precast concrete column and footing...

Precast concrete column and footing connections-epoxy

Authors Al-Naimi, Sarmad Fakhri, 1943-

Publisher The University of Arizona.

Rights Copyright © is held by the author. Digital access to this materialis made possible by the University Libraries, University of Arizona.Further transmission, reproduction or presentation (such aspublic display or performance) of protected items is prohibitedexcept with permission of the author.

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Link to Item http://hdl.handle.net/10150/318727

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PRECAST CONCRETE COLUMN AND FOOTING

CONNECTIONS-EPOXY

by -

Sarmad F ak h r i Al-Naimi

A T h es is S ubm itted to th e F a c u l ty o f th e

DEPARTMENT OF CIVIL ENGINEERING

In P a r t i a l F u l f i l lm e n t o f th e Requirem ents For th e Degree o f

MASTER OF SCIENCE

In th e G raduate C o llege

THE UNIVERSITY OF ARIZONA

1 9 6 8

STATMENT BY AUTHOR

T his t h e s i s has been s u b m it te d in p a r t i a l f u l f i l l m e n t o f r e q u irem en ts f o r an advanced deg ree a t The U n iv e r s i t y o f A rizona and i s d e p o s i te d in th e U n iv e r s i ty L ib ra ry t o be made a v a i l a b l e to bo rrow ers under r u l e s o f th e L ib ra ry .

B r i e f q u o ta t io n s from t h i s t h e s i s a re a l lo w a b le w ith o u t s p e c i a l p e rm is s io n , p ro v id ed t h a t a c c u ra te acknowledgment o f so u rc e i s made. R equests f o r p e rm is s io n f o r ex tended q u o ta t io n from o r r e p ro d u c t io n o f t h i s m a n u sc r ip t in whole o r in p a r t may be g ra n te d by th e head o f th e m ajor departm en t o r th e Dean o f th e G raduate C o lleg e when in h i s ju d g ment th e p roposed use o f th e m a te r i a l i s in th e i n t e r e s t s o f s c h o l a r s h ip . In a l l o th e r i n s t a n c e s , however, p e rm is s io n must be o b ta in e d from th e a u th o r .

SIGNED: S . ^ f - V x

APPROVAL BY THESIS DIRECTOR

T his t h e s i s has been approved on th e d a te shown below:

/ 1 . I _________QSL V, I P } I 9 C37 James D. K riegh y y DateAssoc. P ro f . o f C iv i l E n g in ee r in g

ACKNOWLEDGMENTS

The a u th o r w ishes t o ex p ress h i s deep g r a t i t u d e to h i s t h e s i s

d i r e c t o r . P r o f e s s o r James D. Kriegh f o r h i s a c t i v e i n t e r e s t , h e l p f u l

gu idance and c o n s t r u c t i v e s u g g e s t io n s .

The a s s i s t a n c e g iven by Mr. Brooks M uterspaugh and Mr. Louis

Gemson in h e lp in g p r e p a re th e specim ens i s a p p r e c ia t e d .

This r e s e a r c h was funded by th e E n g in ee r in g Experim ent S t a t i o n

o f th e U n iv e r s i ty o f A rizona .

TABLE OF CONTENTS

Page

LIST OF ILLUSTRATIONS........................................... v

LIST OF TABLES..................................................................................................... v i i

ABSTRACT................................................................. v i i i

CHAPTER 1 ........................................................................................................................................... 1

. I n t r o d u c t i o n ................................................................... 1

CHAPTER I I ................................................................................................. 10

D es ig n ............................................................................ 10A. The Column....................................................................................................... 10B. The F o o t in g .................................................................................................... 19

CHAPTER I I I ................................................................................................................................ 25

N atu re and Scope o f T e s t s ...................................................................................... 25In s t r u m e n ta t i o n and T e s t Equipm ent.......................................................... 25C olum n-foo ting C o n n e c t io n ............................................................................. 29

CHAPTER IV................................................... 31

T es t R e s u l t s ..................................................................................................................... 31M om ent-Rotation C h a r a c t e r i s t i c s ............................................. 32

CHAPTER V............................................................................ 42

A n a ly s is o f T e s t R e s u l t s and Recommendations................................................ 42Recommendations f o r F u r th e r R e se a rc h ..................................................... 50

APPENDIX....................................................................................................................................... 51

M a te r i a l s and F a b r i c a t i o n ...................................................................................... 51

REFERENCES................................................................................................................................... 56

iv

LIST OF ILLUSTRATIONS

Figure Page

1. Column P laced i n t o a C a ly x ............ 3

2. Welded J o i n t o f Column to F o o t in g ................... 5

3. J o in in g o f Column to F o o t i n g . . . . . . ................. 6

4. J o in in g o f Column t o F oo ting by P ro t ru d in g Loop-formedS te e l B a r s .............................. 7

5. J o in in g o f Column to F oo ting B o l t s ..................... 8

6. S t r a i n o f th e E c c e n t r i c Loaded Column .............. 11

7. F orces A cting on E c c e n t r i c Loaded Column........................................... 12

8. S t r e s s - s t r a i n o f th e M o n o l i th ic Column................................................ 13

9. M o n o li th ic Colum n...................... 17

10. Epoxy Column ................... 18

11. M o n o li th ic F o o t i n g . ............................ 20

12. M o n o li th ic F oo ting D e t a i l s .......................... 23

13. Epoxy F o o tin g . .................................................................. 24

14. T e s t A rrangem en t............................... 26

15. T es t S e t -u p I n s t r u m e n t a t i o n . ........... ' 27

16. Gauges f o r M easuring D e f l e c t i o n s . . . . . . . . . ................... 28

17. Load E c c e n t r i c i t y ................................. 31

18. Column R o t a t i o n . ............................... 33

19. M-0 B ehavior o f th e M o n o li th ic U n i t ...................... 35

20. M-0 B ehav io r o f th e 5 Inch Depth U n i t . . . . . .......................... 36

21. M-0 B ehav ior o f t h e 10 Inch Depth U n i t . . . . . . . . . . . . . . . . . . . . . 37

v

vi

LIST OF ILLUSTRATIONS--C ontinued

Figure Page

22. M-0 B ehav io r o f t h e 15 Inch Depth U n i t , ................... ............................ 38

23. Comparison o f t h e M o n o l i th ic , PCA M o n o l i th ic , 5 , 10 and 15Inch U n its M-0 B e h a v io r ........................................................................... 39

24. Modes o f F a i l u r e ................................... 40

25. 5 Inch Depth Recess F a i l u r e ........................ 41

26. 10 Inch Depth Recess F a i l u r e .......................................................................... 41

27. E f f e c t o f Moment Arm on th e R e s u l t a n t F o r c e s .................................... 43

28. E le v a t io n o f t h e Gauges - 0 B ehav io r o f t h e M o n o l i th ic U n it . 45

29. E le v a t io n o f t h e Gauges - 0 B ehav io r o f th e 5 Inch DepthU n i t .............................. 46

30. E le v a t io n o f t h e Gauges - (3 B ehavior o f th e 10 Inch DepthU n i t ................................................... 47

31. E le v a t io n o f t h e Gauges - 0 B ehav io r o f t h e 15 Inch DepthU n i t ....................... 48

32. Comparison o f th e M o n o l i th ic , 15 Inch Depth and th eT h e o r e t i c a l M-0 B e h a v io r ......................................................................... 49

A. P r e c a s t Column and F oo ting S t e e l ................................................................ 52

Al. P r e c a s t U n i t s - -M o n o l i th ic S t e e l ................................................................... 55

LIST OF TABLES

Table Page

1. S t i f f n e s s V a lu e s ............................................... 34

2. Moment P e r c e n t a g e ...................................................................... 42

A I . Column and F o o tin g C oncre te S t r e n g t h . .......................... 51

-A ll . Epoxy S t r e n g t h ........................ 53

v i i

ABSTRACT

T his e x p e r im e n ta l s tu d y concerns epoxy g ro u te d c o n n e c t io n s i n

. p r e c a s t c o n c re te s t r u c t u r e s . The method o f t r e a tm e n t fo l lo w s th e con

c e p t o f "C onnec tions i n P r e c a s t C oncre te S tru c tu re -C o lu m n Base P l a t e s " ,

which has been done by R„ W. LaFraugh and D. D. Magura o f th e P o r t la n d

Cement A s s o c ia t io n . However, i n s t e a d o f u s in g a s t e e l b a s e p l a t e , epoxy

was used t o s e c u re th e column in a r e c e s s in th e f o o t i n g .

