Local and global bond characteristics of steel reinforcing bars: Fid-Bau Portal

Local and global bond characteristics of steel reinforcing bars

Haskett, Matthew / Oehlers, Deric John / Mohamed Ali, M.S.

AbstractThe development of an accurate local bond stress–slip $(τ – δ)$ relationship for steel reinforcing bars has been hindered for two reasons: because steel reinforcing bars are internally encased, it is difficult to strain gauge the reinforcing bar to quantify the change in strain over a given length and, therefore, to directly measure the local $τ – δ$ relationship; and because of the presence of yielding, which generally occurs before debonding and significantly influences the behaviour of the reinforcing bar. To overcome these difficulties associated with quantifying the local $τ – δ$ relationship of steel reinforcing bars, theory developed to obtain the local $τ – δ$ relationship from the global load slip $(P – Δ)$ response of FRP plated reinforced concrete structures has been modified in this research to account for short embedment lengths. Furthermore, in this paper, a link between the global load–slip $(P – Δ)$ response and the local $τ – δ$ relationship of steel reinforcing bars, that is independent of embedment length, is presented for the first time. Additionally, the new theory is used to derive the local $τ – δ$ relationship from test results and to illustrate the effect of corrosion on the local $τ – δ$ relationship which quantifies the amount of corrosion to cause bar debonding in RC beams.