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plating allow a greater cross-sectional area of plate to be used;
(ii) in side plating, plates are placed away from the tension rein-
forcing bar stress concentrations; (iii) side plating may provide a
more ductile section when the plate is extended transversely into
the compression zone; and (iv) side plating can increase the shear
capacity.
This paper presents results of an experimental and analytical
investigation into the effectiveness of FRP wraps in strengthening
of the joints for relocation of plastic hinge away from the joint core
toward the beam (RETROFIT) and for REPAIR of a moderately dam-
aged RC joints (using web-bonded FRP in the beam region) in an
ordinary moment resisting frame (OMRF) [10]. The proposed
method is to stick carbon FRP sheets of specific lengths to the sides
of the beams of a reinforced concrete joint (i.e. web-bonded FRP).
Authors of the current paper did not find any past studies on web-bonded FRP for beams in the published literature specifically
tailored towards joint rehabilitation. The performance of this
method has been investigated by the authors and is presented in
the following. Other aspects of the investigation can be found in
papers published by the authors, Mahini et al. [11], Mahini [10],
and Mahini and Ronagh [12,13]. The method can be used just as
effectively for the repair of earthquake damaged RC exterior joints
[14]. This work has been cited by Smith and Shrestha [8]. Research
in the area of side plating is extremely limited. To the best of the
authors’ knowledge, no tests have been undertaken on using exter-
nally bonded FRP to relocate the plastic hinge further along the
beam away from the column face. Attempts of a different nature,
however, have been made in the past to develop methods of relo-
cating the hinges away from the column face. For example, Abdel-
Fattah and Wight [15], Joh et al. [16], Paulay and Priestley [1] and
Chutarat and Aboutaha [2] used different reinforcement details in
the beam region adjacent to the column.Most of these methods in-
volve detailing of reinforcing bars, which can only be utilised in
new constructions. The method investigated in this paper is usable
in both new and already constructed (or even damaged) frames.
2. Experiments on web-bonded FRP applied to the beam end in
a joint
Fig. 1 contains the schematic view of a subassembly under load
in the testing rig. This isolated subassembly represents an external
joint in a scaled-down reinforced concrete building. specimens’
geometry and FRP configuration are shown in Table 1. Mahini
[10] performed tests on these subassemblies using the testing rig
shown in Fig. 2. Test specimens were seven 1:2.2 scale models of
the prototype. The prototype structure was a typical eight-story
residential RC building, designed as an OMRF, according to the aus-
tralian concrete code AS3600 [17] with details similar to non-duc-
tile RC frames designed to ACI-318 [18]. A scaled-down frame was
proportioned and detailed according to the similitude require-
ments of the Buckingham theorem [19]. The scaled-down joints
were extended to the column mid-height and beam mid-span, cor-
responding to the inflection points of the bending moment dia-
gram under lateral loads. All joints consisted of 180 mm wide
and 230 mm deep beams with 220 mm 180 mm columns. Rein-
forcement consisted of R6.5 (/ = 6.5 mm) ties of fy equal to
382 MPa, N12 (/ = 12 mm) main bars of fy equal to 500 MPa, and
yield strain equal to 0.0025 mm/mm. carbon fibre reinforced
plastic (CFRP) sheets that were used in all experiments were uni-directional with an ultimate stress of ffr = 3900 MPa, ultimate
strain of 0.0155 mm/mm and a constant modulus of 240 GPa.