The Influence of Concrete Surface Preparation when Fiber Reinforced Polymers with Different Anchoring Devices are Being Applied for Strengthening R/C Structural Members

Abstract

The aim of this study is to investigate the influence of concrete surface preparation when either steel or carbon fiber reinforced polymers (FRP) are applied for strengthening applications of R/C members. The present study also investigates the anchorage or not of the applied FRP strips on the volume of concrete. For this purpose special concrete specimens were fabricated and were used to attach CFRP or SRP strips with or without anchoring and with or without contact surface treatment. The experimental results indicate that the concrete surface preparation is important and results in an increase of the load bearing capacity when the FRP strip is not anchored. When an anchoring device is employed, the concrete surface preparation is of no significance. With a properly designed anchoring device, a significant increase in the bearing capacity was observed and the failure was that of the fracture of the FRP strips for all such specimens. The highest FRP material exploitation was achieved in the specimen that utilises the patented anchoring device together with two layers of SRP strips. Debonding of the FRP strips, or failure of the anchoring device, results as was to be expected, in relatively unsatisfactory FRP material exploitation.

Bond behaviour of Steel Reinforced Polymer strengthening systems

“…The first application of SRP in civil engineering was proposed in 2004 for the flexural strengthening of reinforced concrete beams [1]. Since then, a number of studies have been carried out to investigate the mechanical properties and durability of the steel textiles [2,3], and the shear bond performance on concrete [4][5][6][7] and masonry [8][9][10][11][12] substrates. Experimental tests on medium and large scale specimens have shown that Steel Reinforced Polymer is an effective and cost efficient solution for the strengthening of reinforced concrete (see, amongst others [13][14][15][16][17]) and masonry [18][19][20] structures.…”

Investigation of Novel Anchoring Devices for Open Hoop CFRP Strips Bonded on R/C Elements Under Monotonic and Cyclic Loading-Unloading Conditions

“…The present research aims to investigate the effectiveness of a specific FRP anchoring device (SWFX) combined with a typical FRP strip, by applying them to a number of small concrete prismatic specimens, which can house such strengthening systems with sufficient width and length. Totally 12 specimens were investigated utilizing the novel experimental setup developed on the Laboratory of Strength of Materials and Structures (LSMS) [7,16] which is presented in figure 1. The details of all specimens are presented in the following Table 1.…”

“…Apart from the good bonding an alternative way is to use appropriate anchoring devices. It was also shown [7][8][9][10][11] that utilizing mechanical anchors one can rely less on the bond which is provided to the FRP-concrete interface by the use commercially available epoxy resins.…”

Investigation of the Force Transfer Mechanisms for Open Hoop FRP Strips Bonded on R/C Beams with or without Anchoring Devices

“…In this way the premature debonding failure of the FRP strip can be avoided. Numerous researchers [18][19][20] have conducted experiments to study this debonding type of failure and to investigate means for improvement. It was shown that the desired capacity of such an R/C member strengthened with the use of FRP's can be reached more easily when this debonding type of failure of the FRP sheets is delayed.…”