The dep th o f column i n s e r t i o n o f th e f o o t in g was v a r i e d and th e

r o t a t i o n a l e f f e c t s under e c c e n t r i c lo a d in g was compared to a m o n o l i th ic

c o lu m n -fo o tin g .

I t was found t h a t th e r e s i s t i n g f o r c e in th e fo o t in g v a r i e s w ith

t h e dep th o f th e r e c e s s , a 15 inch dep th behav ing s u b s t a n t i a l l y as th e

m o n o l i th ic u n i t i n t h i s s tu d y .

CHAPTER I

INTRODUCTION

The concep t o f p r e c a s t c o n c re te i s as o ld as t h e p ro d u c t io n o f

cem ent, which was used in th e form o f m ortar , by th e Romans and E g y p t ian s .

I t was n o t u n t i l th e development o f P o r t la n d cement d u r in g th e n in e t e e n t h

c e n tu ry t h a t th e f i r s t commercial p r e c a s t c o n c re te members were a v a i l a b l e ,

and i t has been o n ly in th e l a s t tw en ty y e a r s t h a t th e p r e c a s t i n g o f

m a jo r s t r u c t u r a l members f o r b u i l d in g s and b r id g e s has become a commonly

a c c e p te d p r a c t i c e . In c e r t a i n l o c a l i z e d a r e a s o f Europe, p r e c a s t i n g had

been in t ro d u c e d as an e x p e d ie n t in c o n n e c t io n w ith th e r e c o n s t r u c t i o n o f

war-damaged b u i l d i n g s . In th e p o s t World War I I p e r io d , s t e e l and wood

were i n v e ry s h o r t su p p ly . C oncre te was used as a s u b s t i t u t e , and by

p r e c a s t i n g i t , t h e wood n e c e s s a ry f o r th e forms cou ld be used s e v e r a l

t im e s . By th e t im e th e s h o r ta g e no lo n g e r e x i s t e d , th e method o f p r e

f a b r i c a t i o n had l a r g e l y r e p la c e d th e method o f c a s t - i n - p l a c e c o n c r e te .

For th e above r e a s o n s , Europe i s much f a r t h e r advanced th a n th e U n ited

S t a t e s i n th e a r t o f p r e f a b r i c a t i o n .

The c p s t o f m o n o l i th ic r e i n f o r c e d - c o n c r e t e s t r u c t u r e s i s d i s

t r i b u t e d in t o t h r e e n e a r l y equal p a r t s : c o n c r e t in g , r e in fo rc e m e n t , and

s c a f f o l d i n g . For s t r u c t u r e s o f g r e a t h e ig h t th e c o s t o f form ing and

s c a f f o ld i n g m ight re a c h s i x t y p e r c e n t o f th e t o t a l c o s t . T h e re fo re ,

s o lu t i o n s sh o u ld be sough t to d im in ish th e c o n s id e r a b le c o s t s o f form

work. The p r e f a b r i c a t i o n o f r e i n f o r c e d - c o n c r e t e s t r u c t u r e s i s a

s o l u t i o n a p p r o p r i a t e f o r th e above m entioned problem . By p r e f a b r i c a t i o n

th e w as te o f t im b e r f o r s c a f f o l d s can be e l im in a te d a lm ost e n t i r e l y ,

w h ile t h e amount needed f o r s h u t t e r i n g ( i . e . form ing) can be d im in ish ed

t o about one t h i r d o f th e q u a n t i t y n e c e s s a ry f o r a s i m i l a r m o n o l i th ic 2

s t r u c t u r e .

A c o lu m n -fo o t in g c o n n e c t io n i s a main f u n c t io n in a lm ost ev e ry

k in d o f s t r u c t u r e , b ecau se i t t r a n s f e r s th e load o f t h e s t r u c t u r e to th e

f o o t i n g s . Many d i f f e r e n t approaches have been made f o r t h i s ty p e o f

end c o n n e c t io n .

Three v a r i a t i o n s o f one method a r e shown i n F ig u re 1. The f i r s t

(A) can be u sed f o r sm a ll f o o t i n g s , t h e m idd le (B) f o r a v e ra g e s i z e

f o o t i n g s , and t h e t h i r d (C) f o r l a r g e f o o t i n g s . In (A) t h e dep th o f th e

ca ly x i s d im ensioned ac c o rd in g t o S o v ie t p r a c t i c e and i s 1 .1 t im es th e

le n g th o f th e lo n g e r s id e o f th e column. In Hungary, i n s t e a d o f th e

f a c t o r 1 .1 , th e f a c t o r 1.5 i s u s u a l l y a p p l i e d (shown i n B § C ) . A ccord

ing t o a r u l e sometimes used i n Europe, th e dep th o f th e ca ly x shou ld be

equa l t o 12-15% o f t h e le n g th o f th e column. The opening o f th e c a ly x

i s 5-10 cm. g r e a t e r in a l l d i r e c t i o n s th a n th e c r o s s - s e c t i o n o f th e

column. T h is i s t o e n ab le th e v i b r a t o r t o be o p e ra te d w h ile c o n c r e t in g .

To en su re t h e p ro p e r v e r t i c a l p o s i t i o n o f th e column, a s t e e l p l a t e i s

p la c e d a t t h e bottom o f t h e c a ly x and checked by l e v e l in g b e f o r e con

c r e t i n g . A s i m i l a r s t e e l p l a t e i s a l s o p u t on th e low er end o f th e

column. When p o s i t i o n i n g th e column, th e s e two s t e e l p l a t e s must b e s e t ,

2on each o t h e r .

A second method u t i l i z e s a r i g i d w elded j o i n t . In t h i s c a se t h e

column i s t e m p o r a r i l y su p p o r te d by a t o n g u e - l i k e e x te n s io n r e s t i n g on th e

h H h H

.5b

5 - 1 0

(A) (B) (C)

F igu re 1. Column p la c e d in t o a c a ly x .

(1 - c o n c re te f i l l , 2 - s t e e l p l a t e . )

bottom o f a c a r u t y formed in th e to p o f th e f o o t in g as shown i n F ig u re

A column a l s o can be jo i n e d to i t s f o o t in g u s in g th e method t o

be seen i n F ig u re 3. In a l l t h r e e c a se s o f t h i s method, th e column

r e s t s on th e f o o t in g by a to n g u e - l i k e e x t e n s io n , t h e c r o s s - s e c t i o n o f

which i s r e l a t i v e l y s m a l l . In a) th e s t e e l b a r s a r e o v e r la p p in g , b)

hooked s t e e l b a r s a r e u s e d , and in c) t h e s t e e l b a r s a r e welded t o

g e th e r . ^

A column can be f ix e d i n t o i t s f o o t in g by lo o p -sh a p e d s t e e l b a r s

o f t h e main re in fo rc e m e n t p ro t r u d in g beyond th e low er end o f th e column2

i n t o a d e q u a te ly shaped h o le s i n th e fo o t in g as shown i n F ig u re 4.

