Medine Ispir

Seismic retrofitting of existing reinforced concrete (RC) columns with fiber-reinforced polymer (FRP) jackets typically requires removing plaster to ensure direct bonding. Although widely practiced, plaster removal increases labor, cost, and environmental impact and can damage the weak concrete surfaces common in substandard buildings. Previous experimental studies have mostly examined FRP confinement applied directly to concrete; however, the axial behavior of columns strengthened without plaster removal remains largely unexplored. In particular, the combined effects of plaster thickness, plaster strength, and FRP jacket configuration have not been systematically evaluated for square columns with retained plaster. This study addresses this gap by experimentally investigating the monotonic axial behavior of plastered concrete columns retrofitted with carbon FRP (CFRP) jackets. Twenty unreinforced square columns (275 × 275 × 550 mm), cast with low-strength concrete (approximately 10 MPa), were tested under axial compression. The parameters varied were plaster thickness (12.5, 25.0, and 37.5 mm), plaster compressive strength (approximately 4.5 and 9.0 MPa), and CFRP jacket configuration (one or two layers). Test results show that, within the engineering-relevant axial strain range (≤1.5%), CFRP jacketing over plastered surfaces effectively maintains the axial load-carrying capacity regardless of plaster properties, demonstrating adequate confinement. These findings confirm the feasibility of CFRP retrofitting without plaster removal and provide a practical framework for strengthening RC members constructed with low-strength concrete. A new constitutive model was developed to represent the axial stress–strain response of plastered CFRP-jacketed concrete, explicitly incorporating plaster thickness, plaster strength, and CFRP jacket configuration. The proposed model captures the experimental behavior with high accuracy and offers a reliable tool for the design and assessment of plaster-interlayered CFRP-strengthened columns.

1. Historic buildings are a fundamental part of our cultural heritage. They host tangible and intangible cultural assets, including the memory of previous generations, and are places where communit...

Seismic strengthening of existing reinforced concrete (RC) columns often involves applying carbon fiber-reinforced polymer (CFRP) jackets, which typically requires the removal of existing plaster layers to ensure direct bonding. While this practice is widely adopted, it increases construction costs, prolongs retrofit duration, generates considerable plaster waste, and may damage already low-strength concrete substrates. Previous experimental research has mainly focused on CFRP jackets applied directly to bare concrete, demonstrating their effectiveness in improving load-carrying capacity and ductility. However, the combined effects of plaster thickness, plaster strength, and CFRP jacket configuration on the seismic performance of square-section columns with retained plaster layers remain insufficiently explored. This study experimentally investigates the seismic performance of eight full-scale substandard RC columns (300 × 300 × 1350 mm) constructed with low-strength concrete (~10 MPa) and widely spaced transverse reinforcement, tested under reversed cyclic lateral loading while maintaining constant high axial load ratio of 60%. The experimental variables include three plaster thicknesses (12.5, 25, and 37.5 mm), two plaster compressive strengths (~3.5 and ~8.5 MPa), and single- or double-layer CFRP jackets. Test results demonstrate that retaining the plaster layer does not prevent significant ductility enhancement; in several cases, plastered CFRP-jacketed specimens achieved drift capacities comparable to or exceeding those of unplastered counterparts. These findings provide new experimental insights into the feasibility and effectiveness of CFRP jacketing over plastered concrete surfaces, highlighting a practical retrofitting approach that minimizes construction time, and environmental impact while maintaining structural performance.

