PSI - Issue 64

Eun-Rim Baek et al. / Procedia Structural Integrity 64 (2024) 1117–1124 Author name / Structural Integrity Procedia 00 (2019) 000–000

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This short paper summarizes the main findings discussed in our previously published experimental work and focuses on presenting the key experimental insights shared at the SMAR 2024 conference. 2. Experiments The structural performance of the proposed integrated retrofitting system was evaluated experimentally through static cyclic loading tests on RC frame specimens infilled with concrete block masonry. Three scaled (60%) specimens were tested, corresponding to the as-built (CT-1), TCP-retrofitted (RT-TCP) and TRM+XPS-retrofitted (RT-TRM) configurations. The geometry and steel reinforcement detailing of the frame specimens, shown in Fig. 1, aim to reflect a non-seismically designed RC school building that could be found in Korea or Southern Europe. The 60% scaled test specimens have a total height of 1.83 m and a width of 3.0 m. The columns have a square cross-section of 200 mm by 200 mm, with 4 D13 bars as longitudinal reinforcement and shear reinforcement consisting of D6 bars at 120 mm c/c. The main beam had a rectangular T-section, 300 mm deep and 200 mm wide, with a 120 mm deep slab extending 300 mm on each side. The characteristic compressive strength of the concrete for all specimens was f ck = 18 MPa, while the characteristic yield stress was 400 MPa for the primary reinforcement (D13) bars. The infill walls consist of a 60 mm thick concrete block infill wall, 2.6 m in width and 1.53 m in height (aspect ratio 0.59), constructed from B-type cement bricks (190 mm×90 mm×57 mm), with compressive strength of f b = 13.0 MPa. Two different strengthening schemes were tested: RT-TRM was strengthened through TRM jacketing on both sides of the masonry infill (Fig. 2a), including a layer of XPS thermal insulation on one side; RT-TCP was retrofitted with TRM jacket on one face only and a set of six TCP panels on the other face (Fig. 2b). The TCP panels (Fig. 2c) consist of a grid-shaped carbon fibre sheet and a capillary tube (Fig. 2d) embedded in a lightweight mortar, aiming to provide seismic strengthening analogously to TRM, and energy upgrading through radiant heating by circulating hot water through the capillary tube. The materials used in this study, including the TCP panels, carbon fiber sheets, and XPS thermal insulation, were chosen for their proven effectiveness and availability. These materials are standard in the industry, ensuring the practicality and replicability of the retrofit method. Further details of the retrofitting schemes and material properties can be found in Baek et al. (2022). The three specimens were tested using a quasi-static cyclic drift ( δ ) protocol, where each drift cycle was repeated three times and drift values increased from ±0.125%, 0.25%, 0.375%, then from 0.5% up to 1.5% in steps of 0.25% and finally up to 4.0% in steps of 0.5%. The drift percentages applied during the tests correspond to lateral displacements measured at a height of 1.71 m from the base of the columns. Testing was stopped at a drift ratio of 4% or upon the attainment of significant structural damage to the specimens, whichever occurred first. A 250 kN hydraulic actuator (stroke ±125 mm) at the top of the beams was used to apply the lateral load, and lateral displacements were measured at 1.71 m from the base of the columns. A constant axial load of 56 kN was applied on top of the wall to represent gravity loading.