Title:
Shear Strengthening of RC Beams Using Partial‑Length Near‑Surface Mounted (PLNSM) CFRP Strips
Author(s):
Senghong Khol, Soo‑Yeon Seo , Hai Van Tran and Muhammad Usman Hanif
Publication:
IJCSM
Volume:
19
Issue:
Appears on pages(s):
Keywords:
Shear strengthening, Near-surface-mounted (NSM), Partial length NSM (PLNSM), T-beams, Hybrid approach, RC beams
DOI:
Date:
3/31/2025
Abstract:
Shear strengthening of reinforced concrete beams using near-surface mounting (NSM) method with fiber-reinforced
polymer (FRP) strips is more effective because of improved bond strength, better fire resistance and high
maintainability. However, the surface preparation for NSM method is a difficult process where the beam–slab corner
is not accessible by the rotary blade of the groove-making equipment. Consequently, the application of NSM
method becomes more difficult to apply. Therefore, in this study, the effect of reducing in NSM length on the shear
strength has been investigated by reinforcing only a part of the height, not the entire web of beam, referred to as the
partial-length NSM method (PLNSM). Half scaled five RC T-beams were made and tested under symmetrical fourpoint
static loading system. All except one was strengthened in shear in which the effect of reduced NSM length
was balanced by inclining the partial-length NSM strips (IPLNSM). Furthermore, to mitigate the detrimental effect
of reduced lengths of NSM strips, the retrofitting was enhanced by additional externally bonded reinforcement (EBR)
method using CFRP sheets. The results showed that there was no significant negative effect of reduced NSM length
on the strength of the strengthened specimens, and by providing inclined NSM strips, significant improvement
in the strength was observed. Additionally, the hybrid approach combining the inclined partial length NSM (IPLNSM)
and EBR method showed improvement in strength and deflection capacity. Lastly, when compared with the currently
available design procedures, it was found that the available formulation can predict the design strength of PLNSM
and IPLNSM reinforcement, thus making them a viable option for retrofitting reinforced concrete beams.