A f i f t h method o f j o i n i n g a column to th e f o o t in g i s t o f a s t e n

th e column t o th e fo u n d a t io n by an ch o r in g b o l t s as i n F ig u re 5. Using

th e method shown in F ig u re 5A, a. cement m o r ta r i s p la c e d between th e to p

o f th e f o o t in g and th e s t e e l p l a t e on t h e bottom o f th e column. When

th e j o i n t as shown i n F ig u re 5B i s u se d , t h e u p p er s t e e l p l a t e , which i s

to be welded t o th e re in fo rc e m e n t o f th e column, shou ld be p u t on to th e2

low er s t e e l p l a t e and f a s t e n e d to th e an ch o r in g b o l t s . ,

In t h i s experim en t epoxy i s p roposed f o r c o n n e c t in g th e column

t o t h e f o o t i n g . The column i s i n s e r t e d i n t o a p re p a re d r e c e s s in th e

f o o t i n g . The dep th o f th e column i n s e r t i o n i n t o th e fo o t in g i s v a r i e d ,

t h r e e c a se s a r e t a k e n : 5 in c h e s , 10 in c h e s and 15 in c h e s . S tu d ie s w i l l

be made o f th e column r o t a t i o n a l e f f e c t s due t o e c c e n t r i c lo a d s , and

th e s e e f f e c t s w i l l be compared to a m o n o l i th ic c o lu m n -fo o tin g c o n n e c t io n .

The r e s u l t o f th e m o n o l i th ic c a s t c o n t r o l specim ens o f t h i s experim ent

T~~T

b.

• “ •1

a.Figure 2. Welded j o i n t o f column to fo o t in g .

(Temporary s u p p o r t : a) by a r e in f o r c e d - c o n c r e t e tongue p ro t ru d in g from th e column;b) by s e p a r a t e r e in f o r c e d - c o n c r e t e p o s t s ; 1 - in s i t u c o n c re te , 2 - w eld ing , 013 - s t e e l p l a t e , 4 - r e in f o r c e d - c o n c r e t e p o s t . )

a. b. c.

F igu re 3. J o in in g o f column to fo o t in g .

[by a) o v e r la p p in g s t e e l b a r s ; b) hooked s t e e l b a r s ; c) welded j o i n t . ]

SECTION

B

# *

# #

I I I I

T

L _ _ t —4 L J

BSECTION A-A SECTION B-B

F igu re 4. J o in in g o f column to fo o t in g by p ro t ru d in g loop-form ed s t e e l b a r s .

> )r^

F igu re 5. J o in in g o f column to f o o t in g b o l t s

00

w i l l be compared to t h e r e s u l t o f t h e "C onnec tions in P r e c a s t C oncre te

S tru c tu re s -C o lu m n Base P l a t e s " , which has been done by R. W. LaFraugh

and D. D. Magura o f th e P o r t la n d Cement A s s o c i a t i o n .&

Epoxy was chosen b ecau se i t has a v e ry h ig h com press ive s t r e n g t h ,

i t i s easy t o u s e , and i t s e t s i n a r e l a t i v e l y s h o r t t im e .

CHAPTER I I

DESIGN

A. The Column

1. Fixed o r d in a r y c o n n e c t io n : This column has b een d es ig n e d

by th e PCA a c c o rd in g to th e u l t i m a t e - s t r e n g t h method. In t h i s c h a p te r

th e d e s ig n has been checked .

The b a la n c e d c o n d i t io n in th e lo a d in g c o n d i t io n which p roduces

a t u l t i m a t e s t r e n g t h a s t r a i n o f .003 i n th e ex trem e f i b e r o f c o n c r e te ,3

and s im u l ta n e o u s ly , th e y i e l d s t r a i n in th e t e n s io n s t e e l , as shown i n

F ig u re 6.

The e c c e n t r i c i t y e^ i s m easured from th e p l a s t i c c e n t r o i d . The

p l a s t i c c e n t r o i d o f a s e c t i o n i s th e c e n t r o i d o f th e r e s i s t a n c e to load

computed from th e a ssum ptions t h a t th e c o n c re te i s s t r e s s e d u n ifo rm ly

t o 0 . 8 5 f ' and th e s t e e l i s s t r e s s u n ifo rm ly t o f as shown i n F ig u re 7.

For t h i s problem t h e c ro s s s e c t i o n , s t r a i n , and s t r e s s d iagram s

a r e shown i n F ig u re 8.

10

11

e = e b --------------

PLASTIC CENTROID

Pu = Pb

€ = —

STRAIN

F ig u re 6. S t r a i n o f th e e c c e n t r i c loaded column.

X

T = A s f y

F ig u re 7

ACTUAL S T R E S S DISTRIBUTION

Pu = P b

AVERAGE = . 85

a b z K | x b ^

Forces a c t in g on e c c e n t r i c loaded column

13

10'

JL

4 NO. 9

d ' = 2

f c = 5 KSI

f y = 5 0 KSI

NO. 3 AT 10 TIES

(ART. 8 0 6 ACI CODE)

8 . 2 7

STRAIN

h 7 . 5 —

- 6 . 6 2

T = 100

Jl

C s = 91 . 5

C c = 2 8 2

S T R E S S

ii

= 2 7 3 . 5

F ig u re 8. S t r e s s - s t r a i n o f th e m o n o l i th ic column.

14

To l o c a t e th e n e u t r a l a x i s .

8700 d xb f + 87000

y

87000 (13) _ . ,xb 50000 + 87000 in ches

a^ = = (0 .8 (8 .27 ) = 6 .62 i n .

The v a lu e i s to be ta k e n as 0 .8 f o r £ ' = 5000 p s i (ACI 1503 g)

To compute t h e f o r c e s C^, Cs> and T.

C = 0 .85 £ ' ab c c

Cc = 0 . 8 5 ( 5 ) ( 6 . 6 2 ) ( 1 0 ) = 282 k ip s

C = A' ( £ ' - 0 .85 f ) s s y c

Cs = 20 [50 - 0 .8 5 ( 5 ) ] = 91 .5 k ip s

T = A fs y

T = 50 (2) = 100 k ip s

P = C + C - T = 273.5 k ip sp c s r

_ 2 8 2 ( 7 . 5 - ^ 1 ) + 91 .5 (7 .5 - 2) + 100 (7 .5 - 2)P 'b = 12--------------------------------------------

= 186 f t - k i p s .

% " = 8 - 17 in c h e s

The a c t u a l e c c e n t r i c i t y o f t h i s column i s 14.75 in c h e s . T h e r e f o re , t h e

u l t i m a t e c a p a c i t y i s governed by t e n s i o n (Region I I I ) .

15

To compute th e l o c a t i o n and the v a lu e o f t h e P (F ig u re 8 ) .u

Cc = 0.85 (5) (0 .8x) 10 = 34x k ip s

Cs = 91 .5 k ip s

T = 100 k ip s

Force e q u i l i b r i u m r e q u i r e s

P = C + C - T = 34x - 8.5 u c s

Taking moments a r b i t r a r i l y about th e t e n s i o n s t e e l , r o t a t i o n a l e q u i l i b r i u m

g iv e s

pu (e - = Cc (d - | ) + Cs (d - d ' )

(34x - 8 .5 ) (14 .75 + % = 34x (13 - 0 .4x) + 91 .5 (11)

x = 3.94 inches

Cc = 34 (3 .94 ) = 134 k ip s

P = 134 - 8 .5 = 125.5 k ip su

Exact v a lu e s a r e used in t h i s e x p e r im en t , t h e r e f o r e 0 = 1 (0 = c a p a c i t y

r e d u c t i o n f a c t o r ) .

