نوع مقاله : یادداشت فنی
دانشکدهی فنی و مهندسی، دانشگاه شهید باهنر کرمان
عنوان مقاله [English]
To achieve acceptance for the use of high strength self compacting concrete, HSSCC, in pre and post tensioned elements, this study was conducted. Investigation into the mechanical property effects of the fairly new concrete generation of HSSCC was performed by the first author and, for the designed HSSCC mix, the fresh properties (Slump Flow, L-box, V-funnel and J-ring tests), as well as hardened properties, such as compressive and flexural strength, modulus of elasticity, shrinkage and swelling, were measured at different ages and reported elsewhere. However, it was concluded that while producing HSSCC, it is possible to reduce the amount of shrinkage and swelling by 69% and 30%, respectively, when compared with ordinary self compacting concrete, SCC. In other words, by applying high strength SCC in prestressed elements, it is possible to reduce the total amount of prestress losses. Therefore, as a general conclusion, current knowledge of HSSCC shows that there are definite advantages, both technical and economical, in using a higher concrete strength in prestressed concrete structures. Greater strength per unit cost and per unit weight, increased modules of elasticity and reduced shrinkage and creep are some of these advantages. Theoretical and experimental research is required to understand the effects of concrete strength on unbonded post tensioned continuous slabs consisting of SCC. As no research work is available on the structural behavior of HSSCC used on post tensioned continuous bridge decks, a research program was conducted at Shahid Bahonar University of Kerman under the first author. For this purpose, first, a review is made on the concept of moment redistribution from the point of view of different standards, based on normal (vibrated) concrete. The relations for normal concrete are evaluated by casting and experimentally load testing two unbounded continuous post tension HSSCC slabs, having 7.5m length, 1.0m width and 0.2m height. The theoretical and experimental results indicated that it is safe to make use of available standards on vibrating concrete for moment redistribution calculations of tested slabs consisting of this type of non vibrating concrete. With the obtained range of results, it was found that HSSCC will consolidate exceptionally well under its own weight, even for elements containing high amounts of reinforcement.