Examination at a Material and Structural Level of the Fatigue Life of Beams Strengthened with Mineral or Epoxy Bonded FRPs: The State of the Art

Abstract

This paper presents a state of the art review of different material combinations and applications of mineral-based and epoxy-based bonded Fiber Reinforced Polymers (FRP), used for the strengthening of concrete structures subjected to fatigue loading. In this review, models of the fatigue life at the material and structural level are presented. This study examines the mechanical behavior of the FRP-material, surface bonding behavior and concrete beams strengthened under fatigue loading with different types of FRP-systems. The parameters that are investigated are applied load value, time dependent effects, type of strengthened structures (shear, flexural or combined) and the configuration of sheets or plates. The building codes and researchers' recommendations are also discussed. As a result of this review, the reader will obtains an overview of suitable materials and methods for strengthening structures subjected to fatigue loading by referring to the estimated fatigue life of material and strengthening structures at various applied stress levels.

Performances, challenges and opportunities in strengthening reinforced concrete structures by using FRPs – A state-of-the-art review

“…The compressive strength of FRPs is generally 20-50% of the tensile strength [40], and the risk of local layer instability and buckling failure cannot be ignored under compression [43]. FRPs with fibres in the circumferential direction, as spiral or tie reinforcement, are very effective [44,45].…”

“…Further, 70% reduced deflection and 24.7% increased first crack load were observed for a GFRP diagonally strengthened beam [80]. Researchers concluded that the tension-tension fatigue loading capacities of FRP-strengthened RC structures are unquestionable, but exhibit the worst loading capacities under tension-compression or reversed axial fatigue loading [43].…”

“…By moderating the strengthening system and fibre direction and adding steel reinforcing materials, the brittleness of FRP-strengthened RC structures can be reduced. Generally, a strong FRP-concrete bond leads to brittle failure of the whole RC structure, whereas a weak bond may cause debonding and ductile failure of FRP-strengthened structures [43]. An EB-FRP plate frequently shows debonding which is very brittle, while NSM strip strengthening can slips widely and provide higher rotational capacity [157,159].…”

Experimental Investigation of Mineral Composite Bonder over CFRP and GFRP Retrofits

“…It should provide excellent bonding properties, along with good workability, cost efficiency and most importantly compatible with most of the FRP retrofits. The investigation of mechanical behavior performed by [4] for Carbon Fiber Reinforced Composites (CFRC), plain and mineral based composite retrofitted beams to calculate their flexural behavior. As shown in Figure 1 Flexural response of plain, CFRC and CFRP retrofit Source: Mahal (2013) [5] studied FRP bond strength in a single-lap (see Figure 2) shear and flexural tests.…”