SRP sheet strengthening of reinforced concrete beams subjected to fatigue loads.

摘要

The fatigue behaviour of reinforced concrete beams strengthened with advanced composites such as carbon, glass and aramid fibre reinforced polymer (FRP) sheets have been tested and studied during the past two decades. Steel reinforced polymer (SRP) sheets are similar to FRP sheets, however instead of advanced composite fibres in a polymer matrix, SRP is comprised of high-strength brass-coated steel wires in an epoxy matrix. To date, there has been very limited literature published detailing the fatigue testing of SRP strengthened reinforced concrete beams. Therefore, a study of the behaviour of reinforced concrete beams externally strengthened with SRP sheets and subjected to fatigue loads was undertaken. Six 3 m long reinforced concrete beams were tested to failure under cyclic loading. Three of these beams were unstrengthened and acted as control beams, while the remaining three were externally strengthened with longitudinal SRP sheets and transverse U-wraps. Three different load ranges were used to produce a stress-life curve, with one unstrengthened and one strengthened beam tested at each range. Both the unstrengthened and strengthened specimens failed due to the rupture of the tensile reinforcing steel. It was found that the application of SRP was able to decrease the stresses applied to the reinforcing steel and limit the crack widths, thus extending the fatigue life of the strengthened specimens. Fatigue life was reasonably predicted using a fatigue model based upon a strain-life approach. Neither the SRP material nor the bond between the SRP and the reinforced concrete substrate failed prior to rupture of the reinforcing bars. It was concluded that the SRP material could be used effectively for external strengthening in a cyclically loaded environment and could also be effective in extending the fatigue life of reinforced concrete beams.