Prevention of Peeling Failure in Plated Beams

Abstract

Peeling failure is one of the main drawbacks of reinforced concrete (RC) members strengthened by externally bonded plates. Two different techniques are suggested to prevent peeling failure at the ends of steel plates glued to the soffits of RC beams. In the first technique, concrete cover is replaced by grout to enhance the resistance of substrate to crack initiation and propagation. In the second technique, permanent compressive forces at the ends of bonded plate are applied using different plate end anchorage systems, i.e. end anchorage by bolts or by clamps. Furthermore, two different sizes of side plates, with and without end anchorage, are glued to the plated beam to delay or prevent the peeling failure. An analytical model is suggested to predict the load-deflection behavior of beams strengthened by bonded steel plates at the bottom and sides of the beams. The results of 4PB tests indicate that conventional plated beam (PB) experience reduction in ductility and limited enhancement in ultimate load, which increased only by 22% compared to unplated beams due to the occurrence of peeling failure. Peeling failure of plated beams can be prevented through the use of either a concrete cover replacement technique or bolted anchorage systems. Anchorage of a side plated beam increased the ultimate load by 264% compared to an unplated beam and 217% compared to PB.

Structural Behavior of RC Beams Containing a Pre- Diagonal Tension Crack

“…By increasing the applied load, the coalesced crack will propagate till failure point, as shown in Fig.6. A similar behavior was observed by (Sallam et al 2004;Yehia and Wahab 2007) for pre-cracked Reinforced concrete beams under mode I, at which, the pre-crack propagated at a load equal to that of smooth specimens at the same crack length.…”

“…Fracture mechanics concepts were successfully applied on propagating cracks under mode I (opening mode). Sallam et al (2004) proved that, the behavior of pre-cracked specimen is identical to that of smooth specimen when the generated crack in the smooth specimen reaches an equal length as that of the pre-cracked one. The behavior of both specimens is different at the stage before generating the first crack till it reaches the pre crack length.…”

Flexural behavior of RC beams strengthened by NSM GFRP Bars having different end conditions

“…Hybrid bonded FRP technique [26] and U-anchor system [27] are suggested to prevent such type of failure. Sallam et al [2] found that cover separation or debonding failure in EB system can be prevented by concrete cover replacement technique.…”

“…Although the use of EB technique increases the load carrying capacity of the RC strengthened members, the NSM FRP strengthening technique offers many advantages over EB. These advantages include increasing bond capacity due to larger bonded surface area and make a protection against external damage results from external impacts, since the bar is embedded in the concrete cover [1,2]. Although the researches indicated that the EB and NSM techniques are effective techniques for increasing both flexural and shear capacity of structural members [3][4][5][6], the failure due to debonding of FRP reinforcement is still the most common failure mode [7][8][9][10].…”

Strengthening of RC T-beams with perforated steel plates

“…Raoof et al (2000) were able to establish that the premature plate peeling failure can be prevented by increasing the concrete strength, the ratio of the beam width to the plate width, the diameters of the internal tension rebars, and the number of layers of tension reinforcement. The experiments conducted by Sallam et al (2004) indicated that the ductility of a plated RC beam can be improved by replacing the cover concrete in the plate curtailment regions with a grout of higher strength or applying initial compressive stresses to the plate by pressing it against the beam with the help of clamps or bolts. Arslan et al (2008) experimentally showed that the contribution of collar anchorage of the plate ends to ductility stems from the resistance provided by the collars to crack propagation at the plate curtailment locations.…”