Bursting and Spalling in Pretensioned U-Beams - Ferguson ...

Grade 60 rebar yielded at 65 ksi and failed at 110 ksi. Deformed wire did notshow a yield plateau, but using the two-tangent method, yield strength was determined tobe 85 ksi. Though deformed wire yielded at a higher stress, it failed at a lower stress,95 ksi. The failure modes of the two bar types were different (Figure 3.13). The Grade 60bar failed with a cup-and-cone shape after substantial necking and a gradual loss ofcapacity. The deformed wire failed in a brittle manner.The measured elastic modulus was similar to the book value, 29,000 ksi.Reinforcing-bar tension test results are reported in Appendix D.ductilefailurebrittlefailureFigure 3.13 Failure modes for Grade 60 rebar (left) & deformed wire (right)3.4.2 Prestressing-Strand Mechanical TestingStrand testing focused on elastic-modulus testing. During stressing and release ofbeam specimens, strand behavior was to be examined through use of linearpotentiometers and strain gages. The two sets of instruments measure differentdeformations: the linear potentiometers, the linear deformations; and the strain gages, the114