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Article Citation - WoS: 5Citation - Scopus: 7Lessons Learned From Four Recent Turkish Earthquakes: Sivrice-Elazığ, Aegean Sea, and Dual Kahramanmaraş(Springer, 2024) Tunc, Goekhan; Mertol, Halit Cenan; Akis, TolgaT & uuml;rkiye is located in an earthquake-prone region where almost all of its population resides in risky areas. In the past 100 years, there has been a strong earthquake every two years and a major one every 3 years. This study investigates the impact of four recent earthquakes, that occurred between 2020 and 2023, on reinforced concrete (RC) buildings. The first, Sivrice-Elaz & imath;& gbreve;, struck the eastern part of T & uuml;rkiye on January 24, 2020, with a moment magnitude of Mw = 6.8. The second, the Aegean Sea, hit the western part of the country on October 30, 2020, with an Mw of 6.6. The third and fourth are the February 6, 2023 dual Kahramanmara & scedil; earthquakes with Mws of 7.7 and 7.6, which struck the eastern part of T & uuml;rkiye approximately 9 h apart. Immediately following these earthquakes, a technical team investigated each of the damaged areas. This study summarizes their findings on RC buildings. It was discovered that the majority of the collapsed or severely damaged RC buildings were constructed before 2000. The main reasons for this included technological limitations, specifically on producing high-quality concrete, as well as a lack of public policies and enforced laws in the construction sector to maintain an acceptable international standard. Furthermore, the damage patterns of buildings from these four earthquakes indicated poor workmanship, low material quality, improper structural framing, a common appearance of soft and weak stories, the inadequate use of shear walls, and defective reinforcement configuration. The significance of soil studies and the enforcement of building inspections are also discussed, along with the earthquake codes. The study concludes that the maximum peak ground accelerations from the dual Kahramanmara & scedil; earthquakes were almost triple the code-prescribed values. Therefore, it is recommended that the current mapped spectral acceleration values be revised and that buildings constructed before 2000 should be prioritized while determining their structural performances.Article Citation - WoS: 4Citation - Scopus: 4A Site Survey of Damaged Rc Buildings in Izmir After the Aegean Sea Earthquake on October 30, 2020(Croatian Soc Civil Engineers-hsgi, 2023) Mertol, Halit Cenan; Tunc, Gokhan; Akis, TolgaAn earthquake with a magnitude of Mw = 6.6 and a depth of approximately 16.5 km occurred on 30 October 2020 off the cost of Samos, a Greek island 35 km southwest of Seferihisar, a town in Izmir. The earthquake caused several collapses and severe structural damage in approximately 6,000 buildings, specifically in the Bayrakli District in Izmir Bay. This paper presents the observations and findings of a technical team that visited the earthquake -affected areas immediately after the earthquake. Eleven partially or fully collapsed and several severely damaged reinforced concrete buildings were investigated. Based on the site investigations, we observed that almost all of the collapsed or severely damaged reinforced concrete buildings in the region were built between 1975 and 2000. Site observations also confirmed that the construction of these collapsed or damaged buildings did not conform to the requirements outlined in the Turkish Earthquake Codes used at the time. The failures and severe damage to buildings in earthquake-affected areas are primarily related to inadequate reinforcement configuration, poor material quality, the absence of geotechnical studies, and framing problems related to their lateral load-carrying systems. Therefore, it is recommended that all the buildings located in and around Izmir Bay, particularly those built between 1975 and 2000, be structurally evaluated to prevent any further loss of life and property during future earthquakes.Article Citation - WoS: 9Citation - Scopus: 10Influence of Cement Replacement by Calcinated Kaolinitic and Montmorillonite Clays on the Properties of Mortars(Springer Heidelberg, 2023) Al-Noaimat, Yazeed A. A.; Akis, TolgaThis study aims to investigate the decomposition and pozzolanic reactivity of two different clays (kaolinitic and montmorillonite) from different origins and to determine their effects after calcination on the properties of cement mortars when used to replace Portland cement partially. Mineralogical and chemical compositions of the clay samples were determined using XRD (X-ray Diffractometer) and XRF (X-ray Fluorescence) tests, respectively. TG-DTA (Thermogravimetry-Differential Thermal Analyses) was used to determine the temperature profiles and the burning temperatures of the clays. The density and fineness of the burnt clays were also determined. In order to investigate the optimum material properties, different burning temperatures and replacement levels were considered. It was found that for all temperatures, the two burnt clays possess good pozzolanic activity. The highest compressive strength and lowest water absorption capacity were achieved when the clay determined as kaolinitic was burned at 700 & DEG;C and with 10% replacement level. While for the clay determined as montmorillonite, the optimum properties were obtained at 700 & DEG;C with a 20% substitution level. Kaolinite had better pozzolanic reactivity than montmorillonite, achieving higher strength performance with lower water absorption when partially replaced with cement. Moreover, it had compressive strength values even higher than plain cement.Article Citation - WoS: 54Citation - Scopus: 58Investigation of Rc Buildings After 6 February 2023, Kahramanmaras, Turkiye Earthquakes(Mdpi, 2023) Mertol, Halit Cenan; Tunc, Gokhan; Akis, Tolga; Kantekin, Yunus; Aydin, Ishak CanTwo major earthquakes struck Pazarcik and Elbistan, towns in Kahramanmaras, Turkiye, on 6 February 2023, approximately 9 h apart. The first earthquake, recorded at 04:17 local time, had a M-w = 7.7, with a focal depth of 8.6 km. At 13:24 local time, a second earthquake occurred with M-w = 7.6 at a focal depth of 7 km, approximately 90 km north of the first one. A total of 11 provinces were severely affected by these earthquakes. As of 15 April 2023, they caused close to 51,000 deaths and almost 215,000 completely destroyed/severely damaged buildings. At some locations, the largest horizontal peak ground acceleration (PGA) values of the first and second earthquakes exceeded the code-generated PGAs by almost 3 and 1.75 times, respectively. A technical team visited these areas within 15 h of the first earthquake. The purpose of this article is to present their observations, findings, and the characteristics of the two earthquakes, with comprehensive site survey results supported by photographs. This study concludes that most of the collapsed and severely/moderately damaged buildings in the region were built between 1975 and 2000, when site inspections were rare or non-existent. In addition to the high PGAs recorded in these earthquakes, it was verified that the design and construction of these buildings did not fully comply with the earthquake codes valid at the time. The collapsed buildings and their damage patterns confirm inadequate development length, violation of bending stirrup ends at 135 & DEG;, deficiencies in construction materials and reinforcement configuration, noncompliance with confinement zones, violation of the strong beam-stronger column analogy, and issues related to building inspection. Based on the extent of the damage, it is strongly recommended that the structural performance inspection of all other buildings located near major fault lines, specifically those constructed between 1975 and 2000, should be completed. Since these earthquakes generated much higher PGAs, which is believed to be one of the main reasons for the extensive damage, a re-evaluation of all other PGAs along major fault lines is also recommended.