PSI - Issue 47

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S. Zolfaghari et al./ Structural Integrity Procedia 00 (2019) 000–000

Shakiba Zolfaghari et al. / Procedia Structural Integrity 47 (2023) 398–407 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IGF27 chairpersons Keywords: Strengthening; FRP sheet; EBROG technique; single-lap shear test; debonding; bond strength. 1. Introduction Strengthening of reinforced concrete structures using FRP composites has gained significant popularity among professional designers in comparison with traditional methods of strengthening. To achieve a reliable, efficient and optimal strengthening, it is very important to pay attention to the performance and behavior of the FRP sheet-to concrete joint. One of the most important issues that should be considered in retrofitting using FRP sheet is to provide a suitable substrate for connecting the sheet to the desired surface. Among the common installation methods of these materials, two methods of externally-bonded reinforcement (EBR) method or surface preparation method and near surface mounted (NSM) method can be mentioned. One of the most common failure mechanisms in strengthening concrete with FRP sheets by EBR and NSM methods is early separation of the sheet from the concrete surface. The separation phenomenon occurs before obtaining the final strength of the FRP sheet; Therefore, it is considered as an undesirable phenomenon. In recent years, the grooving method in three forms of externally-bonded reinforcement on grooves (EBROG) method (Mostofinejad and Mahmoudabadi (2010)), externally-bonded reinforcement in grooves (EBRIG) method (Mostofinejad and Shameli (2013)), and externally-bonded reinforcement in/on grooves (EBRIOG) method (Saljoughian and Mostofinejad (2020)), has shown good performance in preventing premature separation and even postponing it. The steps that should be taken in EBR method are as follows: • Concrete surface repair at the joint if necessary 399 - The weak layer of the concrete surface should be removed; so that the aggregates are visible and a suitable bed is provided for connecting the composite to the concrete. The preparation of the concrete surface makes the connection stronger and postpones the debonding. - The concrete surface should be roughened using different methods such as water spraying or sand spraying to develop more adhesion. - Dust and any pollution remaining on the concrete surface should be removed. • Applying suitable resin compatible with fibers on the prepared surface • Installation of FRP on concrete surface. In EBROG method, grooves with specific dimensions and positions are created on the surface of the member and dust and pollution are removed from the concrete surface using a compressed air compressor. Then the grooves are filled with suitable resin and the connecting surface is coated with resin and the FRP sheet is installed. Hosseini and Mostofinejad (2013), Ghorbani et al. (2017), Mostofinejad et al. (2018), Moshiri et al. (2019), Moghaddas and Mostofinejad (2019), Tajmir-Riahi et al. (2019), Ghahsareh and Mostofinejad (2021), Zamani and Mostofinejad (2022), Zolfaghari et al. (2023), Moshiri et al. (2023), and Yazdani et al. (2023) studied the effect of the EBROG method on single-lap shear tests. Mostofinejad and Kashani (2013), Mostofinejad and Moghaddas (2014), Tehrani et al. (2019), and Sabzi et al. (2020) investigated the effect of grooving method on the behavior of concrete beams. Extensive studies have been conducted on the behavior of reinforced concrete columns strengthened by the EBROG method (Saljoughian and Mostofinejad (2018), NoroozOlyaee and Mostofinejad (2019), Saljoughian and Mostofinejad (2020), Razavi et al. (2021), Taherirani et al. (2022), and Saljoughian et al. (2023)). Also, the effectiveness of this method in improving the performance of reinforced concrete slabs (Torabian et al. (2020), and Moshiri et al. (2020)) and beam-to-column joints (Mostofinejad and Akhlaghi (2017), Mostofinejad and Hajrasouliha - Surface defects must be repaired with repair mortar. - Cracks should be filled by proper epoxy injection. - The possible corrosion of reinforcements should be eliminated. - Surface irregularities should be corrected with putty. • surface preparation