Shear force tributary to each lower sloped roof area = CsW = 0.167(108.4 kips) = 18.1 kips (80.5 KN)
R element
R2A-2D = 18918 kips / in R7A-7C = 5000 kips / in Velement = V
∑R
V2A-2D = 18.1(18918) / (18918+5000) = 14.3 kips (63.6KN)
V7A-7C = 18.1(5000)/(18918+5000) = 3.78 kips (16.8 KN)
Due to symmetry, V2F-2I = V2A-2D = 14.3 kips (63.6KN)
V7G-7I= V7A-7C = 3.78 kips (16.8 KN)
The horizontal bracing is assumed to act as a rigid support to the transverse moment frames. It is further
assumed that the end shear walls (along grid lines 2 and 7) are infinitely rigid (relative to the frames).
Therefore, the horizontally braced diaphragms of the low sloped roof will transmit the shear forces from
the moment frames (shear forces tributary to the high roof) into the end shear walls.
Shear in moment frames from upper roof diaphragm = 4 (4.81 k) = 19.24 k (41.4 KN)
There are two low sloped roof areas (2A-B7 & H2-I7); assume each resists of this shear force.
Shear to each low sloped roof area = (19.24k) = 9.62 k (42.8KN)
Distribute shear to walls based on rigidity;
V2A-2D = 9.62(18918) / (18918+5000) = 7.61 kips (33.8 KN)
V7A-7C = 9.62(5000)/(18918+5000) = 2.01 kips (8.94 KN)
Due to symmetry, V2F-2I = V2A-2D = 7.61 kips (33.8 KN) V7G-7I= V7A-7C = 2.01 kips (8.94 KN)
Total Shear to walls from lower roof diaphragms;
V2A-2D = 14.3 k + 7.61 k = 21.91 k (97.5 KN) V7A-7C = 3.78 k + 2.01 k = 5.79 k (25.8 KN)
Due to symmetry, V2F-2I = V2A-2D = 21.91 kips (95.7 KN) V7G-7I = V7A-7C = 5.79 kips (25.8 KN)
Longitudinal direction: The shear walls along grid lines A and I resist all of the shear tributary to the low
sloped roofs.
Diaphragm force:
Weight tributary to each low sloped roofs (minus weight of exterior shear wall A or I):
Item
Tributary
Length /
% Solid
Area
Unit Weight
Seismic
2
Height / Width
Width
(psf / lb)
Weight
(ft. )
(ft.)
(ft.)
(kips)
LOWER ROOF
Roof A2-B7
10.0
90.0
100.0
900.0
16.9
15.2
TRANSVERSE WALLS
0.0
0.0
0.0
0.0
0.0
0.0
Wall 7A-7B
---
---
---
62.0
100.0
6.2
Wall 2A-2B
---
---
---
62.0
100.0
6.2
LONGITUDINAL WALLS
0.0
0.0
0.0
0.0
0.0
0.0
Wall B2-B7
6.5
90.0
65.0
380.3
100.0
38.0
TOTAL
65.61
292 KN
V = CsW = 0.167(65.61 kips) = 10.96 k (48.8 KN)
H3-24
Previous Page
