Behavior of Spirally Deformed Bars in Slabs

Experimental program was carried out at the University of Texas at San Antonio to study the flexure and splice behavior of high strength spirally deformed reinforcing bar in slab construction. Performance of spirally deformed bars was compared with that of traditional deformed Grade 60 reinforcing bars. Spiral bars (0.113 in.2, 0.071 in.2 and 0.068 in.2) with three different effective areas were under investigation. All flexure test were tested with one point load setup whereas the splices test were subjected to two point load setup. Load was applied by the ram until the specimen failed or was out of stroke. Test parameters were reinforcement type, amount of reinforcement, diameter of reinforcing bar, and splice length. Conclusions were drawn that ACI 318-14 moment computation methods can be used for spiral bars. It was observed that spiral bars experienced lower moment strength at ultimate capacity as compared to traditional deformed bar owing to their lower T/Y ratios. Spiral bars with an effective area of 0.113 in. 2 experienced higher deformation capacity than equivalent conventional deformed bar, therefore they can be used in gravity slab systems. Splice test results of 0.068 in.2 spiral bars indicated their good bond characteristics with concrete, however, they had lower ductility which led to lower slab deformations.