STRENGTH AND DUCTILITY OF ULTRA HIGH PERFORMANCE FIBER REINFORCED CONCRETE BEAMS WITH EXTERNALLY CFRP SHEETS

Hamdy K. Shehab El-Din, Mohamed M. Husain, Mahmoud A. Khater

Abstract


The addition of carbon fiber reinforced polymer (CFRP) composites, which is another form of tension reinforcement, affects the ductility of UHPFRC beams strengthened with CFRP sheets. However, the flexural ductility of beams with respect to amount and and yield strength of existing ordinary steel bars has not been investigated in depth. In addition, delamination of CFRP sheets dominates the ultimate mode of failure of flexural members strengthened with CFRP sheets, which limits the ductility of strengthened members. There is a need to investigate the effect of CFRP anchorage system on the overall ductility of strengthened UHPFRC concrete beams. In this research, tests were carried out on thirty two ultra high performance fiber reinforced concrete (UHPFRC) beams to study the effects of some parameters on the flexural strength and ductility of UHPFRC beams with externally strengthening with CFRP sheets. The major parameters included in this research were the amount of internal steel reinforcement, the volume fraction of the fiber and the configurations of placement of transverse anchorages along the external longitudinal CFRP. The test results showed that externally bonding CFRP sheets on the bottom flange of UHPFRC beams led to increase load-carrying capacity but reduce flexural ductility. Also the results showed that the CFRP anchorages could significantly increase the flexural ductility, Furthermore the transverse anchorages were sufficient to eliminate debonding, and the UHPFRC beams failed when the longitudinal CFRP materials fractured, in other cases, the transverse anchorages simply delayed debonding, and the longitudinal CFRP materials debonded after the transverse anchorages fractured

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