Experimental investigation on RC beams with prestressed NSM system

Recently, rehabilitation of concrete structures with fiber reinforced polymer (FRP) has grown to be an extensively used system in most parts of the world. The main aim for this is that it is possible to obtain a suitable strengthening effect with a relatively small work effort. Nevertheless, when strengthening a structure with FRP, it is often not possible to make full use of the FRP due to de-bonding ruptures. This disadvantage of early de-bonding can be overcome by using a near surface mounted (NSM) strengthening system. In addition, prestressing can be more effectively introduced in the NSM strengthening system than in another strengthening method. The effectiveness of strengthening reinforced concrete (RC) beams with prestressed NSM carbon fiber reinforced polymer (CFRP) systems was investigated. Three RC beams (600 mm deep by 400 mm wide by 6400 mm long) were tested under four-point loading test. One beam was kept un-strengthened as a control beam. Another was strengthened with a pre-tension NSM CFRP bar. The other was strengthened with post-tension NSM CFRP bar. The test results showed that strengthening with prestressed NSM beam enhanced the flexural behavoir of the beam compared to that of the control beam. The test results indicated that the prestressed NSM beams more effectively improved the cracking, yielding and ultimate loads than the control beam. The post-tension NSM systems was determined that enhances the beam performance under concrete cracking, steel yielding and ultimate loads.