الفهرس 
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Abstract
Repairing and strengthening structures have grown widely in the past few decades.Many reinforced concrete elements need strengthening due to the need of increasing the service loads or repair due to overloading stress or deterioration affecting these elements. However, the strengthening of these elements is overwhelmingly made without any sustained loads. This case of strengthening is not realistic. In nature, the applied loads can only be reduced but not totally removed.Seven reinforced concrete beams with dimensions 120 x 250 x 2100 mm were experimentally tested, these beams are divided into a reference beam (A) and two groups of beams. Each group consists of three beams that were repaired with three different reinforcement ratios. The beams of group (1) were repaired under zero load, on the other hand the beams ofgroup (2) were repaired under 70% percent of service load. The purpose of these two groups is to study the difference in ultimate load, strain, and deflection of repairing beams at two conditions of loading. Results showed that the beams strengthened under sustained load were found to give a higher ductility and deflection than the beams strengthened without sustained load. Also the comparison in ultimate load showed that there was almost no difference can be mentioned. A theoretical study was made based on using the integration of the curvature method (M-ϕ diagram) to calculate the load-deflection curves for all the experimentally tested beams. Results showed that the deflections of loaded beams have higher values compared to unloaded beams particularly up to yielding zone.