The strengthening and deformation behaviour of reinforced concrete beams upgraded using prestressed composite plates

Abstract

A B S T R A C T R I~ S U M I~Externally bonded steel plates have been used worldwide for over twenty years to strengthen concrete members, but the disadvantages include the transportation and installation of heavy plates and steel corrosion. Polymeric composites avoid these disadvantages and provide an equally effective method of strengthening. The advantages of composites are exploited further by prestressing them before bonding to the concrete. This paper is concerned with the response of such prestressed members to applied load.After strengthening with externally bonded carbon fibre reinforced polymer (CFRP) plates, a number of beams of 1.0 m and 4.5 m lengths were tested in four point bending. The plates were bonded without prestress and with prestress levels ranging from 25% to 50% of the plate strength. The ultimate capacities of the nonprestressed beams were significantly higher than those of the unplated members and plate prestress brought about yet further strengthening. Prestressed plates are utilised more efficiently than non-prestressed plates, since a given plate strain is associated with a lower structural deformation in a prestressed member. The internal steel rebars yielded at a higher proportion of the ultimate capacity in the prestressed beams. Prestressing lowers the position of the neutral axis so more of the concrete section is loaded in compression, making more efficient use of the concrete.

Structural strengthening of concrete beams using prestressed plates

“…It is shown that the non-prestressed member without plate end anchorage exhibited a lower post-yield stiffness than the non-prestressed beam with the bolted plate ends. This is a typical result for beams loaded with a shear span/beam depth ratio equai to or lower than 4.0 due to the stiffening influence of the plate end anchorages (Garden and Hollaway, 1997). This wouid indicate that the post-yield stiffness Df a plated beam with end anchDrage is nDt gDverned by the plate prestress and that the locus Df yield pDints, with increasing prestress, defines a straight line.…”

Bending behavior test and assessment for full-scale PC box girder reinforced by prestressed CFRP plate

“…Meanwhile, since the CFRP plate is a high tensile strength and low shear strength materials, it can be cut at the constructional site and the whole strengthening process is simple and convenient since no other constructional machine is needed. Although CFRP is an expensive material compared with traditional constructional material, its superior characters like corrosion resistance enable its application in serious environmental region and post maintenance work can be avoid after strengthening (Garden et al 1998). Thus, CFRP strengthening method is a beneficial chose for bridge engineering.…”

40-Year-old full-scale concrete bridge girder strengthened with prestressed CFRP plates anchored using gradient method

“…Furthermore, several investigations can be found in the literature where RC test beams strengthened with prestressed CFRP plates were tested and compared with unstrengthened reference beams and beams strengthened with nonprestressed CFRP plates, e.g. [3][4][5][6][7]. El-Hacha et al [8,9] studied the strengthening of precracked concrete beams using prestressed CFRP sheets under short-and long-term loading and exposure to both room and low temperatures.…”