“EFFECTIVENESS OF OVERLAPPING HOOPS AS DUCTILITY REINFORCEMENT IN SHORT REINFORCED CONCRETE COLUMNS” » Download Project Topics

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

“EFFECTIVENESS OF OVERLAPPING HOOPS AS DUCTILITY REINFORCEMENT IN SHORT REINFORCED CONCRETE COLUMNS”