P u s a b l e = 0 P u u

= (1) (125 .5 ) = 125.5 k ip s

To check th e e f f e c t i v e l e n g th o f t h e column, h " in Eq. 9 .5 below i s

t a k e n as tw ic e t h e a c t u a l column l e n g th b eca use th e column i s f i x e d a t

one end and f r e e a t t h e o t h e r end.

16

R = 1.18 - .009 p - _< 1 (Eq. 9 .5 code)

R = 1.18 _ '009 (96)4 .5

= .998 < 1 No need f o r r e d u c t i o n .

To check th e u l t i m a t e s t r e n g t h o f t h e c o r b e l .*

d = 18 - 1 - -1—*-2-8. = 16.436

J = 1 0 3 6 = 0 -44

A + An _ s v 2.628 _ ,P " 16.436 X 10 -

vu = S) bd /F " f 1 f 2

Using Tab les 2 and 3 t o o b t a i n and F?

V = .85 x 10 x 16.436 /5000 (5 .15 ) (2 .52)u

= 130 k ip s 125.5 k ip s O.K.

*A c o r b e l i s a p r o j e c t i o n from t h e f a c e o f a column used in p r e c a s t c o n c r e t e c o n s t r u c t i o n t o s u p p o r t p r im ary beams and g i r d e r s .

PCA B u l l e t i n D85 was used in check ing t h e u l t i m a t e s t r e n g t h .

NO. 4 BARNO. 9 BAR

NO. 7 BAR

2 8 ^

17

4 8

r ~

4 NO. 3 TIES AT 10" C - C

4 NO. 9 BARS

4 8

Note: Foo t ing r e i n f o r c e d w i th #6 b a r a ta p p ro x im a te ly 6" c e n t e r s bo th d i r e c t i o n s in top and bottom l a y e r .

SECTION A - A

oFigure 9. Monolithic Column.

18

2. Epoxy ty p e c o n n e c t io n : This column was des igned t h e same as th em o n o l i t h i c . Three c a s e s have been ta ken (5 , 10, and 15 in c h e s ) t o i n v e s t i g a t e t h e u l t i m a t e c a p a c i t y o f each c o n n e c t io n . The b e a r i n g a r e a in t h e t e n s i o n s i d e o f t h e f o o t i n g v a r i e s d i r e c t l y w i th t h e dep th o f t h e column in t h e r e c e s s . F igu re 10 below.

NO. 4 BARNO. 9 BAR

NO. 7 BAR

28 2

10'

T YP E I = 5 3 T Y PE '2 ' = 5 8 "T Y P E '3 ' = 6 3

22

r "4 NO. 9 BARS

4 NO. 3 TIES 5 3 " AT 10" C - C

T Y P E V

T Y P E

T Y P E ' 3 SECTION A - A

Figure 10. Epoxy column.

19

B. The Footing

1. Fixed o r d i n a r y c o n n e c t i o n : This f o o t i n g has been des ig n ed by

th e PCA a c c o rd in g to t h e u l t i m a t e - s t r e n g t h method. In t h i s t h e s i s t h e

d e s ig n has been checked .

d = 10 - 2 .5 - .75 = 6.75

Pu = 125.5 k ip s

Vu = Pn e t (Area) = (7 .8 ) [4 (4) = ( i l i l i ) ] = 104 k ips

v _ Vu _ 104000 _u b Z ~ 2 (1 .8 6 + 1.44) 6 .75 P

Allowable V = 4 0 / P " (ACI 1707C) uc c

= 4 ( . 8 5 ) /5000 = 240 p s i s a t i s f a c t o r y

one-way a c t i o n

vu = 7 .8 ( ^ y ^ - ) 4 = 26 .7 k ip s

vu = n = = 8 2 *8 p s i

Allowable V = 2 0 / ? ^ (ACI 1701C) uc c

= 2 ( .8 5 ) / 5 0 0 0 = 120 p s i s a t i s f a c t o r y

Check t r a n s f e r o f s t r e s s a t t h e base o f th e column.

20

4 8

4 8

T10' NO. 6 AT 6 ±

10 + d = 17.25" = 1.44

15 + d = 2 2 . 2 5 " = 1.86'

gFigure 11. Monolithic Footing.

21

6 . 7 5 10 . 25

Allowable U = 1 3 /7 ^ u c (ACI 1801C3)

U = 13/5000 = 916 p s i u r

use 800 p s i

The com press ive f o r c e t o be t r a n s f e r r e d i s

Cu = f y As

Cu = 50(1) = 50 k ip s

The anchorage l e n g th needed i s

CL = u

Uu eo

50.000 ,( 8b o m V 54' ) = 17 - 5 lnCheS

The anchorage l e n g th s o f 12 inc hes and 31 inc hes in th e f o o t i n g .

V s a t i s f a c t o r y

Check bending moment. The c r i t i c a l s e c t i o n f o r moment i s a t t h e face

o f the column.

M

Mu = T

22

Mu - 1/2 (7 .8 ) (4) (IZ2I ) = 33 .3 f t - k i p s

Mu = = 37

( .8 5 ) (5 0 0 0 )4 8 =6(50000) 1.46 inch

C = .85 f ' bac

NT = (0 .85) (5000)(48) 1.46 [ 6 .7 5 - 0 .73 ] = 181 f t - k i p s > 3 7 f t - k i p sl

7 s a t i s f a c t o r y

Check f l e x u r a l bond.

Vu = Pn e t ba

Vu = ( 7 . 8 ) ( 4 ) ( 1 . 4 6 ) = 456 k ip s

,, _ u 456000 _ c n n ___ su = 0 £o j d = T O s T T s T F n O T T T O T T 500 p s i

Allowable U 9.s/fZu D

9.5/500&0.75 = 894 p s i s a t i s f a c t o r y

23

8 - NO. 6 BAR (SPACING = 6 " 1 )TOP AND BOTTOM LAYER

4 8

3" CLEAR COVER

- 4 8" -

eF igu re 12. M o n o l i t h ic f o o t i n g d e t a i l s .

24

2. Epoxy ty p e c o n n e c t i o n : The t h r e e ty p e s o f f o o t i n g d es ig n d e t a i l sshown in F igu re 13 below a r e f o r t h e t h r e e columns shown in F igu re 10.

8 NO. 6 BAR SPACING = 6 " ± TOP AND BOTTOM LAYER

10% 4 8

I NO. 4 TIES

TYPE I = 10 DEPTH TYP E 2 = 15" DEPTH TYPE 3 = 2 0 " DEP TH

15 % 3" CLEAR COVER1 8 -

T Y P E

| T Y P E 2 20T Y P E 3

4 8 "

Figure 13. Epoxy Footing,

CHAPTER III

NATURE AND SCOPE OF TESTS

The u l t i m a t e s t r e n g t h o f t h e u n i t may be reac hed i n one o f t h e s e

ma jo r ways .

1. The column may f a i l i n t e n s i o n b e f o r e any y i e l d i n g t a k e s

p l a c e i n t h e c o n n e c t io n .

2. The t e n s i o n s i d e o f t h e column i n t h e r e c e s s and t h e t e n s i o n

s i d e o f t h e r e c e s s may y i e l d b e f o r e column s t r e n g t h i s

r eac h ed .

Premature f a i l u r e o r d i s t r e s s unde r s e r v i c e lo ads may r e s u l t

from f a u l t s i n f a b r i c a t i o n o f p r e c a s t members, and d e f e c t s i n g lu i n g .

