ML19309G034

Response to Comments on App B of Coleville Rept of 800213 on Trojan Masonry Walls

ML19309G034
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Site:	Trojan File:Portland General Electric icon.png
Issue date:	04/08/1980
From:	Colville J AFFILIATION NOT ASSIGNED
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TAC-12369, NUDOCS 8005020241
Download: ML19309G034 (9)

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i Response to Comments on " Appendix B of Dr. Colville's Report of 1/13/80 on Trojan Masonry Walls".

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Dr. James Colville, P. E.

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April 8, 1980.

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Response to Comments on " Appendix B of Dr. Colville's Report of 2/13/80 on Trojan Masonry Walls ".

f.

' 1 The following is presented in response to comments submitted by i

A. Schwenler, March 15, 1980, Attachment 3.

Attention will be focused on the computation of the effective post cracking flexural rigidity of the double wythe walls assuming composite action, since this parameter is of primary importance in evaluating the wall capacity with respect sto weak axis bending.

Consideration of only the grout cell fill in checking the behavior of the mortared double wythe walls is considered reasonable since previous calculations (1) indicate that tensile cracking of the mortar bed joints will occur under inertia loading. Section properties of the cell fill for stiffness computations can be computed using average properties of the b1c:k cavity (2). Using data from page '16 of Ref.(3), the following section preperties may be computed for the 16" thick wall:

Area of cells = (91.5 - 50.1) = 41.4 in /ft Moment of inertia of cells with respect to the block 4

(443.32 - 363.83) = 79.49 in /ft cens.oid

=

Assuming composite action I = 79.49 (2) + 2(41.4 )(4) 4

= 1483.8 in /ft The cell dimensions may be computed as follows:

2 41.4 in /ft bd

=

bd3= 79.49 in /ft 4

12 giving b = S.625 ins and d = 4.8"

(

_-p,,-.g,g-w

,w, g7 3 g,

2.

Tnus the se:tien modulus of the corposite section is 3dE3 3 1483 8 3

231.8 in /ft s.

=

j (4 + d/2) 6.4 i

3 19.32 in h

=

e (Nete that this value of 5 is roughly 141, lower than the value corputed on page EA - 2 of Attachment 3.)

Using a moc'ulus of rupture of 7.5 h the cracking moment, Mer' IS 7.5 /5000 19.32 10.24 ft. k/ft.

M

=

cr 1000 Using #6 at 16" in each wythe of the wall (as specified by Bechtel in ), the neutral axis of the cracked section may be computed as follows:

2 2

0.33 in fft, A

= 0. 44 in xH

=

s-16 A ra.ior question arises concerning the appropriate modulus of elasticity

~

6 of the grout cell fill.

Bechtel has used a value of 4.3(10 ) psi which apyears to be d'erived from ACI - 31; - 77, assuming w = 150 pcf and fe'* 5000 psi.

However, little information is available on the relationship between E and fe' for high slump grout (4,6). From page c

26 of Ref. (5), the modulus of elasticity of 5000 psi grout is estimated 6

to be around 2.8 (10 ) psi. Although an attempt will be made to further verify this value, in the abs [ence of other data, this value will be used in the following computations.

Thus n = 10.4 and

8. 625 (c ) 2

10. 4 (0. 33) (8+ 2. 4 - c)

=

giving c =

1.84 in 10.4(.33)(10.4 - 1.84)2 6.625(1.84)3

'cr

+

=

3

4 269.4.in /ft 17.91 + 251.5

=

=

4 22.45 in /in

=

0 The thermal moment based on'a 50 F gradient is "th.

E0-(6)(10-6)(2.8)(10 )

6 19.32 8.1 ft.k/ft.

=

2 1000 (this value has been computed using Bechtel data, but with S = Section modulus of the uncracked section).

The moment due to interstory drift given by Bechtel of 2.8 ft k/ft seems to be based on a wall thickness of only 8".

Using t = 15.625" and M=

max moment, the interstory drift moment = 6.0 ft k/ft.

This value will be used below.

4 Assuming pinned ends, and I =

1483.8 in /ft, the frequency becomes 6

f

=

7.12 2.8(10 )(1483.8)(1728)(386.4) 2(16x12) 2 /5

\\/

( 5.625)(138) 14.1 cps.

=

Since reference (2) of Bechtel Attachment 3 is not presently available the frequency considering partial support of the columns will be estimated by interpolation of columns 5 and 6 of Table 1, Bechtel Attachment 3.

Thus the contribution of the columns will be considered, although the reliability of this support may be questionable.

By interpolation, use f = 17.2 cps. giving a = 0.6 (for El. 61'.)

The bending load

.6(138)(15.625) 107.8 psf.

=~

=

12 W12 M

3.45 ft. k/ft.

=

=

8 The total moment 8.1 + 6. 0 + 3. 4 5 17.55 ft.k/ft.

=

=

1

-._ _ _ _._-_:=-

According to AC1-318-77, 6

3

}

{ Mer si E

-I cr M

I

=

e Na

\\"/

/

! 10.24

+

1-10.24 269.4 (1483.8)

=

(17.55 (17.55 4

510.6 in /ft.

294.7 + 125.9

=.

=

4 42.5 in /in

=

Recomputing f gives 11.9 cps.)

8.3 cps.

(By interpolation, use f f

=

=

6.04 ft k/ft.

