Strengthening behavior of reinforced concrete T-Beams using external per-stressed tendons

The Experimental investigations of strengthening reinforced concrete Tbeams by external prestressed tendons are presented. The tested beams are partially strengthening span instead of strengthening whole span technique as convention. The test variable is chosen to study the effects of tendons depth levels relative to beam top fiber expressed as depth ratio (eccentricity) which is equal to depth of the strand to height of the section. Therefore, this study has been conducted to show the ability of using partial span strengthening and the effectiveness of increasing depth ratio of the external strands. Four identical reinforced concrete T-beams were tested up to failure. One of these beams (without strengthening) was used as a reference or control beam. While, the other three beams were partially strengthened (only 83% of the effective length) with two tendons. Tested beams were strengthening by fixed tendons in variable level and configuration by jacking at a constant stress equal to 600 MPa. All beams were tested up to failure by applying two concentrated loads at the third points. The test results show the ability of using partially strengthening technique to improve and enhance an existing beam. The important parameters that affect the behavior, such as failure mode, crack pattern, strain profile, and deflection at mid span are evaluated and discussed. Generally, test results shows that the deflection under service load decreases and the load capacity of the strengthened beams increase with increasing in the depth ratio of external strands.