Serviceability and Ductility of Partially Prestressed Concrete Beams Under Limited Cycles of Repeated Loading (original) (raw)

2019, International Journal of GEOMATE

This paper deals with the flexural strength as well as serviceability performance of partially prestressed concrete flexural members with bonded and unbonded prestressed strands under limited cycles of repeated loading. The experimental program involves testing twelve beams divided into two groups. The first group, which exposed to monotonic static loading, consists of six beams, three with pretension-bonded strands and the other three with post-tensioned unbonded strands. In all the six specimens seven-wire strands, with 12.7 mm diameter and Grade 270, were used as internal prestressed steel. In addition, different amount of deformed reinforcing steel were used as bonded nonprestressed reinforcement. The second group consists of six beams, identical to the specimens of the first group, subjected to ten cycles of repeated loading. The range of the repeated loading was varied between a lower level and an upper level, equal to 40 and 60 percent, respectively, of the ultimate flexural capacity of the specimen. The effect of repeated loading on first cracking load, cracking behaviour, load carrying capacity, strain in nonprestressed and prestressed steel, strain in concrete and load deflection hysteresis were discussed in detail. It was observed that the limited cycles of repeated loading have a minor effect on the ultimate strength of partially prestressed concrete beams but it has a significant effect on deformability and cracking behaviour. The increase in midspan deflection was between 4.5% and 56%, while the crack width increase was between 14% and 300% for partially prestressed compression-controlled and partially prestressed tension-controlled with unbonded strands beams, respectively.