Ultimate Unbonded Tendon Stress in CFRP Strengthened Post-TensionedIndeterminate I-Beams Cast with HSCs

Based on the bending experiment for two-span continuous post-tension beams with unbounded tendonsand externally applied CFRP sheets, the analysis of the stress increment of unbonded tendons ismonitored in the loading process. Since self-compacting concrete (SCC) is a suitable innovation,,understanding the implementation of this type of concrete on the ultimate unbonded tendon stress iscritical. For these aims, results of four continuous un-bonded post-tensioned I-beams in two groupswere cast and monitored by electrical strain gauges andare presented here. In the first group, the beams(UPN1-12, SUPN1-12) consisted of high strength normal concrete (HSNC), while in the second group(UPS1-12, SUPS1-12) high strength self-compacting concrete (HSSCC) were tested. The beams aremade which are compared with the theory proposed by different codes, and a preliminary modificationis given for each code equation. The results of standard error of estimate Sy/x , indicates that for twotypes of HSCs (strengthened and non-strengthened beams), the ACI 318-2011 provides betterestimates than AASHTO-2010 model, whereas this model provides better estimates as compared toBS8110-97.Comparison of increase in experimental ultimate tendon stress of beams indicates that theincrease in tendon stress at ultimate state in strengthened beams is lower than that in non-strengthenedbeams cast with HSCs.