Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 3Citation - Scopus: 3A Novel Hybrid Thin Jacketing Method for Seismic Retrofitting of Substandard Reinforced Concrete Columns(Elsevier Ltd, 2025) Narlitepe, Furkan; Kian, Nima; Demir, Ugur; Demir, Cem; Ilki, AlperThis paper introduces a novel hybrid thin jacketing method for seismic strengthening of substandard reinforced concrete (RC) columns for which structural repair mortar along with carbon fiber reinforced polymer (CFRP) and longitudinal steel bars are utilized. The method involves three application phases comprising a) removing the cover concrete, b) re-forming the cover concrete with structural repair mortar just after installing extra longitudinal steel bars c) transverse wrapping of CFRP sheets. The effect of using different types of structural repair mortar and its application process are other test parameters taken into account in this study. To evaluate the efficacy of the proposed method, a comprehensive experimental program was conducted, consisting of six largescale RC column specimens with square and rectangular cross-sections. For all of the specimens tested under a simultaneous constant axial load and reversed cyclic lateral loading, three main properties representing existing substandard RC columns such as a) insufficient transverse reinforcement, b) high axial load ratio (0.75) and, c) relatively high shear force corresponding to moment capacity to shear capacity ratios between 0.60 and 0.80, were considered. The responses of specimens were specified in terms of the lateral load-displacement curves, stiffness variation, ductility ratios, damage progression, and energy dissipation. The experimental results demonstrated that in case the retrofitting method is properly applied, the strengthened columns exhibit satisfactory performance in terms of strength and ductility with a remarkable improvement with respect to the substandard columns. Furthermore, a numerical study was conducted to validate the experimental results by using the OpenSees framework.Article Citation - WoS: 3Citation - Scopus: 3Seismic Testing and Modeling of Full-Scale Substandard Rc Columns Retrofitted With Sprayed Gfrm With and Without Basalt Mesh Under High Axial Compression and Shear Demand(Asce-Amer Soc Civil Engineers, 2025) Kian, Nima; Demir, Ugur; Ates, Ali Osman; Celik, Oguz C.; Ilki, AlperThis study presents the experimental and analytical hysteretic behaviors of eight full-scale RC square and rectangular columns. The columns were designed to have different shear spans that represent: (1) a column that complies with the Turkish Government Ministry of Reconstruction and Resettlement's ( 1975) seismic design code, Turkish Seismic Design Code (TSDC); (2) a substandard column; and (3) two sprayed glass fiber-reinforced mortar (GFRM)-retrofitted counterparts of the substandard column with and without basalt mesh. The substandard columns were designed to be subjected to relatively high shear ratios (i.e., the ratio of the shear force that corresponds to the moment capacity to shear strength of the cross section) up to 0.85 and with a high axial load-to-capacity ratio of 0.75. All columns were tested under constant axial load and reversed cyclic lateral displacement excursions. The results revealed that the columns that complied with the TSDC showed satisfactory behavior for seismic performance, and the performance of the substandard columns was extremely poor. However, the hysteretic performance of the substandard columns that were subjected to high axial stress and shear significantly improved after the proposed retrofitting. Finally, a numerical model was developed in OpenSees to reproduce the hysteresis curves of the specimens. The slip of the longitudinal bars at the column-foundation interface, strain penetration into the foundation, and buckling of the longitudinal bars in compression were accounted for in the modeling. The results are in good agreement with the experimental hysteresis curves. The performance levels of the columns are further specified, and the predictions of the current seismic codes were analyzed: (1) the European Committee for Standardization's 2005 code, Eurocode 8: Design of structures for earthquake resistance; Parts 1-3: Strengthening and repair of buildings (EC8-3); and (2) the Turkish Government Ministry of Interior Disaster and Emergency Management Authority's 2018 code, Turkish Building Earthquake Code (TBEC). The TBEC provided more accurate estimates of plastic rotation capacities for substandard specimens. In contrast, EC8-3 overestimated the plastic rotation capacity when shear stresses were relatively high due to lower shear span-to-depth ratios (a/d).Conference Object Citation - WoS: 1Citation - Scopus: 2Seismic Performance of Substandard Rc Columns Retrofitted With Sprayed Gfrm(Springer, 2022) Kian, Nima; Demir, Uğur; Demir, Cem; Maraşlı, Muhammed; İlki, AlperThere is a myriad amount of substandard reinforced concrete (RC) buildings in developing countries that do not comply with the requirements and instructions of the current building design codes. In particular, columns in these substandard buildings demonstrate unsatisfactory and undesired behavior against lateral loads, mainly due to low concrete compressive strength and poor reinforcement detailing. The problem is exacerbated when the axial load ratio (ratio of applied axial load to the axial load capacity) and/or the shear ratio (ratio of shear force corresponding to moment capacity (Ve) to the shear capacity (Vr)) is/are high, leading to brittle failure modes. In this study, three full-scale substandard RC columns subjected to high axial load ratio of 0.75 were tested under constant axial load combined with reversed cyclic lateral displacements. Shear ratio (Ve/Vr) of the substandard columns were 0.75 and 0.82 according to ACI 318-19 (ACI 318 (2019) Building Code Requirements for Structural Concrete. American Concrete Institute, Farmington Hills, MI, USA) and (Turkish Building Earthquake Code (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey), respectively. According to the TBEC (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey), columns had a high Ve/(fctmbd) ratio of 1.12, where, fctm, b, and d are the direct tensile strength of concrete, width of the cross-section, and effective depth of the section. The ratio of transverse reinforcement to minimum required transverse reinforcement according to the ACI 318-19 (ACI 318 (2019) Building Code Requirements for Structural Concrete. American Concrete Institute, Farmington Hills, MI, USA) and TBEC (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey) was 0.19 and 0.77, respectively. Two of the columns were retrofitted with an innovative, cost-effective, and easily-applicable strengthening method, through external jacketing with sprayed glass fiber reinforced mortar (GFRM) of different characteristics. The remaining column was tested as the reference specimen to evaluate the efficiency of the strengthening method. The test results demonstrated the extremely poor performance of the reference substandard column as well as the remarkable lateral load capacity and ductility improvement provided by the adopted novel strengthening approach.