الفهرس 
NECESSITY OF STRENGTHENING REINFORCED CONCRETE SLABS
MECHANICAL PROPERTIES OF STEEL TENDONSOnly 14 pages are availabe for public view
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Abstract
Strengthening and/or repair of Reinforced Concrete (RC) structures by use of external prestressing have now been used for some time. The main advantages using this technique are; higher utilization of small sectional areas, ease in inspection and replacement of the tendons and low friction losses. The application of external prestressing to deteriorated, overloaded or aged existing structures/members using unbonded tendons is proving to be a very effective mean of strengthening structural elements or systems and have been shown to not only increase the life expectancy of the member or system, but to increase the flexural strength considerably, resulting in reduced deflection and crack widths. Generally, the efficiency of external prestressing, as a strengthening system, is affected by several factors and one of the main factors is concrete strength. However, during the rehabilitation of old reinforced concrete structures the strength of concrete of existing elements in need of repair cannot be altered. So, in case of low concrete strength the increase of the flexural strength that external prstressing can provide is limited by the maximum allowable compressive stress in the compressed part of the slab. This research aimed to develop and evaluate an innovative strengthening technique for low strength concrete slabs based on Engineered Cementitious Composites (ECCs) applied on compression side of slab prior to application of external prestressing tendons. The role of the proposed ECC layer is to avoid early concrete crushing in compression side, and consequently increase the efficiency of external prestressing.