I n s t r u m e n t a t i o n and T e s t Equipment

A t y p i c a l t e s t s e t - u p i s shown i n F ig u re 14. Load was a p p l i e d

t o t h e to p o f t h e column by means o f a 15 - inch s t e e l I beam and two

Re-Mo-Trol h y d r a u l i c rams o f 50 to n s c a p a c i t y spaced a t 3 0 - i n c h e s , as

shown i n F ig u re 15. The rams were s u p p o r te d by a 1 5 - inc h s t e e l I beam

i n t h e basement o f t h e l a b o r a t o r y . The f o o t i n g was f i x e d r i g i d l y t o t h e

l a b o r a t o r y f l o o r by f o u r s t e e l beams f a s t e n e d t o t h e basement f l o o r by

f o u r rods o f 1 - in c h d i a m e te r . Nuts on th e rods below t h e basement f l o o r ,

and on t h e to p o f t h e s t e e l beams p r o v id e d a n c h o ra g e . The s t e e l I beam

which s u p p o r te d t h e rams p u l l e d by two 1 - 1 / 2 - i n c h d i a m e te r r o d s , spaced

a t 6 - f e e t , pa s s ed th rough openings i n t h e f l o o r up t o and th rough t h e

25

Figu re 14. T es t Arrangement

It> <f> S T E E L ROD

AND NUTS

15 INCH S T E E L I BEAM

- P L A S T E R

COLUMN

S T E E L BEAM

FOOTING

LABORATORY FLOOR

HYDRAULIC RAMS

15 INCH S T E E L BEAM

Figure 15. Test Setup Instrumentation.

F ig u re 16. Gauges f o r Measur ing D e f l e c t i o n s

29c r b s s h e a d . Nuts on t h e rods below t h e s t e e l beam in t h e ba s e m e n t , and

on t h e t o p o f t h e c ro s s h e a d p ro v id e d anchorage .

The two 1 -1 /2 inc h rods were f r e e t o r o t a t e w i th d e f l e c t i o n o f

t h e column. A 1/2 in ch Hydrocal p l a s t e r l a y e r was p l a c e d on t h e to p o f

t h e column unde r t h e c ro s s h e a d t o d i s t r i b u t e t h e load u n i fo rm ly t o t h e

C orbe l . The c r o s s s e c t i o n o f t h e t e s t s e t - u p i s shown i n F ig u re 15.

H o r i z o n t a l d i s p la c e m e n ts o f t h e specimens were measured a t f i v e

l o c a t i o n s on t h e t e n s i o n s i d e o f t h e column by Lufkin gauges (0.0001

inch s e n s i t i v i t y ) . I n d i v i d u a l Lufk in gauges were p o s i t i o n e d 6, 12 and

18 in c h es and t h r e e a t 46 in c h es above t h e to p o f t h e f o o t i n g . They

were s u p p o r te d on a r i g i d s t e e l framework g lued by epoxy t o t h e to p o f

t h e f o o t i n g . A s c a l e was a t t a c h e d t o t h e s i d e o f t h e framework n e a r t h e

to p o f t h e column and was r e f e r e n c e d t o a s t a t i o n a r y p o i n t t o measure

d e f l e c t i o n a f t e r t h e r ange o f t h e mechan ica l d i a l gauges was e x h a u s te d .

The gauges a r e shown i n F ig u re 16.

Colum n-foo ting Connect ion

The epoxy co lu m n - fo o t in g c o n n e c t io n , l i k e a l l s t r u c t u r a l members

o f a p r e c a s t c o n c r e t e b u i l d i n g , must s a t i s f y s e r v i c e a b i l i t y and s t r e n g t h

r e q u i r e m e n t s . G e n e r a l l y , t h e r e s t r a i n t c o n d i t i o n a t t h e c o lu m n - fo o t in g

j u n c t i o n i s r e g a rd e d as f i x e d o r p in n e d . The r i g i d i t y o f t h e epoxy

c o lu m n - fo o t in g c o n n e c t io n i s dependent on t h e dep th o f t h e r e c e s s i n t h e

f o o t i n g and t h e f l e x i b i l i t y o f t h e epoxy.

Depths o f r e c e s s were chosen on t h e f o l l o w in g b a s i s :

1. F i f t e e n i n c h , r e c e s s . This dep th approx im ate s S o v ie t

p r a c t i c e , and was e xpec ted t o behave as t h e m o n o l i t h i c u n i t .

I t i s a l s o t h e same as t h e l e n g th o f t h e lo n g e r s i d e o f t h e

30

column, t h e r e f o r e has a g e o m e t r i c a l b a s i s f o r c o n s i d e r

a t i o n .

2. Ten in ch r e c e s s . This has a b a s i s i n column geometry and

i s midway between th e d e e p e s t and th e s h a l l o w e s t r e c e s s e s ,

and t h e r e f o r e , was expec ted t o have a d eg ree o f r i g i d i t y

between th e two.

3. F ive in c h r e c e s s . Thi s dep th was chosen on t h e b a s i s o f

s t e e l dep th i n t h e column and t h e f o o t i n g . Minimum s t e e l

c o v e r in g d i c t a t e d a dep th o f f o u r inches f o r column end

s t e e l and f o o t i n g to p s t e e l t o l i e i n t h e same p l a n e . How

e v e r , t h i s was no t c o n s id e r e d to be adequa te d e s ig n and an

a d d i t i o n a l inch;was p ro v id e d .

0

CHAPTER IV

TEST RESULTS

The e c c e n t r i c i t y i n c r e a s e d due to specimen de fo rm a t io n as t h e

column load was a p p l i e d . Moments a c t i n g on t h e column b ase were taken

as t h e p ro d u c t o f t h e measured load and t h e i n i t i a l e c c e n t r i c i t y p lu s

t h e change in e c c e n t r i c i t y , e + Ae. The measured d e f l e c t i o n a t t h e to p

o f t h e column was used t o compute change i n column load e c c e n t r i c i t y a t

t h e column b a s e . As shown in F igu re 17, t h e column to p moved l a t e r a l l y

P P + A P

A C = 0 . 1 7 8 6

Figure 17. Load Eccentricity.

31

32

an amount 6 due t o specimen d e fo rm a t io n when t h e load was i n c r e a s e d by

AP. The to p o f t h e f o o t i n g was assumed t o remain p l a n e , and th e

e c c e n t r i c i t y , Ae, a t t h a t l e v e l was computed from geometry t o be equa l

t o 0 .1786 .

Moment -Rotat ion C h a r a c t e r i s t i c s

The m o m e n t - ro ta t io n c h a r a c t e r i s t i c s o f t h e specimens a r e p l o t t e d

i n F ig u re s 19, 20, 21, and 22 t o show t h e e f f e c t s o f t e s t v a r i a b l e s .

The i n i t i a l load e c c e n t r i c i t y f o r t h e specimens shown was 14.75 in c h .

An a r b i t r a r y i n d i c a t i o n o f r o t a t i o n o f t h e specimens was de te rm ined from

t h e d i f f e r e n c e in l a t e r a l d e f l e c t i o n o f t h e column measured a t 46 inc hes

above t h e to p o f t h e f o o t i n g . The moment- r o t a t ion c h a r a c t e r i s t i c s o f

t h e fo u r specimens and th e PCA m o n o l i t h i c specimen a r e shown i n F ig u re

23. Note t h a t t h e PCA m o n o l i t h i c d a t a has been e x t r a p o l a t e d from p o i n t

1 t o p o i n t 2, and t h e 15 inc h dep th c o n n e c t io n d a t a e x t r a p o l a t e d from

p o i n t 3 t o p o i n t 4 i n o r d e r t h a t compari son o f t h e u l t i m a t e r e g i o n o f

t h e curves may be made. Th is i s j u s t i f i e d on t h e b a s i s o f t h e mode o f

y i e l d i n g .

