Anchorage Effect on Flexural Fiber Reinforced Polymer (FRP) Laminate Strengthening of Lightweight Concrete Beams

Abstract

Lightweight (LW) concrete is finding increasing use primarily to decrease the dead load, reinforcements needed and member sizes. The beneficial effect of flexural fiber reinforced polymer (FRP) laminates in enhancing the capacity of normal-weight concrete has been well-demonstrated. However, such application on LW has not been explored in depth, especially with confining anchorage systems that can prevent premature debonding of the flexural laminates. This study investigated the effect of utilizing mechanical anchorage and FRP U-wrap anchorage on the performance of LW concrete beams. The carbon FRP laminate enhanced the flexural capacity of all strengthened beams by up to 12%. The CFRP U-wrap was found to be more effective than the mechanical anchorage in delaying the debonding failure of the flexural laminate and increasing its tensile strain by as much as 81%. However, the mechanical anchorage was more effective in increasing the elastic stiffness of the beams. Strengthened beams are likely to have increased durability due to the decreased crack width, length and spacing. The demonstrated failure modes of cover delamination and U-wrap debonding contradicted the theoretical failure mode from the American Concrete Institute (ACI) guidelines. Such guidelines do not currently include the contribution of FRP anchorage systems for concrete structures.

Structural Behaviour of Polystyrene Foam Lightweight Concrete Beams Strengthened with FRP Laminates

“…Results and failure modes Page 3 of 20 Montaser et al Int J Concr Struct Mater (2022) 16:59 of control and conditioned specimens showed that degradation of CFRP-strengthened beams was controlled by the conditioned concrete tensile strength and bond cohesive energy in the epoxy and polyurethane systems, respectively. Aljaafreh (Aljaafreh, 2016) tested eight LWC beams strengthened using CFRP. It was found that the LWC beams strengthened with the CFRP layer exhibited an appreciable increment in flexural strength compared to the control beam.…”