MOMENT REDISTRIBUTION AND DUCTILITY (THEORETICAL AND EXPERIMENTAL) OF CONTINUOUS UNBOUNDED POST-TENSIONED I-BEAMS CONSISTING HSSCC

The main aim of this research is to investigate, mode of failure, determination of moment redistribution, and ductility using High Strength Self-Compacting Concrete (HSSCC) in indeterminate post-tensioned unbonded continuous (full scale of 9m span) members. To do so, first, in the fresh phase, such concrete was designed and cast successfully based on the international criteria. Then the application of such concrete consisting of f′c=95
MPa was investigated on the design and constructed continuous beam, having two unbonded post-tensioned cables of variable eccentricity. The monitored results are compared and evaluated by six different Standards results. The theoretical higher and lower percentages (25 and 15) moment redistribution were achieved using CEB-FIP and EC2, DIN, respectively. The the of experimental moment redistribution value of %24.1, is almost the same as theoretical higher value while it is %61 lesser than the lower theoretical value. However, the ACI 318 and BS 8110, predict %15 of moment redistribution for such members.It was found that the bonded steel reinforcement in unbonded post-tensioned beam casted with HSSCC plays an important role in the ultimate flexural strength, especially while considering the crack distribution and ductility. The tensile bonded steels (at negative and positive moment regions) reached their yield stress; by increasing the load, a large deflection occurs and, finally, at the ultimate load, the strands were broken at a stress of 1367 MPa
with huge noise. At beam failure, different types of cracks (flexural and flexural-shear cracks) occurred and the beam experienced a deflection ductility index of 14, which is more than the suggested value of 3.5 for RC members