Distribute shear to wall piers in lower portion of wall (1/2 each);
V = 3.4k/2 = 1.7 k (7.56 KN)
Shear strength of pier = (3' (12"/' (8")(174) = 49 k (218 KN) > 1.7 k (7.56 KN), OK
)
)
M = (4' (1.7)/2 = 3.4 kft (4.61 KNm)
)
M/Vl = 3.4 / (1.7)(3' = 0.67 < 3.0 (no boundary zones required in outer piers)
)
Check overall action of lower portion of wall;
Mbase = (3.4)(10' = 34 kft (46.1 KNm)
)
M/Vl = 34 / (3.4)(10) = 1.0 <3.0 (no boundary zones required in lower portion of wall)
Typical Reinforcing; (See Figure 7-6 for typical reinforcing in concrete shear walls)
Use #5 bars @ 12" on center in horizontal and vertical direction for all concrete shear walls.
f y αβλ
ld
=
Development length per ACI 318 Sec. 12.2
d b 25 f '
c
α = 1.3, β = 1.0 αβ need not be greater than 0.8, use 0.8
λ= 1.0
ld
60000(0.8)(1.0)
=
= 35
db
25 3000
For # 5 bar ld = 35*(5/8) = 22", use 24" (61 cm)
Use splice length = 1.3 ld = 1.3(24") = 31.2", use 32" (81.3cm) for all splices.
Use 2 #5 vertical bars at ends of all wall segments and at openings.
Use 2 #5 horizontal bars typical above and below openings (extend bars 24" (61 cm) past edge of
openings to develop bars) and continuously at top of walls for chord reinforcement.
(d) Horizontal bracing:
The bracing resist seismic forces only; load factor = 1.0
Design bracing for highest shear force (at shear wall line 2)
Shear to wall line 2A-2D passing through horizontal bracing = direct + torsion
V = 21.91 kips + 30%(3.2 kips) = 22.9 kips (102 KNm)
Axial (braces are at 45 degress); Axial force = 22.9 kips (1.41) = 32.3 kips (144 KN)
Try 4" Extra Strong Round Tubing (fy = 36 ksi, r = 1.48 in., A = 4.41 in.2)
The perpendicular length of the brace is approximately 8' length of brace = 8' 1.41)=11.3'
,
(
Fy
KL
(1.0)(11.3' )(12"/' )
36
=
= 1.03
π
π(1.48)
r
E
29000
2
φc Fcr = (0.85)(36ksi)(0.658) λ = 19.63ksi (135 N/mm2)
φPn = (19.63 ksi)(4.41 in.2) = 86.6 k (385 KN)
c
Check AISC Seismic Provisions; Design bracing as ordinary concerntrically braced frame (OCBF)
Slenderness: Bracing members shall have Kl/r ≤720 / Fy = 720 / 6 = 120 (Section 14.2.a)
Kl/r = (1.0)(11.3)(12)/(1.48) = 92 < 120, OK
Required Compressive Strength of brace ≤0.8 times φPn (Section 14.2.b)
c
0.8fcPn = (0.8)(86.6 k) = 69.3 k (308 KN) > 32.3 k (144 KN), OK
H3-48
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