PSI - Issue 64

Annalisa Napoli et al. / Procedia Structural Integrity 64 (2024) 975–982 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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2. Overview of the experimental research Despite the external steel plating of RC members being rather outdated as a strengthening technique, the experimental studies investigating the flexural behavior of RC beams strengthened with steel plates are not numerous. Furthermore, since most researches were carried out about the ‘80s and ‘90s , concerns are also related to the difficulty in collecting bending tests results of RC plated beams from the scientific papers; in some cases, the lack of relevant data related to the geometry of specimens or to mechanical properties of either internal or external steel reinforcement make the related tests and results not useful for theoretical studies or design considerations. The pie charts in Figure 1 provide a general overview of the experimental database compiled from the literature, which includes all the specimens for which the main information is available. In detail, as shown in Figure 1a, the collected test members are 73 (all simply supported beams) which were extracted from 13 scientific papers, of which 57 were externally strengthened in tension by using externally bonded (EB) steel plates (Adhikary and Mutsuyoshi 2002; Ajeel et al. 2011; Aykac et al. 2013; Jumaat et al. 2007; Jumaat and Alam 2008; Jones et al. 1982; Sallam et al. 2004; Jansze 1997; Ozbek et al. 2016; Täljsten 1994; Thamrin, R., 2017; Salman 2015) and the remaining ones (16) were reinforced by means of mechanically fastened (MF) steel plates (Roberts and Haji-Kazemit 1989); in the latter case, the mechanical fastening was not combined with the use of epoxy for bonding the external reinforcement to the concrete substrate. In 25 out of 57 beams strengthened with the EB steel reinforcement, mechanical anchors (bolts, clamps or L-shape elements) were added to improve the connection of the external reinforcement to the RC member with the aim to prevent or delay the premature failure of the strengthened member by plate debonding (Adhikary and Mutsuyoshi 2002; Aykac et al. 2013; Jumaat et al. 2007; Jumaat and Alam 2008; Sallam et al. 2004; Salman 2015); in some cases, the anchors were arranged at the beam ends only, in others they were distributed along the beams length.

Bending test configuration

EB plate w/ anchors: #25 specimens

General Database: #73 specimens

end anchors distributed anchors end clamps L-shape anchors #16 (22%) MF plate

EB plate w/o anchors EB plate w/ anchors MF plate

Four-poin Three-poin

#2 (8%)

#2 (8%)

#16 (22%)

#32 (44%)

#2 (8%)

#4 (5%)

#53 (73%)

EB plate

#19 (76%)

EB plate

#25 (34%)

EB plate w/ anchors: #25 specimens

Bending test configuration

3 specimens

end anchors distributed anchors end clamps L-shape anchors 16 (22%)

EB plate w/o anchors EB plate w/ anchors MF plate

Four-point bending test Three-point bending test

MF plate

#2 (8%)

#2 (8%)

c

b

a

#32 (44%)

#2 (8%)

4 (5%)

Fig. 1. RC beams externally strengthened with steel plates: (a) general database; (b) steel plated externally bonded to concrete in presence of anchors; (c) bending test configuration. 53 (73%)

EB plate

#19 (76%)

EB plate

The pie chart in Figure 1b shows the distribution of the 25 beams per anchors type, while Figure 2 schematically illustrates the strengthening layouts adopted in the case beams strengthened with MF or EB steel plates, the latter equipped or not with steel anchors. Concerning the bending test configuration, all the beams strengthened with MF plates were tested in three-point bending with a shear span length (L s ) normalized to the beam clear length (L c ) constantly equal to 0.5. In the case of EB plates, 53 out of 57 specimens were tested in four-point bending, with L s /L c ranging between 0.32 and 0.5; 0.5 was also the ratio adopted for the remaining specimens tested in three-point bending.