Historical minarets are generally vulnerable to earthquakes because of their poor-quality materials and high slenderness. The objective of this work is to utilize the methodology employed for seismic fragility curves to analyze historical brick minarets, specifically focusing on a specific instance minaret. For this, the minaret of the Hocaalizade Mosque, built in Bursa during the Early Ottoman Period, was chosen. Using the software Abaqus v6.13, the minaret’s finite element model was constructed utilizing shell elements for the minaret and the walls of the mosque, and wire elements for the stair. The model was updated in accordance with the operational modal analysis (OMA) that was carried out in the field. Subsequently, IDA curves were generated for the minaret using Nonlinear Incremental Dynamic Analysis, utilizing 11 actual ground motion records with two horizontal components. A probabilistic approach was utilized in order to acquire the fragility curves for each performance level, which included limited damage, controlled damage, and collapse prevention. The outcomes of nonlinear time history analyze indicate that the minaret sustains damage mostly in two areas: between the transition and shaft, and/or between the balcony and the upper part. The analyses yielded fragility curves using two intensity measures as spectral acceleration and peak ground acceleration. The statistical assessment and regression analyses between each intensity measure and the probability of exceedance indicate that both intensity measures can be considered appropriate for the studied minaret. This minaret experiences the collapse prevention limit when the spectral acceleration (peak ground acceleration) exceed ∼0.27 g (0.13 g ), respectively, with a ∼50% likelihood.

Post-earthquake reconnaissance of engineering structures aims to collect the essential data required for forensic investigations of failures. These investigations inform time-critical repair, stabilisation and demolition decisions after an earthquake. Current reconnaissance procedures rely on visual observations and manual surveying, which do not provide adequate data for the forensic analysis of historic masonry structures. This study shows how an alternative form of data, point clouds from laser scanning and photogrammetry, can be used to conduct detailed forensic work. Case studies from the 2023 Turkey earthquakes are used to illustrate how point clouds were employed to 1) quantify the geometry of load-bearing systems, 2) assess construction quality, 3) detect geometric distortions and defects, and 4) provide data to generate and evaluate numerical models. The examples highlight the new insight provided by this alternative form of data. The dataset collected as a part of this study is shared open access to enable further investigations: https://github.com/Yilong-Yang/Shared-Data---BEE-2025.

The aim of this study is to define the cyclic axial behavior of hybrid FRP (fiber reinforced polymer)-confined concrete based on the results of an experimental study presented here. Two different types of fiber sheets with different ultimate tensile strain capacities were used together in a suitable epoxy resin matrix to confine concrete. The inner and outer jackets of the concrete confinement were constituted with carbon (or glass) sheets with a relatively low tensile strain capacity and polyethylene terephthalate (PET) sheets with a high tensile strain capacity. PET fibers, which are a relatively new type of fiber, are made from recycled plastics. By varying the number of layers of the outer fiber sheet, different combinations were formed for the hybrid jackets. To characterize the cyclic axial behavior of hybrid FRP-confined concrete, experimental data were utilized to obtain the axial stress–strain relationship and dilation behavior. Based on the results, a stress–strain model for the envelope curve of the cyclic response of hybrid FRP-confined concrete is proposed.

As the first study reported in the literature on the axial behavior of noncircular high-performance fiber-reinforced cementitious composite (HPFRCC) members externally jacketed by fiber-reinforced polymer (FRP) sheets, the aim of this paper is to experimentally identify the axial behavior characteristics of these members under compression. The test results of 21 specimens showed that the axial and lateral deformation characteristics of FRP-jacketed HPFRCC members are significantly different from those of FRP-confined conventional concrete members. Small voids in HPFRCCs due to the presence of fine aggregates and reduced crack widths due to the contribution of steel fibers limit the transverse deformations remarkably until the axial strain value is approximately 0.0035. The test results show that the dilation ratio increases after the axial strain reaches this value. Then, the external FRP jacket begins to noticeably affect the behavior, resulting in a significant improvement in the axial strength and deformation capacity. However, since the external FRP jacket is activated after relatively large axial strains, significant strength degradations can occur before the FRP jacket provides an effective contribution. As the stiffness of the FRP jacket increases, the strength degradation experienced before the activation of the FRP jacket decreases. Furthermore, the predictions of five available models that were developed for modeling the axial behavior of FRP-confined concrete are examined through comparisons with test results.