In t h e e a r l y s t a g e s o f lo a d in g , t h e specimens e x h i b i t e d n e a r l y

l i n e a r m o m e n t - ro ta t io n c h a r a c t e r i s t i c s . As y i e l d i n g o c c u r r e d i n t h e

t e n s i o n s i d e o f t h e column and t h e r e c e s s , th e r a t e o f r o t a t i o n in c r e a s e d

w i th moment and t h e cu rves became n o n - l i n e a r . There i s a d i f f e r e n c e

be tween t h e m o m e n t - ro ta t io n c h a r a c t e r i s t i c s cu rves due t o t h e e l e v a t i o n

o f t h e gauges i n a l l specimens and t h a t i s n a t u r a l b ecause as t h e columns

c r a c k e d , i n d i v i d u a l segments r o t a t e d as shown i n F ig u re 24. The 5 inch ■

33

depth r e c e s s f a i l e d c a t a s t r o p h i c a l l y , and a small p o r t i o n o f t h e t e n s i o n

s i d e came out as shown in F igu re 25. The r e a s o n t h e v e r t i c a l t e n s i o n

s i d e o f the r e c e s s d id no t f a i l was b eca use t h e depth o f th e r e c e s s was

ve ry sha l low i n comparison t o t h e l a t e r a l d imension . The 10 inch depth

column, a l s o f a i l e d c a t a s t r o p h i c a l l y , bu t a l l o f t h e v e r t i c a l t e n s i o n

s i d e o f t h e f o o t i n g came o u t , as shown i n F igu re 26. The r e a s o n f o r t h e

f o o t i n g t e n s i o n f a i l u r e was t h a t th e column has enough dep th t o be f i x e d .

This i s d i s c u s s e d in more d e t a i l i n t h e nex t c h a p t e r . The 15 inch dep th

u n i t f a i l e d in t h e mode o f t h e m o n o l i t h i c u n i t , t h a t i s , column t e n s i o n

f a i l u r e , w i th no a p p a re n t d i s t r e s s t o t h e f o o t i n g t h e r e b y p e r m i t t i n g

f a v o r a b l e compar ison w i th t h e m o n o l i t h i c u n i t .

Column s t i f f n e s s M/0 computed from t h e m o n o l i t h i c and p r e c a s t

specimens as shown in F igu re 18 below.

<P

F igu re 18. Column r o t a t i o n .

34

The s t i f f n e s s M/0 i s a measure o f l i n e a r r e s p o n s e . Table I shows th e

s t i f f n e s s v a lu e s as computed from F igu res 23 and 32.

Tab le I . S t i f f n e s s Values .

Specimens M/0 10^ i n . k i p s / r a d i a n s

5 i n . dep th Column 362



M o n o l i t h ic 480

PCA M o n o l i t h ic 510

T h e o r e t i c a l 530

APPLIE

D

MO

ME

NT

, M,

inch -K

IPS

2 4 0 0

2000

6 0 0

GAGE I ( 6 in FROM TOP OF FOOTING) GAGE 2 (12 in FROM TOP OF FOOTING)

GAGE 3 (18 in FROM TOP OF FOOTING)


1200 r

8 0 0

4 0 0

4 8 6 4 8 0 128 144 16016 3 2 9 6 1120

COLUMN ROTATION <f>, I 0 " 5 RADIANS

F ig u re 19. M-0 b e h a v io r o f th e m o n o l i th ic u n i t .

APP

LIED

M

OM

EN

T,

M,

inch

-

KIP

S

36

2 0 0

8 0 0 -

4 0 0 -

GAGE I (6 in FROM TOP

OF FOOTING) GAGE 2 (12 in FROM TOP

OF FOOTING) GAGE 3 (18 in FROM TOP

OF FOOTING)

GAGE 4 ( 4 6 in FROM TOP OF FOOTI NG)

0 4 8 16

COLUMN ROTATION <#>, I 0 ' 5 RADIANS

Figure 20. M-0 behavior of the 5 inch depth unit.

APP

LIED

M

OM

ENT

, M,

in

ch-K

IPS

37

2000

1 6 0 0 -

1200 -

8 0 0 -

4 0 0 -

GAGE I ( 6 in FROM TOP OF FOOTING)


GAGE 3 (18 in FROM TOP

OF FOOTING)

GAGE 4 ( 4 6 in FROM TOP OF FOOTING)

0 4 8 16

COLUMN ROTATION I 0 ~ 5 RADIANS

Figure 21. M-0 behavior of the 10 inch depth unit

APPLIE

D

MO

ME

NT

, M

, in

ch-KIP

S

2 4 0 0

2000

1 6 0 0

• GAGE I (6 in FROM TOP OF FOOTING)o GAGE 2 (12 in FROM TOP OF FOOTING)

□ GAGE 3 (18 in FROM TOP OF FOOTING)

a GAGE 4 ( 4 6 in FROM TOP OF FOOTING)

1200

8 0 0

4 0 0

0 16 3 2 4 8 6 4 8 0 9 6 112

COLUMN ROTATION </>, I 0 “ 5 RADIANSF igu re 22. M-0 b e h a v io r o f th e 15 inch depth u n i t .

d e p t h

1 in15

° 10 in

'n DEPTHO ,K . DEPTH

M o h o u t h i c

P C A ^ o u

* 3 2 1

UnitS M'0 be0,favti oer.m° noJj

— -U _6 4

/ 0 ' 58 0 96

thi , PCA Monoii thi ,10

40

15 inch dep th column 10 inch dep th column

M o n o li th ic Column

F igu re 24. Modes o f F a i l u r e

41

F ig u re 25. 5 Inch Depth Recess F a i lu r e

Figure 26. 10 Inch Depth Recess Failure

CHAPTER V

ANALYSIS OF TEST RESULTS AND RECOMMENDATIONS

The b e h a v io r o f th e c o lu m n -fo o tin g c o n n e c t io n specim ens i s

c h a r a c t e r i z e d by two d i s t i n c t p h a s e s - - th e l i n e a r re sp o n se to load

where a l l s t e e l and c o n c re te as w e ll as epoxy behave e l a s t i c a l l y and

th e n o n - l i n e a r re sp o n se to load i n t i a t e d by y i e ld in g in th e column o r

c o n n e c t io n . The co n n e c t io n s t i f f n e s s , i . e . th e m o m en t-ro ta t io n

r e l a t i o n s h i p M/0, i s a measure o f th e l i n e a r re sp o n se to lo ad . The

column load a t which th e r a t e o f r o t a t i o n b eg in s to in c r e a s e depends

on th e s t r e n g t h o f th e c o n n e c t io n .

In a p r e c a s t b u i l d i n g , d i s t r i b u t i o n o f s e r v i c e loads w i l l depend

on member s t i f f n e s s and th e m o m en t- ro ta t io n c h a r a c t e r i s t i c s . The column-

fo o t in g c o n n e c t io n s t i f f n e s s , M/0, must be computed.

The maximum moment p e rc e n ta g e i s a m easure o f th e n o n - l i n e a r

re sp o n se to lo ad . This maximum moment p e rc e n ta g e i s th e r a t i o o f th e

maximum moment o f each column to th e maximum moment o f th e m o n o l i th ic

u n i t shown in T ab le I I .