1.05, and M

Thus a

=

=

Allowing a reduction in the thermal moment due to the reduced scaent of inertia gives f

)

"th 8.1 2.79 ft k/ft.

=

=

y 14.83 ft k/ft.

The total moment

=

2. 79 + 6. 0 + 6. 04

=

giving 4

4 55.7 in /in 669 in /ft.

488 + 180.7 I,

=

=

=

Repeated iterations following the above procedure converge to the following 13.3,

I

= 702 in#/ft.

f

=

e 0.77 a =

4.46 ft k/ft.

inertia M

=

138.0 psf.

inercia w =

i l

I

The shearing force at the wall ends 4 (12)(15.625)

=

+

1104 750 1854

=

+

=

The collar joint shear stress 1854 (41.4)(4)

=

1483.8 (12) psi

=

17.2 psi

=

~

at E1. 77 Using the uncracked section, f = 17.2 cps, giving a =

.77 4.43 ft k/ft thus M

=

8.1

+ 6.0 + 4.43 18.53 ft k/ft.

M

=

=

total 4

474.3 in /ft.

1, 250.4

+

223.9

=

=

Recocputing gives f

8.05 ft k/ft.

11.5 cps.,

a

=

1.40, M

=

=

16.64 ft k/ft.

8.1(474)

M

+

6.0 + 8.05

=

=

g 33 1483.8 4

345.7 + 206.6 552 in /ft.

I

=

=

e Recomputing 1.33, M=

7.65 ft k/ft f

12.3 cr,s, a =

=

' etal

(

16.66 ft k/ft, t

=

+

6.0 + 7.65

=

83 8 o.k.

t 9

1 e,% w --

,-wem-+*

e A

.---w

=*m.

6.

239 psf thus a =

1.33, w =

a 2662 lbs.

V 23S(16)

+

750

=

=

2 24.8 psi 2662 (41.4)(4) collar joint shear stress

=

=

1483.8(12) at E1. 93

~

0.80 Using f

17.2 cps, a =

=

18.7 ft k/ft.

8.I'+ 6.0 + 4.L thus M

=

a1 4cf,in#/ft I

243.6 + 225.2

=

=

e 7.76 ft k/ft.

Recomputing gives f 1.35, M

11.4 cps, a =

=

=

16.32 ft k/ft.

8.1 (468. Ei

+

6.0 + 7.76 M

=

=

total 1483.8 4

568.4 in /ft, 365.5 +

202.9 I

=

=

e Recomputing 7.53 ft k/ft.

f 1.3, M

12.4 cps, a

=

=

=

16.63 ft k/ft.

8.1(568.4)

+

6.0 + 7.53 M

=

=

total 3433,3 4

552.9 in /ft.

I 346.4 + 206.5

=

=

e 7.59 ft k/ft.

Recomputing f = 12.2 cps, a =

1.32, M

=

16.60 ft k/ft.

8.1(552.9)

+

6.0 + 7.59 M

=

=

total 1483.8 o.k.

237. 7 ps f.

thus, a = 1.32, w =

V 2647 psi

=

collar joint,saear stress 24.6 psi

=

l l

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l

~

7.

In summary, these calculations show:

(a)

Collar joint shear bond stresses as follows:

17.2 psi El. 61 stress

=

24.8 psi El. 77 stress

=

24.6 psi E1. 93 stress

=

These values are cosiderably in excess of the value of 12 psi which is considered equal to the collar joint shear bond capacity

~

(b)

Flexural rigidity values as follows:

6 6

1.97(10 ) k in 2.8(10 ) 702 El. 61 EI

=

=

0 6

1.55(10 ) k in El. 77 EI 2.8(10 ) 552

=

=

6 6

'2.8(10 ) 552.9 =

1.55(10 )

k in El. 93 EI

=

These values are much smaller than b (Ig+I r)Ec 6

6 h (3815 + 347)(2)(10 )

4.16(10 )

k in

=

=

1000 suggested by Bechtel.

The post cracking effective nament of inertia is around 37% to 47% of the gross uncracked moment of inertia.

As a result of these computation.:, the magnitude of collar joint shear stress of 9.2 psi, given on page 4 of Bechtel Attachment 3, is too low.

Considering thermal effects, interstory drift and inertia loading, the stresses range between 17 psi and 25 psi.

Note that these values will j

increase significantly if the steel columns do not in fact provide elastic restraint to the wall edges. On the other hand, these stresses may be overestimated if it can be shown that the modulus of elasticity of the grout co7 crete exceeds 2.8(10) psi.

p 4

~

REFERENCES i

(1)

Colville, J.,

" Report on Design Criteria for Masonry Walls in the Trojan Power Plant ", Submitted to NRC, Division of Operating Reactors, March, 1980.

(2)

Building Code Requirements for Concrete Masonry Structures (ACI 531-79) and Commentary - AC1531R-79, American Concrete Institute, Detroit, Michigen, 1979.

~

(3) Reinforced Concrete Masonry Design Tables, National Concrete Masonry Association, 1971.

(4)

Private Communication, A.L. Isberner, Portland Cement Association, Skokie, Ill., April 4, 1980.

(5) Hegemier, G. A.,

" Mechanics of Reinforced Concrete Masonry:

A Literature Survey ",

Report No. AMES - NSF TR-75-5, NSF Report, Sept. 1975.

(6) Private Communication, J. Amrhein, Masonry Institute of America Los Angeles, CA.,

April 8, 1980.

0

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