A.7 Lateral load reisiting system.
Steel tank to be welded to platform and platform to be laterally supported by cross bracing in both
directions.
A.8 Select Rp, ap, and Ip factors.
ap = 2.5
(Table 10-1)
Rp = 2.5
(Table 10-1)
Ip = 1.5
(per Paragraph 10-1d)
A.10 Determine member sizes for gravity load effects.
Determine structural weights;
Weight above platform;
Weight of water;
Note: Assume tank is normally full
V = π 2 h = π(5' ) 210' = 785 - ft 3 (22.23m3)
density of water = 62.4-lb/ft3 (9800KN/m3)
R
3
Wwater = 785 - ft 3 (62.4lbs/ft )(1k / 1000 - lb) = 49.0k (218.0KN)
Weight of tank shell (1/4-in. (6.4mm) plate);
Area = π h = π(10' )10' = 314.2 - ft 2 (29.19m2)
D
w plate = 0.25" (1'/12" )490 - lb / in3 = 10.2psf (0.49KN/m2)
Wshell = 314.2 - ft 2 (10.2psf )(1k / 1000 - lb) = 3.2 k (14.2KN)
Weight of tank top and bottom (3/8-in. (9.53mm) plate);
Area = 2π 2 = 2π(5' ) 2 = 157 - ft 2 (14.59m2)
r
w plate = 0.375" (1'/12" )490 - lb / in3 = 15.3psf (0.73KN/m2)
Wtop& bot = 157 - ft 2 (15.3psf )(1k / 1000 - lb) = 2.4 k (10.7KN)
Therefore, the weight above the platform is;
Wp1 = Wwater + Wshell + Wtop& bot = 49.0k + 3.2 k + 2.4 k = 54.6k (242.9KN)
Weight of platform;
Weight of platform beams (conservatively assume beam weight at 30psf over platform plan area);
Wbeams = 30psf (10' )10' (1k / 1000 - lb) = 3.0k (13.3KN)
Weight of legs and braces (assume legs and braces at 10psf projected horizontally);
Note: Tributary height of 5-ft. (1.53m) is taken in lumping load at platform level
Wlegs& braces = 4sides(10psf )5' (10' )(1k / 1000 - lb) = 2 k (8.9KN)
Therefore, the weight to lump at the platform level is;
Wp2 = Wbeams + Wlegs& braces = 3k + 2 k = 5k (22.2KN)
Design transverse platform beams (see Figure J2-2, and J2-3);
Note: It is conservatively assumed that the middle transverse beam supports half of Wp1 with the
distribution as shown in Figure J2-3. One design will be made for this beam and used throughout for all
transverse beams.
Using load combination U = 1.4D;
Wu = 1.4(0.5(54.6k)) = 38.2k (169.9KN)
Wu L 38.2 k (10' )(12"/1' )
= 764in- k (86.3KN)
Mu =
=
6
6
Figure J2-3. Loading on middle transverse beam
Note: Beam is laterally supported throughout its span
J2-3
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