Page 136 - Pressure Vessel Design Manual

116 Pressure Vessel Design Manual
Table 3-I* Table 3-3a”
Importance Factor (Wind Loads) Velocity Pressure Exposure Coefficients, Kz
Structure Category I Height above ground level, z Exposure Categories
I 0.87 ft (m) A B C D
II 1 .oo
Ill 1.15 0-1 5 (c-4.6) 0.32 0.57 0.85 1.03
IV 1.15 20 (6.1) 0.36 0.62 0.90 1.08
25 (7.6) 0.39 0.66 0.94 1.12
30 (9.1) 0.42 0.70 0.98 1.16
40 (12.2) 0.47 0.76 1.04 1.22
Table 3-2 50 (1 5.2) 0.52 0.81 1.09 1.27
Structure Categories 60 (1 8.0) 0.55 0.85 1.13 1.31
70 (21.3) 0.59 0.89 1.17 1.34
Buildings and structures that represent a low Category I 80 (24.4) 0.62 0.93 1.21 1.38
hazard to human life in the event of failure 90 (27.4) 0.65 0.96 1.24 1.40
All buildings not covered by the other 3 categories Category I1 100 (30.5) 0.68 0.99 1.26 1.43
Buildings and other structures containing sufficient Category 111 120 (36.6) 0.73 1.04 1.31 1.48
quantities of toxic or explosive substances to be 140 (42.7) 0.78 1.09 1.36 1.52
dangerous to the public if released.. .REFINERIES 160 (48.8) 0.82 1.13 1.39 1.55
Buildings or structures where the primary occupancy Category 111 180 (54.9) 0.86 1.17 1.43 1.58
is one in which more than 300 people 200 (61 .O) 0.90 1.20 1.46 1.61
congregate in one area 250 (76.2) 0.98 1.28 1.53 1.68
Schools, non-emergency health care facilities, Category 111 300 (91.4) 1.05 1.35 1.59 1.73
1.78
(1 06.7)
1.64
1.41
1.12
jails, non-essential power stations 350
400 (121.9) 1.18 1.47 1.69 1.82
Essential facilities Category IV
450 (1 37.2) 1.24 1.52 1.73 1.86
500 (1 52.4) 1.29 1.56 1.77 1.89
Exposure Categories Note: Linear interpolation for intermediate values of height z is acceptable.
The following ground roughness exposure categories are
considered and defined in ASCE 7-95 Section 6.5.3.1: Table 3-4
Effective Diameter, De*
0 Exposure A: Centers of large cities.
Exposure B: Urban and suburban areas, towns, city out- D Piping with Attached Piping,
skirts, wooded areas, or other terrain with numerous (Vessel Diameter or Without Ladders, and
closely spaced obstructions having the size of single + 2 x Insulation Thickness) Ladders Platforms
family dwellings or larger. - 4ft-Oin. De = 1.6D De = 2.OD
c
0 Exposure C: Open terrain with scattered obstructions 4ft- Oin. - 8ft- Oin. De = 1.4D De = 1.6D
having heights generally less than 30 ft (9.1 m). =. 8ft-Oin. De = 1.2D De = 1.4D
0 Exposure D: Flat, unobstructed coastal areas directly *Suggested only; not from ASCE.
exposed to wind blowing over open water; applicable for
structures within distance from shoreline of 15OOft or 10 Notes
times the structure height.
1. The “structure category” per Table 3-2 is equivalent to
Table 3-3* ASCE 7-95’s “building category.” Most vessels will be
Miscellaneous Coefficients Category 111.
2. The basic wind speed on the map, Figure 3-1, corre-
sponds to a 3-sec. gust speed at 33 ft above the ground,
A 113.0 0.30 0.45 180 112.0 60 in Exposure Category C with an annual probability of
B 114.0 0.45 0.30 320 113.0 30 0.02 (50-year mean recurrence interval).
C 116.5 0.65 0.20 500 115.0 15
D 119.0 0.80 0.15 650 118.0 7 3. The constant, 0.00256, reflects the mass density of air
for the standard atmosphere (59°F at sea level
~ ~ ~
‘Z,,, = minimum height used to ensure that the equivalent height f is the greater pressure, 29.92 in. of mercury). The basic equation
of 0.6 h or Z,,,,”.
‘Reprinted by permission from ASCE 7-95, “Minimum Design Loads for Buildings and Other Structures,” published by ASCE, 1995.