Fiber Reinforced Polymer Strengthening of Structures by Near-Surface Mounting Method

Abstract

This paper provides a critical review of recent studies on strengthening of reinforced concrete and unreinforced masonry (URM) structures by fiber reinforced polymers (FRP) through near-surface mounting (NSM) method. The use of NSM-FRP has been on the rise, mainly due to composite materials' high strength and stiffness, non-corrosive nature and ease of installation. Experimental investigations presented in this review have confirmed the benefits associated with NSM-FRP for flexural and shear strengthening of RC and URM structures. The use of prestressing and anchorage systems to further improve NSM-FRP strain utilization and changes in failure modes has also been presented. Bond behavior of NSM-FRP-concrete or masonry interface, which is a key factor in increasing the load capacity of RC and URM structures has been briefly explored. Presented studies related to the effect of temperature on the bond performance of NSM-FRP strengthened systems with various insulations and adhesive types, show better performance than externally bonded reinforcement (EBR) FRP retrofitting. In summary, the presented literature review provides an insight into the ongoing research on the use of NSM-FRP for strengthening of structural members and the trends for future research in this area.

Arching in concrete slabs strengthened with near surface mounted fibre reinforced polymers

“…As loads are considered as midspan knife edge loads, the bending moment due to arching, M a , can be related to an equivalent knife edge load, P a , using equation (19).…”

“…Common trends in the restraint stiffness variation were also observed within test subgroups. Due to the very small movements involved; and very low strains within restraint beam reinforcement at initial stages of loading; the sensitivity of LVDTs (±0.01mm) and ERS gauges (±0.85 μm/m/⁰C); only equivalent experimental restraint stiffness values which became significant in the latter stages of loading have been illustrated in graphical output (see Figures 15,17,19,21 and 22) for these investigations. This is primarily because only the external in-plane restraint at peak load is required for predicting arching capacity and also because CMA develops only after slab cracking occurs.…”

“…However, they can also be applied to multi-storey building frame elements [13] [14]. In most cases, strengthening has been carried out using conventional adhesive application (CAA) [15][16][17], near surface mounting (NSM) [18] [ 19] or by plate fastening [20]. FRPs have relatively low weight and good corrosion resistance and their application using the NSM technique involves minimal intrusion within the structure and minimises exposure to fire, which is seen as particularly advantageous in situations involving the structural retrofit of multi-storey buildings [21].…”

Reinforcing the Structural Stability of Old Nationally Important Trees with FRP Wraps

“…This is especially true for the use of fiber-reinforced polymers (FRP) of the type used in this study, as although they are becoming popular with civil engineers and architects seeking to add strength to structures, this is a relatively new method for tree reinforcement [12][13][14]. The objective of this study was therefore to analyze the structural effects of using fiber-reinforced polymer (FRP) wraps around the trunk of a carefully preserved old and large tree of national importance that is subjected to high wind loads, taking into account the anisotropic material properties of both the wood and the FRP wrap material using finite element (FE) models specially developed for this project.…”

Experimental Study of Behaviour of Reactive Powder Concrete Strengthening by NSM-CFRP Corbels

“…AZADAH (2016) [13] the technique of near surface mounted FRP is capable to achieve higher strains than external bonded reinforcement technique (EBR), resulting in more efficiency by using FRP materials, thus improving shear and flexure capacities for structural members in addition to improving ductility. In lower steel reinforcement ratio of RC members the NSM-FRP strengthening is more efficient.…”