Bond slip model (NSM)
Prof Yasmeen T. Obaidat
Empirical Bond slip model
• Possible failure modes in the NSM FRP system
Typical bond-slip law
Geometry of NSM reinforcement.
Shear stress profile along the bonded length of an NSM-concrete joint associated with a
bilinear
• Seracino et al. (2007a)
This model is not based on the solution of Eq. but on a nonlinear
statistical analysis of the NSM-concrete joint results , which comprised
FRP strips that failed due to cohesive debonding within concrete
where
was defined assuming a linear increase of the joint bond
capacity with increasing the bonded length up to effective length Leff, which
was considered equal to 200 mm regardless of the prop erties of the NSMconcrete joint.
• fc: concrete compressive strength fc comprised between 30 and 65 MPa
• Lb: bonded length between 100 and 350 mm,
• df:depth of the reinforcing strip between 10 and 20 mm,
• wf: thickness of the reinforcing strip between1.2 and 2.4 mm.
•
• Seracino et al. (2007b)
• This is valid for strips applied with either the EBR or the NSM
technique that failed due to cohesive debonding within concrete
• If the adhesive thickness is higher than 1 mm, the fracture path will
occur within the adhesive.Otherwise it will occur within the concrete
• Where
The interface fractureplane aspect ratio
• Ali et al. (2008)
• for
• for
where
• Cper is the length of the fracture path, taken as the sum of the lengths
of the groove’s three sides
•.
• for specimens with properties in the ranges
• Zhang et al. (2014)
• for
• Zhang, S. S. et al. (2017). Effect of groove spacing on bond strength of near-
surface mounted (NSM) bonded joints with multiple
FRP strips. Construc on and Building Materials.2017
Effect of groove spacing
• The bond strength model for bonded joints with multiple evenlyspaced FRP strips can be expressed as
hg is the groove height
• Zhang, S. S. 2018.
• Effect of concrete edge distance
• a coefficient βe was calibrated using the numerical model
hg is the groove height
• Willis et al.
• for application to NSM-masonry systems