T ab le I I . Moment P e rcen tag e

Specimens % Maximum Moment

5 - in ch depth -5 6 .6 2

10- in c h depth -1 2 .7 8

15- in ch depth + 4.819

T h e o r e t i c a l - 1.414

42

43

Assuming th e m o n o l i th ic u n i t to be 100% f ix e d and a p in

co n n e c t io n as 0% f ix e d , i t was found t h a t th e 15 inch dep th was f u l l y

f ix e d and th e 5 inch and 10 inch dep ths p a r t i a l l y f ix e d . T h is i s shown

in T ab le I and I I .

The coup led fo r c e system a p p l ie d to th e r e c e s s by th e column o f

any o f th e t e s t specim ens w i l l rem ain c o n s ta n t f o r a p a r t i c u l a r load

because o f th e geometry o f lo a d in g . The h o r i z o n t a l r e s i s t i n g fo rc e fo r

th e s h o r t e s t moment arm has to be l a r g e r th an t h a t f o r th e g r e a t e s t

moment arm. This i s shown d ia g ra m m a t ic a l ly in F ig u re 27 below. Because

P3 a

P P 3

M = Pa M = 3 a

Figure 27. Effect of moment arm on the resultant forces.

44

o f th e above r e a s o n th e 5 - in c h dep th r e c e s s f a i l e d c a t a s t r o p h i c a l l y

w ith a sm all amount o f moment. The 1 0 - inch r e c e s s a l s o f a i l e d

c a t a s t r o p h i c a l l y b u t w ith more moment load however a t 1 5 - in ch dep th

t h e column f a i l e d b e f o r e t h e r e was any y i e l d i n g in th e c o n n e c t io n .

Comparing th e m o m e n t- ro ta t io n r e l a t i o n s h i p between th e p r e c a s t

u n i t s and th e m o n o l i th ic i n F ig u re 23, i t i s shown c l e a r l y t h a t th e

s lo p e o f th e l i n e a r re sp o n se o f th e p r e c a s t u n i t s i s l e s s th a n th e s lo p e

o f th e m o n o l i th ic u n i t . That i s b ecau se th e modulus o f e l a s t i c i t y , E,

in th e epoxy i s 350,000 p s i which i s much l e s s th a n c o n c r e te , (4 ,0 0 0 ,0 0 0

p s i ) p e r m i t t i n g r o t a t i o n i n t h e r e c e s s . R o ta t io n o f th e p r e c a s t u n i t i n

th e r e c e s s b eg in s w ith a p p l i c a t i o n o f load and c o n t in u a n c e i n a l i n e a r

re sp o n s e up t o 1,950 in c h -k ip s where t h e r e i s an a b ru p t change t o n e a r l y

h o r i z o n t a l r e sp o n s e as u n i t s t a r t s t o f a i l . The l i n e a r i t y in th e mono

l i t h i c u n i t p e rm i ts up t o 800 in c h -k ip s where th e n o n - l i n e a r re sp o n se

d ev e lo p in g to about 1800 i n c h - k i p s , th e n th e re sp o n se becomes n e a r l y

h o r i z o n t a l .

Comparing th e cu rv es in F ig u re s 28, 29, 30, and 31, i t i s shown

t h a t th e 1 5 - in ch d ep th column has th e same mode o f f a i l u r e as th e mono

l i t h i c , m oreover th e m o n o l i th ic f a i l e d a t 1909 in c h -k ip s w h ile th e 15-

inch d ep th f a i l e d a t 2001 in c h - k ip s . The 5, and 1 0 - in ch dep th f a i l e d

su d d e n ly , as shown, a t 828 and 1665 in c h - k i p s , r e s p e c t i v e l y .

F ig u re 32 shows th e m o m e n t- ro ta t io n c h a r a c t e r i s t i c s f o r th e

t h e o r t i c a l , m o n o l i th ic and 15 - in ch dep th column. T h is c u tv e shows t h a t

th e t h e o r e t i c a l and th e m o n o l i th ic cu rv es have th e same s lo p e up to 800

i n c h - k i p s , where t h e m o n o l i th ic u n i t d e p a r t s from l i n e a r i t y . The s lo p e

o f th e p r e c a s t u n i t cu rv e i s l e s s th a n b o th o f th e s e s lo p e s .

451 8 0 0 i n - K

oo

C \J

1 6 0 0 in-K co

in

1 4 0 0 in-K

2 0 0 in- K

n-K10008 0 0 n-K

6 0 0 n-K

4 0 0 n-K

2 0 0 in-K

oo

ELEVATION OF THE GAGES FROM THE TOP OF THE FOOTING (in)

Figure 28. Elevation of the gauges - 0 behavior of the monolithic unit.

COLUMN

ROTA

TION

<#\

10 u

RA

DIA

NS


mm roo OD

2 0 0 i n - K

4 0 0 in -K

6 0 0 i n - K

8 0 0 i n - K

oo

Figure 29. Elevation of the gauges - behavior of the 5 inch depth unit. c-.

COLUMN

ROTA

TION

<#>,

10 u

RA

DIA

NS


- - £o m no oo cn

2 0 0 i n - K 4 0 0 i n - K

6 0 0 i n - K

8 0 0 i n - K

1 0 0 0 i n - K

2 0 0 in - K

1 4 0 0 i n - K

16 0 0 i n - K

00

Figure 30. Elevation of the gauges - (8 behavior of the 10 inch depth unit.

482 0 0 0 in- K \u>

m

1 8 0 0 in-K

1 6 0 0 n-K

1 4 0 0 n-K

120010008 0 0

n-Kn-Kn-K

6 0 0 n-K

4 0 0 n-K

200 n-K

Ooo CXJ— -


F ig u re 31. E le v a t io n o f th e gauges - 0 b e h a v io r o f th e 15 inch depth u n i t .

APPLIED

M

OM

EN

T,

M,

inch -

KIPS

2 4 0 0

2000

1 6 0 0

200 • THEORETICAL o 15 inch DEPTH

A MONOLITHIC

8 0 0

4 0 0

0 16 3 2 4 8 6 4 8 0 9 6 112 128 144 160

COLUMN ROTATION <f>, I 0 ' 5 RADIANSto

Figure 32. Comparison of the monolithic, 15 inch depth and the theoretical M - 0 behavior.

50

The re s p o n s e o f th e m o n o l i th ic u n i t compared f a v o ra b ly w ith

t h e t h e o r e t i c a l a n a l y s i s , t h e sm all d e p a r tu r e s a r e a t t r i b u t e d to s l i g h t

d i f f e r e n c e s in s t r e n g t h s o f c o n c re te and s t e e l . The re sp o n se o f th e 15

in c h dep th u n i t compared w e l l w ith b o th .

The r e s u l t s o f t h i s s tu d y compared f a v o ra b ly w ith t h e P o r t la n d

Cement A s s o c ia t io n s tu d y f o r th e column b a s e p l a t e s c o n n e c t io n s .

Recommendations f o r F u r th e r R esearch

T his method o f connecti 'ng f o o t in g and column i s p ro m is in g and i t

i s s u g g e s te d t h a t th e fo l lo w in g a d d i t i o n a l r e s e a r c h be done:

1. Find th e optimum d ep th o f r e c e s s betw een 10 and 15-inch.

d ep th such t h a t th e fo o t in g and column f a i l s im u l ta n e o u s ly

o r i n th e mode o f th e m o n o l i th ic u n i t .

2. The s t e e l in th e fo o t in g sh o u ld be d e s ig n ed t o i n c o r p o r a te

s t e e l a round th e r e c e s s . Three c o n f ig u r a t io n s a r e s u g g e s te d

in o r d e r o f d e c r e a s in g p rom ise .

a . V e r t i c a l s t e e l a d j a c e n t t o th e r e c e s s .

b . I n c l i n e d s t e e l from th e to p o f th e r e c e s s a d j a c e n t to

th e open ing o f th e bottom s t e e l .

c . C i r c u m f e r e n t i a l s t e e l a round th e r e c e s s .

