER 40
33 PMEMBER 41
34 PMEMBER 42
35 PMEMBER 43
36 PMEMBER 44
37 97 PMEMBER 45
38 98 99 PMEMBER 46
39 100 PMEMBER 47
40 101 102 PMEMBER 48
41 103 PMEMBER 49
42 104 PMEMBER 50
43 105 106 PMEMBER 51
44 107 108 PMEMBER 52
45 PMEMBER 53
46 PMEMBER 54
47 PMEMBER 55
48 PMEMBER 56
49 PMEMBER 57
50 PMEMBER 58
51 PMEMBER 59
52 PMEMBER 60
53 PMEMBER 61
54 PMEMBER 62
55 109 PMEMBER 63
56 110 111 PMEMBER 64
57 112 PMEMBER 65
58 113 114 PMEMBER 66
59 115 PMEMBER 67
60 116 PMEMBER 68
61 117 118 PMEMBER 69
62 119 120 PMEMBER 70
63 PMEMBER 71
64 PMEMBER 72
65 PMEMBER 73
66 PMEMBER 74
67 PMEMBER 75
68 PMEMBER 76
69 PMEMBER 77
70 PMEMBER 78
71 PMEMBER 79
72 PMEMBER 80
DEFINE MATERIAL START
ISOTROPIC 3000PSI
E 3320.56
POISSON 0.2
DENSITY 8.68056e-05
ALPHA 5.55556e-06
DAMP 0.05
G 1383.57
TYPE CONCRETE
STRENGTH FCU 3
END DEFINE MATERIAL
PMEMBER PROPERTY
9 TO 16 27 TO 34 45 TO 52 63 TO 70 PRIS YD 18 ZD 12
17 TO 26 35 TO 44 53 TO 62 71 TO 80 PRIS YD 18 ZD 18
PMEMBER CONSTANTS
MATERIAL 3000PSI ALL
SUPPORTS
1 TO 10 FIXED
DEFINE WIND LOAD
TYPE 1 ASCE7:16[+X]
<! STAAD PRO GENERATED DATA DO NOT MODIFY !!!
ASCE-7-2016:PARAMS 108.000 MPH 230.000 FT 0 1 1 0 0.000 FT 0.000 FT 0.000 FT -
0 3 40.000 FT 30.000 FT 25.000 FT 2.000 0.010 0 0 0 0 0 0 0.761 1.000 1.000 -
0.850 0.992 0 0 0 0 0.866 0.800 -0.180
!> END GENERATED DATA BLOCK
INT 9.35123e-05 9.35123e-05 9.59522e-05 9.82014e-05 0.000100292 0.000102249 -
0.00010409 0.000105832 0.000107485 0.000109061 0.000110567 0.00011201 -
0.000113396 0.000114731 0.000116018 0.000116018 HEIG 0 180 203.077 226.154 -
249.231 272.308 295.385 318.461 341.539 364.615 387.692 410.769 433.846 -
456.923 480 480
EXP 1 JOINT 11 12 19 21 22 29 31 32 39 41 42 49
LOAD 1 LOADTYPE Wind  TITLE WL
WIND LOAD X 1 TYPE 1 YR 240 480 ZR 0 288
PERFORM ANALYSIS PRINT LOAD DATA
FINISH

STAAD.Pro Output

   LOADING     1  LOADTYPE WIND  TITLE WL                                     
   -----------
   JOINT LOAD - UNIT KIP  INCH
   JOINT   FORCE-X   FORCE-Y     FORCE-Z     MOM-X     MOM-Y     MOM-Z
      21      0.33      0.00        0.00      0.00      0.00      0.00
      22      0.33      0.00        0.00      0.00      0.00      0.00
      29      0.67      0.00        0.00      0.00      0.00      0.00
      31      0.71      0.00        0.00      0.00      0.00      0.00
      32      0.71      0.00        0.00      0.00      0.00      0.00
      39      1.42      0.00        0.00      0.00      0.00      0.00
      41      0.37      0.00        0.00      0.00      0.00      0.00
      42      0.37      0.00        0.00      0.00      0.00      0.00
      49      0.74      0.00        0.00      0.00      0.00      0.00