Abstract
Carbon-fiber-reinforced polymer (CFRP) grid and engineered cementitious composite (ECC) were combined in this study to strengthen concrete columns. The influences of the number of layers, the overlap length of CFRP grids, and the eccentricity on the bearing capacity and rigidity of reinforced concrete columns were determined. The results show that the principal failure of the reinforced column was debonding of external ECC from FRP grids at the compressive area, edges, or sides. Significant enhancement in the ultimate bearing capacity and rigidity of eccentrically loaded columns was observed after they were externally reinforced by CFRP grids and ECC; such enhancement increased with the number of reinforced layers. Eccentricity made little difference to the enhancement rate of bearing capacity when the number of reinforced layers was the same. At different eccentricities, the composite layers at the tensile area and the compressive area had different contributions to the bearing capacity. An effective bond and efficient stress transfer could be ensured as long as the overlap length between CFRP grids reached 120 mm.
Highlights
Fiber-reinforced plastic (FRP) has been widely used to strengthen concrete structures due to its numerous advantages, such as light weight, high strength, corrosion resistance, and durability. e most common strengthening method is external bonding of FRP sheets or plates with epoxy adhesive on the concrete members; there are still some issues to be addressed, such as aging and poor durability of the adhesive [1]
(2) Since all the columns failed as concrete crushing at the compressive area, the compressive strength of concrete is critical to the capacity of an reinforced concrete (RC) column. e externally coated FRP grid-engineered cementitious composite (ECC) composite layer can provide lateral confinement to the concrete at the compressive area
The maximum tensile strain at the tensile area reached 5881 με when the column subjected to large eccentric compression reached its ultimate strength. e composite layer at the tensile area showed a high utilization ratio; the compressive area was lower, and the lateral confinement provided by the composite layer at the compressive area contributed less to the enhancement of bearing capacity. us it can be seen that the tension provided by the FRP grid-ECC composite layer at the tensile area and the lateral confinement by the composite layer at the compressive area made different degrees of contribution to the enhancement of column bearing capacity at different eccentricities, their overall contribution is roughly the same
Summary
Fiber-reinforced plastic (FRP) has been widely used to strengthen concrete structures due to its numerous advantages, such as light weight, high strength, corrosion resistance, and durability. e most common strengthening method is external bonding of FRP sheets or plates with epoxy adhesive on the concrete members; there are still some issues to be addressed, such as aging and poor durability of the adhesive [1]. Fiber-reinforced plastic (FRP) has been widely used to strengthen concrete structures due to its numerous advantages, such as light weight, high strength, corrosion resistance, and durability. FRP debonding is the primary cause of failure of concrete structures strengthened by this method. A variety of FRCM strengthening methods have been developed, including textile reinforced concrete/mortar (TRC/TRM) [6]. Brittle fracture of cement mortar will occur prior to the failure of FRP grids due to its high brittleness. To increase both the reinforcement efficiency and service life of the structure, an appropriate method should be developed to enable coworking between the cementitious material and FRP grids
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