A d e s ig n f o r t h e s e c o n f ig u r a t io n s i s beyond th e scope o f t h i s p a p e r .

APPENDIX

M a te r i a l s and F a b r ic a t io n

The wooden c o n c re te forms were made o f 3/4 inch plywood coa ted

w ith a t h i n f i lm o f o i l on th e i n s i d e , and r e in f o r c e d by tw is t e d t i e

w ire s from s id e to s id e as shown in F ig u re A. The c o n c re te used in a l l

columns and f o o t in g s was made w ith Type I P o r t la n d cement. Cast members

were cured under p l a s t i c covered wet b u r la p sacks f o r 28 d ays . The

av e rag e com press ive s t r e n g t h s a t th e t im e o f t e s t l i s t e d in T ab le A1

were d e te rm in ed from a minimum o f f i v e 6X12 inch c y l i n d e r s .

T ab le A1. Column and Foo ting C oncre te S t r e n g th

Specimen f c p s i E , p s i

M o n o li th ic Column 4991 4 ,0 7 0 ,0 0 0

M o n o li th ic Foo ting 5888 4 ,4 2 0 ,0 0 0

5 i n . dep th Column 5769 4 ,3 8 0 ,0 0 0

5 i n . d ep th F ooting 5840 4 ,410 ,000

10 in . dep th Column 6017 4 ,4 8 0 ,0 0 0

10 in . dep th F oo ting 5805 4 ,4 0 0 ,0 0 0

15 in . dep th Column 6194 4 ,5 4 0 ,0 0 0

15 in . dep th Footing 5699 4 ,3 5 0 ,0 0 0

I n te r m e d ia te g rade r e i n f o r c i n g s t e e l w ith d e fo rm a tio n s conforming

to ASTMA 305 was used in th e columns and f o o t i n g s .

51

Figure A. Precast Column and Footing Steel

53

The C elanese R esin Company produced th e epoxy which was used in

j o i n in g th e p r e c a s t members. The epoxy was mixed o f 100 p a r t s by w eigh t

o f Epi-Rez 510 to 35 p a r t s by w eigh t o f Ep i-C ure 872. The fo rm er i s

composed o f commercial d i g l y c i d a l e t h e r o f b is p h e n l A, c o n ta in in g no

added d i l u e n t s , s o lv e n t s o r o th e r c o n ta m in a n ts . The l a t t e r i s a

f l e x i b i l i z e r - h a r d e n e r composed o f an a l i p h a t i c amido polyam ine c o n s i s t i n g

o f th e r e a c t i o n p ro d u c t o f a long ch a in monobasic a c id w ith polyam ine and

a m o d if ied a l i p h a t i c p o ly am in e .^ The epoxy was cu red a t 80°F. The

av e rag e com press ive s t r e n g t h s a t th e tim e o f t e s t l i s t e d in T ab le All

were d e te rm in e d from a minimum o f s i x 1X2 inch c y l i n d e r s .

T ab le A l l . Epoxy S tr e n g th

SpecimenCompressive

S t r e n g th (p s i ) No. o f Curing Days

5 in . dep th 12783 7 days c u r in g a t 80°F

10 i n . dep th 14860 12 days c u r in g a t 80°F

15 in . dep th 14800 15 days c u r in g a t 80°F

The c o n f ig u r a t io n o f th e columns and f o o t in g i s shown in F ig u re s

9 , 10, 12 and 13. D e ta i l s o f r e in fo rc e m e n t in th e Corbel b r a c k e t s

th rough which load was a p p l ie d were th e same f o r a l l specim ens in t h i s

ex p e r im en t . The column re in fo rc e m e n t was a l s o i d e n t i c a l f o r a l l s p e c i

mens. The amount o f s t e e l in th e f o o t in g s was th e same, b u t th e v e r t i c a l

s e p a r a t i o n between to p and bottom s t e e l v a r i e d w ith fo o t in g d e p th , as

shown in F ig u re 13.

54

The m o n o l i th ic c o n t r o l specim en was c a s t w ith th e column in a

v e r t i c a l p o s i t i o n above th e f o o t i n g , t h e f o o t in g b e in g c a s t 5 days p r i o r

to th e column. The rem ain ing columns were c a s t in a h o r i z o n t a l p o s i t i o n

as shown in F ig u re Al. Column and f o o t in g r e in fo rc e m e n t was h e ld in

p la c e v e r t i c a l l y by th e t i e w ire s which r e i n f o r c e d th e fo rm s .

P r e c a s t columns were 53, 58, and 63 inch long measured from t h e i r

to p s u r f a c e to t h e bo ttom s u r f a c e o f th e column. P r e c a s t f o o t in g s

c o n ta in e d 5 - 1 /2 , 1 0 -1 /2 , and 15-1 /2 in c h r e c e s s e s formed by plywood

b o x e s , 15 -1 /2 by. 10 -1 /2 in c h e s i n p la n d im e n s io n s .

A f t e r c u r in g and removal from fo rm s , th e r e c e s s e s and b ases o f

th e columns were c le a n e d w ith 10% h y d r o c h lo r i c a c i d , f lu s h e d w ith w a te r

and d r i e d w ith com pressed a i r . Four s t e e l sh im s , 1X1X1/2 in c h e s , were

p la c e d in th e bo ttom c o m e r s o f th e r e c e s s e s . The s h o r t e s t column was

p la c e d in th e s h a l lo w e s t r e c e s s and th e lo n g e s t column i n th e d e e p e s t

r e c e s s .

A c o n s ta n t 48 inch d i s t a n c e from th e to p o f th e column t o th e

to p o f th e f o o t in g was m a in ta in e d .

S t e e l shims were u sed t o f a c i l i t a t e a l ig n m en t o f th e columns

and p ro v id e sp ace f o r epoxy. L a t e r a l a l ig n m en t was ach iev ed w ith t h i n

s t e e l wedges which were th e n removed and r e p la c e d by s t e e l shims p r i o r

t o p o u r in g th e epoxy .

55

P re c a s t U n its

M o n o li th ic S t e e l

Figure A1

REFERENCES

1. I n t e r n a t i o n a l Congress o f th e C oncre te I n d u s t r y , 3 rd , S tockholm ,1960.

2. P r e f a b r i c a t e d C o n c re te , Lhszld Mokk, B udapes t , 1964.

3. The Magic Powder, by E a r l J„ H adley.

4. The C hem istry o f Cement and C o n c re te , F. M. Lea § C. H. Desch.

5. R e in fo rc ed C oncre te D esign , C hu-k ia Wang § C h a r le s G. Salmon.

6 . F in a l R eport No. 2 to t h e A rizona Highway Department on th e Useo f Epoxy R esins i n R e in fo rc ed C o n c r e t e - S t a t i c Load T e s t s .P a r t I I , by J . D. Kriegh and E. G. Endebrock.

7. P o r t la n d Cement A s s o c ia t io n B u l l e t i n DBS, "C onnec tions i n P r e c a s tC oncre te S t r u c t u r e s - S t r e n g t h o f C o rb ie s " , by L. B. K riz andC. H. P a t h s .

8 . P o r t la n d Cement A s s o c ia t io n B u l l e t i n DUO, "C onnec tions in P r e c a s tC oncre te S tru c tu re s -C o lu m n Base P l a t e s " , by R. W. LaFraugh andD. D. Magura.

56

precast concrete column and footing...

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