"EFFECTIVENESS OF OVERLAPPING HOOPS AS DUCTILITY REINFORCEMENT IN SHORT REINFORCED CONCRETE COLUMNS"
"EFFECTIVENESS OF OVERLAPPING HOOPS AS DUCTILITY REINFORCEMENT IN SHORT REINFORCED CONCRETE COLUMNS"
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Date
1992-09
Authors
YA'U, Alhaji Sanusi,
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Abstract
Comparative study of the effectiveness of some typica l
arrangements of overlapping hoops to ordinary rectangula r hoop was
carrie d out. The overlapping arrangements were:-
Diamond Shape; Singl e Crossing; and Double Crossing (See appendix).
During th e study, a fixed stirru p spacing of 300mm (Model Size
120mm) and concret e - grade of 25 was used in al l the specimen.
Twenty four (24) specimens were prepared for this research with each
arrangement (Ordinary rectangula r hoop, Diamond shape, signl e
crossing and Double crossing) having six (6) specimen.
The concret e mix used in this experiment was designed to have
a rati o of 1:1%:3 and a grade of 25 with water-cement rati o of
0.7 (w/c = 0.7). Mixing of this concret e was done manually using
a dry batching process. The compaction of the cast specimens was
by stamping internally , while poker-vibrato r was used on the
surface , for proper dense settlement of the mixed concrete .
Measurements of stresse s and - strain s of the specimens under
loading was carrie d out with a strai n meter. The use of strain -
meter was possibl e through the hel p of STRAIN-GAUGES which were
soldered on the reinforcement - bars at four (4) differen t
position s (top front top-back, middle fron t and middle-back).
These strain-gauge s were also connected to a very thi n long and
flexibl e electroni c wire s by use of Araldit e glue .
The testin g of th e prepared specimens was carrie d ou t using
UNIVERSAL TESTING MACHINE. Care was taken in ensuring proper place -
ments of th e specimens on the machine before loading, in orde r to
avoid excessive eccentri c loading on the specimens. The loading
of al l the teste d specimens was a gradual process, while the
readings of interna l stresse s and strain s of the specimens were recorde d a t some interva l differen t loadings, wit h th e ai d o f a
STRAIN METER.
Using th e recorde d result s o f th e Specimens, "STRESS-STRAIN
CURVES" wer e drawn i n orde r t o determin e th e ductilit y o f each -
o f th e arrangements unde r study . I n theory , th e ductilit y o f a
confine d concret e is determine d b y measurin g and computing th e angl e
o f slop e o f th e descendin g par t o f it' s 'STRESS-STRAIN CURVE.' The
more acut e th e angl e o f th e descendin g par t o f th e curve , th e more
ductil e is th e confine d concrete .
I t was observe d tha t i n al l th e case s o f th e Specimen
loadings, th e stee l starte d yieldin g befor e th e ultimat e loa d was
reached . Thus n o reading s wer e obtaine d fo r highe r loads. Also
some o f th e Strain-Gauge s wer e found t o b e faulty .
I t was als o observe d tha t th e failur e was eithe r a t th e to p
o r th e bottom o f th e teste d Specimen. No column was abl e t o carr y
highe r loa d afte r spallin g o f concret e began .
As a check t o th e result s o f th e teste d specimens, both
tensil e and - compressiv e strength s wer e carrie d ou t o n prepare d
sample s o f th e material s o f th e specimen s used . Tensil e tes t was
carrie d ou t o n stee l - samples, whil e compressive-test was done o n
t h e concret e cubes.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL, AHMADU BELLO
UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF REQUIREMENTS FOR THE
DEGREE OF MASTER OF SCIENCE IN CIVIL ENGINEERING (STRUCTURES).
DEPARTMENT OF CIVIL ENGINEERING
AHMADU BELLO UNIVERSITY
ZARIA
NIGERIA.
SEPTEMBER, 1992.
Keywords
"EFFECTIVENESS,, OVERLAPPING,, HOOPS,, DUCTILITY,, REINFORCEMENT,, SHORT REINFORCED CONCRETE COLUMNS"