| Structures built before the implementation of modern seismic codes often exhibit
deficiencies in reinforcement and aggregate interlocking capacity, particularly at their connections.
These deficiencies critically impair their ability to transfer shear forces, compromising seismic
performance, strength, and stiffness. This research aims to investigate the application of
bidirectional +/-45-degree fiber reinforced polymer (FRP) to improve shear transfer capacity
across slab-to-wall concrete connections. Shear transfer capacities of eighteen non-ductile slab-towall connection specimens were assessed in this experimental investigation. Out of the six
benchmark specimens, three had roughened surfaces, while the remaining three featured smooth
cold joints. The twelve retrofitted specimens also featured smooth cold joint connections with bond
breakers at the interface and retrofitted with externally bonded glass FRP (GFRP) and carbon FRP
(CFRP), incorporating carbon anchors. The retrofitted specimen, SP17, incorporating four layers
of glass laminate with dowel and multi-splayed carbon anchors, achieved an average shear transfer
capacity of 76.16 kips. This represents an 850% increase compared to the smooth cold joint
benchmark (SP6) and a 70% improvement over the roughened surface cold joint benchmark (SP2).
The use of multiaxial and dowel anchors significantly minimized FRP debonding, leading to
enhanced shear transfer performance. Provision of GFRP laminates in conjunction with carbon
anchors at the connection provides an effective retrofitting solution to existing non-ductile concrete
members connection, increasing overall seismic performance of the structures.
Keywords: Bidirectional FRP, Carbon Anchor, Shear transfer, Seismic Retrofit, Cold-joint
concrete interfaces |