PSI - Issue 64

Asad-ur-Rehman Khan et al. / Procedia Structural Integrity 64 (2024) 1065–1072 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

1066

2

1. Introduction Structures and their components are susceptible to losing their strengths as they go through their design life span, owing to various environmental effects, excessive loadings, and natural and man-made calamities (Rostam et al. 1992). The introduction of newer building codes and strict design code requirements may also introduce the requirement of strength upgradation (Tetta et al. 2016), along with rusting and an increase in applied loads due to usage (Brückner et al. 2006), and an increase in traffic volumes on bridges and impact loads being the other reasons for the introduction of strength upgradation (Carloni et al. 2012). Traditional shear strengthening for RC members consists of the accumulation of stirrups and an increase in the size of the given cross-section, which increases the self-weight of the flexural member being strengthened (Cheong and MacAlevey 2000). External prestressing of steel jackets is also used for this purpose (Adhikary et al. 2000; Sharif et al. 1995). The use of fibre composites has been very prominent in modern strengthening techniques for structures, especially those constructed with reinforced concrete (RC). Fibre Reinforced Polymers (FRPs) are found to be recurrently used in this regard for research (Al-Salloum et al. 2011; Carloni et al. 2012; Razaqpur et al. 2010; Triantafillou 1998) and in field applications for strength restoration/upgrade of existing structures. While FRPs have enjoyed success in strengthening RC members, they have shown some downsides as identified by researchers, including costly application, reduced fire resistance, detrimental solvents for application of FRPs, and low-grade applicability of FRP on damp seeming and at lower temperature ranges (Triantafillou et al. 2006a). Due to these reasons, cementitious binders with high workability and adequate shear and tensile strength to protect against early debonding have been used as replacements for epoxies, and the blend of fibre grids with cementitious putty is known as Textile-Reinforced Mortar (TRM). Various researchers have examined TRM with promising fallouts when carbon (Ombres et al. 2018), glass (Brückner et al. 2006), and PBO (Aljazaeri et al. 2018; Loreto et al. 2015; Sneed et al. 2015) fibres were mostly used with respect to load carrying capacity and serviceability, i.e., deflection and crack control (Brückner et al. 2006; Khan and Masood 2016b). But, basalt fibres have mainly been used for strengthening masonry construction and columns (Bournas et al. 2007; Ma and Li 2015), and the efficacy of basalt fibres has not been investigated for full scale beams, despite the fact that there has been a promising number of studies conducted on small and medium scale beams (Escrig et al. 2015; Khan and Masood 2016a; Loreto et al. 2015; Ombres 2015; Tetta et al. 2015; Tzoura et al. 2016). Fibre-Reinforced concrete (FRC) has also used basalt fibres, which have depicted value-added outcomes for enhancement in flexural and tensile attributes of reinforced concrete, with promising bond performance between matrix and basalt fibres (Ayub et al. 2014; Jiang et al. 2014). The published data reveals that U-configurated wraps have been effective with respect to member strength (Azam and Soudki 2014; Tetta et al. 2015; Triantafillou et al. 2006b; Tzoura et al. 2016). The majority of the prevailing research has emphasised specific shear span ratios (a/d), therefore not encircling the region and ranging the a/d ratios from 1 to 6. The current paper, in continuation of a study conducted by the same authors (Masood and Khan 2019), investigates the usefulness of TRM embedded with basalt fibres for the strength upgradation of flexural members in shear, flexure, and stiffness flexural strips, along with U-wrap configuration for shear, with control and corresponding TRM-strengthened beams loaded to failure. 2. Experimental Program 2.1. Reinforced Concrete Beams Six full-scale flexural members, two for each a/d ratio, were cast for this research. The clear span and the cross section used were the same as those used in the aforementioned research (Masood and Khan 2019). Out of two beams for each a/d ratio, one beam was unstrengthened and the other was strengthened with basalt fibres based TRM. Overall length of the beam between the supports was 5025 mm. The support centres on both sides were positioned 230 mm from the edge of the beams. All the beams were reinforced longitudinally with twice of ρ min as discussed in ACI 318-14 (2014) code. All six beams were provided with shear reinforcement spaced at 200 mm centres for the aforementioned a/d ratios. Beams, other than control beams, were strengthened in flexure and shear by using TRM with basalt fibres. TRM strips were used in flexure while U-shaped TRM wraps were used in shear.