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    GEOTECHNICAL CHARACTERIZATION OF ZEOLITESAND AND BENTONITE-SAND MIXTURES
    (Univ Maribor, 2022) Yildiz, Ozgur; Ceylan, Cigdem
    This paper presents the characterization of pure bentoniteand zeolite-type clays and of various contents mixed with sand. The engineering properties of zeolites, bentonites and sand, which are commonly found in Malatya, Turkey, were evaluated in terms of their suitability for geotechnical applications. The crystallinity and structure of solid specimens of bentonite and zeolite were analysed with X-ray diffraction. Then both soils were mixed with sand in various proportions and the enhancement of the engineering properties was investigated. The properties of the mixtures, such as specific gravity, optimum water content, and dry unit weight mixtures, were initially determined. A set of direct shear tests was carried out to determine the shearstrength parameters of the specimens. As a result of extensive laboratory tests, linear correlations were observed between the water content and the consistency limits with the bentonite and zeolite contents in the sand mixtures. The highest for among each sample tested was achieved with the addition of 50 % bentonite and zeolite (i.e., BS50 and ZS50) as 44 and 38 kPa, respectively. A literature survey was carried out to reveal the test results of similar studies. In addition, using the test results from these literature studies and the current study, an NN-based prediction model was developed. Th e forecast models developed separately for cohesion and internal friction angle had high correlation coefficients: R2 equal to 0.84 for cohesion and R2 equal to 0.78 for the friction angle.
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    Influence of input motion and surface layer properties on seismic site response: A stochastic simulation method-based MLR model
    (Wiley, 2023) Yildiz, Ozgur
    Seismic site response analyses are simulations in which the effects of geological conditions on seismic waves are examined. The uncertainties that make these analyses crucial are defined as the source of motion, the travel path of seismic waves, and geological conditions. In this study, a series of non-linear seismic response analyses were performed using data from site investigation studies. The results of non-linear analyses performed under earthquakes with different characteristics based on real soil data were investigated in terms of acceleration time histories and response spectra. The relationship between site response with the surface layer properties and input motion properties used in the simulations was examined in a parametrical manner. Based on the results obtained, Monte Carlo simulation, which is a stochastic data simulation method, was performed. Additionally, multiple regression and variance analysis (ANOVA) was performed on the dataset created by both site response analysis and stochastic simulations. The MLR model displayed highly accurate results with a coefficient of determination, R-2 of 0.9763, and a standard error of 0.109. The efficiency level of the independent variables used as input parameters in the simulations on the dependent variable, AF was examined. It was revealed that the coefficient of lateral earth pressure at rest (K-o), earthquake motion (i.e., PGA of input motion) and surface layer thickness (d(surface)) from the soil properties had the highest effect on the amplification factor.
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    Seismic Performance Assessment of an RC Building Due to 2023 Türkiye Earthquakes: A Case Study in Adıyaman, Türkiye
    (Mdpi, 2025) Bassurucu, Mahmut; Yildiz, Ozgur; Kina, Ceren
    The 7.7 and 7.6 magnitude Pazarc & imath;k and Elbistan earthquakes that struck Kahramanmara & scedil; on 6 February 2023 caused widespread structural damage across many provinces and are considered rare in seismological terms. While many reinforced concrete (RC) buildings designed under current earthquake regulations sustained significant damage, some older RC buildings with outdated designs sustained only moderate damage. This study aims to analyze the seismic performance of such older RC buildings to understand why they did not collapse or suffer severe damage. An 8-story RC building in Ad & imath;yaman province, damaged by the earthquake, was considered for analysis. The region's seismicity and local site conditions were assessed through borehole operations, geotechnical laboratory tests, and seismic field tests. The soil profile was modeled, and one-dimensional seismic site response analyses were performed using records from nearby stations (TK 4615 Pazarc & imath;k and TK 4612 G & ouml;ksun stations) to determine the foundation-level earthquake record. Nonlinear static pushover analysis was carried out via SAP2000 and STA4CAD, utilizing site response analysis and test results taken from the reinforcement and concrete samples of the building. The findings, compared with the observed damage, provide insights into the performance of older RC buildings in this region.
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    Shaking table tests on geotechnical seismic isolation for medium-rise buildings using EPS beads-sand mixtures
    (Springer, 2023) Edincliler, Ayse; Yildiz, Ozgur
    The mixture of sand-expanded polystyrene (EPS) beads has emerged as an alternative seismic isolation geomaterial due to its high compressibility and energy absorption capacity features. The objective of this study is to determine the effectiveness of a new proposed geotechnical seismic isolation material, EPS beads-sand mixtures, on the seismic performance of the medium-rise buildings by shake table tests. A 1/10 scaled five-story building model was used in order to determine the effects of the EPS-beads as an isolation material. The seismic isolation layers were created surrounding the foundation of a mid-rise building model with sand-EPS beads mixtures at varying thicknesses. The influence of various parameters, particularly the earthquake characteristics of input motions, the EPS beads content, and the thickness of the isolation layer were investigated. As a result of the extensive experimental program, it was revealed that the EPS40 with the 15 cm isolation thickness significantly reduced the peak accelerations and the inter-story drifts. The utilization of the EPS beads-sand mixture layer under the foundation may be accepted as an alternative seismic isolation material. In addition, the results of this first study were also evaluated according to rubber-sand mixtures as another GSI material in the literature. The results showed that the proposed GSI material is very sensitive to the changes of content and earthquake characteristics. This study is very important as it shows that EPS beads-sand mixtures can be accepted as a potential seismic isolation material.
