kd = 0.308(5.81 in) = 1.79 in

Note that kd is greater than the face shell thickness, therefore the actual design section would be a T-section.

The following will show that the difference generated by assuming a rectangular section is negligible.

(450 lb/in 2)(0.308)(0.897)(24)(5.81 in)2

'

Mrm

2(12)

= 4,196 ft-lb/S . 4,147 ft-lb/S (table B-4)

Reinforcing steel resisting moment is Mrs:

FsAsjd

Mrs '

12

(24,000 lb/in 2)(0.44 in 2)(0.897)(5.81)

Mrs '

12

Note that the difference between the T-section analysis moments from table B-4 and the computed

rectangular section moments is negligible (approximately 1%).

np % (ts/d)2

kT '

np % (ts/d)

(21.5 0.0032) % 1/2(1.5/5.81)2

'

(21.5 0.0032) % (1.5/5.81)

= 0.312

6 & 6(ts/d) % 2(ts/d)2 % (ts/d)(1/2pn)

jT '

6 & 3(ts/d)

6 & [6(1.5/5.81)] % 2(1.5/5.81)2

jT '

6 & 3(1.5/5.81)

(1.5/5.81)[1/2 0.0032 21.5)

%

' 0.902

6 & 3(1.5/5.81)

AFj d

MrsT ' s s T

12

(0.44 in 2)(24,000 lb/in 2)(0.902)(5.81)

MrsT '

12

= 4611 ft-lbs . 4603 ft-lbs (table B-4)

450[1 & 1.5/(2 0.312 5.81)](24)(1.5)(0.902)(5.81)

MrsT '

12

= 4147 ft-lbs . 4147 ft-lbs (table B-4)

Note that since wind loadings are a part of the loading combination, the resisting moments of the wall cross

section may be increased by 33%. Thus, the design resisting moments for the masonry and the reinforcing

steel, respectively are:

MrmT = 1.33(4147 ft-lb/S) = 5,516 ft-lb/S

MrsT = 1.33(4611 ft-lb/S) = 6,133 ft-lb/S

Note: The masonry resisting moment controls the design:

MrmT = 5,516 ft-lb/S *> *Mmax = 4,364 ft-lb/S

....O.K.

Axial Load Check: For the 12-inch CMU wall with reinforcing spaced at 24 inches o.c., the effective area

in compression, Ae, is 68 in2/ft and the weight of the wall, W2, is 102 lb/ft2.

The axial compressive stress in the wall, fa, is determined as follows:

P % (w2)(h & x)

fa '

Ae

(1500 lb) % (102 lb/ft 2)(24 ft & 13.2 ft)

' 38.3 lb/in 2

fa '

68 in 2

The allowable axial compressive stress in wall is Fa:

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