Contents ACI 530 11 Masonry WALL 002

User Manual: ACI 530-11 Masonry-WALL-002

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Software Verification
PROGRAM NAME:
REVISION NO.:

ETABS
0

EXAMPLE ACI 530-11 Masonry Wall-002
P-M INTERACTION CHECK FOR WALL
EXAMPLE DESCRIPTION
The Demand/Capacity ratio for a given axial loading and moment is tested in this
example. The wall is reinforced as shown below. The concrete core wall is
loaded with a factored axial load Pu = 1496 k and moments Mu3 = 7387 k-ft. The
design capacity ratio is checked by hand calculations and the results are
compared with ETABS program results.
GEOMETRY, PROPERTIES AND LOADING

EXAMPLE ACI 530-11 Masonry Wall-002 - 1

Software Verification
PROGRAM NAME:
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Material Properties
E=
ν=
G=

3600 k/in2
0.2
1500 k/in2

ETABS
0

Design Properties

Section Properties
tb = 8 in
h = 98 in
As1= As6 = 2-#10,2#6 (5.96 in^2)
As2, As3, As4 and As5 = 2-#6 (0.88 in^2)

f ′c = 4 k/in2
fy = 60 k/in2

TECHNICAL FEATURES OF ETABS TESTED
 Concrete wall flexural Demand/Capacity ratio
RESULTS COMPARISON
Independent results are hand calculated and compared with ETABS design
check.

Output Parameter

ETABS

Independent

Percent
Difference

Column Demand/Capacity Ratio

0.998

1.00

-0.20%

COMPUTER FILE: ACI 530-11 MASONRY WALL-002
CONCLUSION
The ETABS results show an acceptable comparison with the independent results.

EXAMPLE ACI 530-11 Masonry Wall-002 - 2

Software Verification
PROGRAM NAME:
REVISION NO.:

ETABS
0

HAND CALCULATION
Wall Strength under compression and bending
1) A value of e = 59.24 inches was determined using e = M u / Pu where M u and Pu
were taken from the ETABS test model interaction diagram. The values of M u and
Pu were large enough to produce a flexural D/C ratio very close to or equal to one.
The depth to the neutral axis, c, was determined by iteration using an excel
spreadsheet so that equations 1 and 2 below were equal.
2) From the equation of equilibrium:
Pn1 = Cc + Cs − T
where
Cc =
β1 fm′ ab =
0.8 • 2.5 •12a =
24.0a

Cs = A1′ ( fs1 − 0.8 fm′ ) + A2′ ( fs 2 − 0.8 fm′ ) + A3′ ( fs 3 − 0.8 fm′ )
T = As4 f s4 + As5 f s5 + As6 f s6

Pn1 =
24a + A1′ ( fs1 − 0.8 fm′ ) + A2′ ( fs 2 − 0.8 fm′ ) +

(Eqn. 1)

A3′ ( fs 3 − 0.8 fm′ ) − As 4 fs 4 − As 5 fs 5 − As 6 fs 6
3) Taking moments about As6:


a −tf

1 Ccf ( d − d ') + Ccw  d −
2
Pn 2 = 

e′ 
Cs 3 ( 3s ) − Ts 4 ( 2s ) − Ts 5 ( s )



 + Cs1 ( d − d ') + Cs 2 ( 4s ) + 





(Eqn. 2)

Cs1 A1′ ( f s1 − 0.8 f m′ )=
where=
; Csn An′ ( f sn − 0.8 f m′ ) ; Tsn = f sn Asn ; and the bar strains
are determined below. The plastic centroid is at the center of the section and d ′′ = 45
inch
e′ =e + d ′′ =59.24 + 45 =104.24 inch.

EXAMPLE ACI 530-11 Masonry Wall-002 - 3

Software Verification
PROGRAM NAME:
REVISION NO.:

ETABS
0

4) Iterating on a value of c until equations 1 and 2 are equal c is found to be c = 41.15
inches.
• c 0.8 • 41.15
a 0.8
=
=
= 32.92 inches

5) Assuming the extreme fiber strain equals 0.0025 and c = 41.15 inches, the steel
stresses and strains can be calculated. When the bar strain exceeds the yield strain,
then f s = f y :
 c−d '
 0.0025
 c 
c−s−d '
ε s2 = 
 0.0025
c


 c − 2s − d ' 
ε s3 = 
 0.0025
c


 d − c − 2s 
ε s4 = 
 ε s6
 d −c 
 d −c−s 
ε s5 = 
 ε s6
 d −c 
 d −c 
ε s6 = 
 0.0025
 c 

ε s1 = 

= 0.00226;=
f s ε s E ≤ Fy ; f s1 = 60.00 ksi
= 0.00116

f s 2 = 33.74 ksi

= 0.00007

f s 3 = 2.03 ksi

= 0.00102

f s 4 = 29.7 ksi

= 0.00212

f s 5 = 60.00 ksi

= 0.00321

f s 6 = 60.00 ksi

Substituting the above values of the compression block depth, a, and the rebar
stresses into equations Eqn. 1 and Eqn. 2 give
Pn1 = 1662 k
Pn2 = 1662 k
M=
P=
1662(41.15) /12 = 8208 k-ft
n
ne
6) Calculate the capacity,

φPn = 0.9 (1622 ) =
1496 kips
φM n = 0.9 ( 8208 ) =
7387 k-ft.

EXAMPLE ACI 530-11 Masonry Wall-002 - 4



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