Structural Engineering

Permanent URI for this collection

http://etd.aau.edu.et/handle/12345678/138

Browse

Browsing Structural Engineering by Author "Abenezer, Negussie"

Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    Enhancement of the Flexural Behavior of CFRP Strengthened RC Beams in Medium and Low Grade Concrete
    (2018-10-24) Abenezer, Negussie; Girma, Zerayohannes (PhD)
    Carbon Fiber Reinforced Polymer (CFRP) has been proved to enhance the flexural strength of Reinforced Concrete (RC) beams and there is a wide range of application all over the world. As new strengthening technique Externally Bonded Reinforcement (EBR) FRP has developed and penetrated the market so quickly, however, its effectiveness on low strength concrete is questionable and there is also a minimum concrete compressive strength limit on some deign codes like ACI-2.R-08. The rationale behind this limit is not discussed in the code and measure that could be taken to improve FRP strengthening techniques at lower concrete grades is not yet known. This research assesses different flexural strengthening techniques on medium and low concrete grades including the minimum limit recommended by ACI. A new CFRP anchorage technique is also proposed and its performance is compared with other prevailing application techniques. To do so, RC beams of medium and low concrete strength are casted in the laboratory and tested with a three point loading then the result is used to validate the concrete and steel material model on Abaqus non-linear finite element software. Other experimental results are also used to validate EBR CFRP and end wrapped CFRP strengthened beam models after different interaction models have been tried on the software. With the best fitting models validated to represent CFRP strengthened beams, additional simulation works are done together with section analysis and other analytic manual calculations. With a one layer 1.4 mm thick SIKA Carbodur E-1014 CFRP Laminate, remarkable strength and stiffness increment is observed in all concrete grades and application techniques. However, beams with lower concrete compressive strength close to ACI limit are found prone to FRP end delamination at their ultimate capacity. More study was done on the delamination of these low strength beams and the new anchorage technique delayed the delamination of FRP and increased the ultimate load capacity. The other very important benefit gained from application of the new anchorage is that it dislocated the delamination initiation from the end of the FRP to the middle of the beam which is less brittle in nature compared to the one that initiates at the end of the FRP.