PSI - Issue 64

Sadeq Mo. Annooz et al. / Procedia Structural Integrity 64 (2024) 1565–1572 Annooz, Williams, and Myers / Structural Integrity Procedia 00 (2024) 000–000

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Figure 4. Failure mode of mild steel bond specimens.

Figure 5. Failure mode of BFRP bond specimens.

The test results were normalized because of the difference between the design and the actual compressive strength. (ACI Committee 318. 2011) and (AASHTO 2007) use the square root of the design over the actual compressive strength while (ACI Committee 408, 2003) uses the fourth root. Both approaches were considered.;

P d l

(1)







b b

where P is the tensile load, d b is the rebar diameter, and l b is the embedment length. The relationship between the bond stress defined by Eq. (1) and the slip between the rebar and the concrete is used to analyse the bond behaviour (Baena et al. 2009). The reinforcing surface also plays an important role in the bond strength. If greater frictional resistance is developed between the rebar and the concrete, bond strength will increase. Similarly, if the bar surface treatment allows for mechanical bearing, bond strength can be improved further. ACI 440.1R-15 presents Eq. 2 for developable bar stress. �� � �� � � � � 13.6 � � � � � � � � � � � � � 340 �� �� (ACI 440.1R-15 Eq. 10.1c) (2) ACI 440.1R-15 states that embedment lengths shorter than 20d b are not recommended and that additional work needs to be performed to determine the effect of the chosen factor of safety for bond on the flexural reliability of the specimen . When applying Eq. 2 for design purposes, ACI 440.1R-15 states it should be assumed that the maximum achievable bar stress varies linearly from 0 to the value produced by Eq. 2 (ACI 440.1R-15 Eq. 10.1c) along the first 20d b of the bar embedment . Based on published durability bond related work, conditioning of bond specimens due to environment such as high temperature, alkaline environment, sustained stress, moisture, etc. have been shown to reduce bond performance.