Effective length and area of bolted steel plates attached externally to strengthen reinforced concrete beams

Abstract

In this research an investigation has been done on eight reinforced concrete beams. Each beam was strengthened by bolted steel plates attached to their bottom side, of which length and thickness ratio varied, except one beam which has been tested without steel plate as controlling test. Two limits have been introduced upon the maximum plate area used and its minimum length. The first limit is to insure a ductile tension failure, and the latter is to prevent loss of interaction between the two components. Bolts with head were used to provide suitable connection through the specimens of concrete beams and the steel plates through predrilled holes in the steel plates. All beams have similar dimensions and tested simply supported over an effective length of 1600 mm and loaded with central load. Test results show that the plated beam gain an increase in strength over that of unplated beam of about 145%. Also, beams with relatively thin plates, the plate length has little effect upon the ultimate strength, however, for beams with thicker plates the results show a decrease in strength of about 16%.