SERVICEABILITY AND DUCTILITY OF PARTIALLY PRESTRESSED CONCRETE BEAMS UNDER LIMITED CYCLES OF REPEATED LOADING

Abstract

This paper involves the results of the study undertaken on the partially prestressed concrete beams with bonded prestressing steel subjected to limited cycles of repeated loading. The flexural behavior of partially prestressed concrete beams has been investigated through an experimental program involving testing six full-scale simply supported beams with a clear span of (3000) mm. The goal of this study was to investigate the effect of limited repeated loading cycles on strength and serviceability (cracking and deformability) of partially prestressed concrete beams. Accordingly, these beams were divided into two identical sets. The first set consisted of three beams, one of tension-controlled, the second of transitioncontrolled, and the last one is compression-controlled. These beams are tested under static loading and considered as controlled beams. They were subjected to four-point bending by using two symmetrical concentrated static loads up to destruction. The loads were applied at the middle third of the clear span length. The second set consisted of exactly the same three beams as in set one but they were subjected to ten cycles of the repeated load. The range of repeated load was between “0.4 to 0.6” of ultimate load produced from the static test. After the ten cycles, the load was released and then the beams were subjected to monotonic static test until failure. Readings were made for strains in nonprestressed and prestressed steel, midspan deflections, crack widths and crack spacing at different loading increments. Findings show that partially prestressed compression-controlled beams were less sensitive to the repeated loading.