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    Soil-structure interaction analysis of Celebiaga Mosque, Pertek-Turkiye
    (Pontificia Univ Catolica Chile, Escuela Construccion Civil, 2022) Yildiz, Ozgur; Dogan, Ebru
    After the construction of the Keban Dam, some settlements with historical, cultural, and natural value were flooded. A scientific committee consisting of academicians and public authorities decided to the relocation of the buildings including the historical Celebiaga Mosque. In this study, the seismic soil-structure interaction analysis of the historical Celebiaga Mosque, which was dismantled and reconstructed in a separate region due to the construction of the Keban Dam was carried out. The analysis of the masonry mosque was performed with the SAP2000 finite element analysis software. The Winkler foundation model was used to idealize the soil environment on which the historical mosque was built. The effects of soil-structure interaction on historical masonry mosque were examined in terms of transmitted acceleration, response spectra, and lateral displacement at various heights of the structure. Depending on the results of the analysis, the effects of soil-structure interaction of a reconstructed historical masonry building were investigated. PGA was obtained as 0.51g at the flag level of the minaret under the Kocaeli earthquake and 0.94g under the Sivrice earthquake. Again, the maximum horizontal displacements of the minaret at the flag level were obtained as 11 cm and 8.5 cm under the Kocaeli and Sivrice earthquakes. The behavior of historical masonry structures under earthquake loads has been interpreted by considering the geological conditions.
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    Stabilization of Zeolite and Bentonite with Sewage Sludge Ash
    (Budapest Univ Technology Economics, 2023) Yildiz, Ozgur; Ceylan, Cigdem
    In this study, it is aimed to evaluate the wastewater sludge supplied locally at 100 tons/day in the investigation area. In this context, the geotechnical properties of bentonite, zeolite-type clays and sands, which are common in the investigation area, were determined by mixing with sewage sludge ash (SSA) in specified ratios. Grain size distribution and specific gravity of pure materials and mixtures were determined. Direct shear tests, permeability tests, consistency limits tests, modified proctor tests and PH determination tests were performed with the mixtures. Soils were mixed with 0.5, 7.5, 10 and 12.5 percent SSA in order to determine the physical, chemical and mechanical properties. Mixtures of sand with 40% bentonite (i.e., BS40) and sand with 40% zeolite (i.e., ZS40) were used as host materials for SSA inclusion. As a result of extensive laboratory studies, it was observed that the engineering properties of the specimens changed significantly as a result of the 7.5% and 12.5% mixture of SSA. BS40/SSA7.5 and ZS40/SSA12.5 samples from the mixtures reached 83 kPa and 80 kPa maximum shear strength under 200 kPa normal pressure. The maximum unit weight of specimens was achieved by BS40/S5 and ZS40/S5 specimens as 1.72 and 1.82 g/cm3, respectively. With the addition of SSA, the hydraulic permeability of the mixtures decreased to an order of 10E-8 (cm/s) for BS40/SSA12.5 and ZS40/12.5 specimens. Experimental studies have provided significant engineering and environmental benefit in the evaluation of sewage sludge ash, which is inevitable in residential areas.
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    Use of a Biopolymer for Road Pavement Subgrade
    (Mdpi, 2023) Cabalar, Ali Firat; Akbulut, Nurullah; Demir, Suleyman; Yildiz, Ozgur
    This paper presents an extensive series of laboratory works and a prediction model on the design of a road pavement subgrade with Xanthan Gum (XG) biopolymer. The experimental works were carried out using mixtures of conventional aggregate for road pavement construction and XG at the ratios of 0%, 1%, 2%, and 5%, by dry weight. Unconfined compressive strength (UCS) and California bearing ratio (CBR) tests were conducted during the experimental works at the end of the various curing periods (4, 8, 16, and 32 days). An example of an improvement in the UCS values for a specimen with 5% XG addition tested at the end of 4-daycuring yields about a 200% increment by the end of a 32-daycuring. The CBR values of clean aggregates were found to be increased by about 300% by 5% XG addition for all curing periods applied. Furthermore, the energy absorption capacity of the aggregates was observed to be increased significantly by both XG inclusion and curing period. Moreover, scaled conjugate gradient (SCG) training algorithm-based models developed for the prediction of CBR and UCS test results displayed a very high estimation performance with the regression coefficients of R-2 = 0.967 and R-2 = 0.987, respectively. Evidently, XG biopolymer is provably of use as an alternative inclusion in road pavement subgrades constructed with conventional aggregates.