İnşaat MühendisliğiCivil Engineeringhttps://hdl.handle.net/20.500.12511/41622024-03-29T05:01:25Z2024-03-29T05:01:25ZFuzzy standardized precipitation index (FSPI) for drought early warning procedureŞen, Zekâihttps://hdl.handle.net/20.500.12511/123882024-03-22T06:31:08Z2024-01-01T00:00:00ZFuzzy standardized precipitation index (FSPI) for drought early warning procedure
Şen, Zekâi
There are several standardized meteorological, hydrological, agricultural, and environmental indices for drought classification into a set of dry categories all of which are derived from the basic concept of standardized precipitation index (SPI). Almost all these indices are based on crisp (bivalent) logic where boundary limits between neighboring categories are numbers without transboundary inclusiveness. The SPI procedure depends on the standard normal (Gaussian) probability distribution function (PDF) with zero mean and standard deviation equal to one. This paper proposed fuzzification of the SPI limits among categories for the inclusion of more than one category with different membership degrees. This method is referred to as the fuzzy SPI (FSPI) procedure, which provides drought tracing possibility and categorization. At the end for a numerical value, one can defuzzify the fuzzy result through defuzzification methods. FSPI provides preliminary warning system in terms of two or more fuzzy rule propositions and categories. Thus, one can know the logical alternatives of the drought behavior of a given hydro-meteorology variable. The application of the FSPI is presented for New Jersey State wise and Istanbul annual precipitation records.
2024-01-01T00:00:00ZAssessing wet and dry periods using Standardized Precipitation Index Fractal (SPIF) and polygons: A novel approachŞen, Zekâihttps://hdl.handle.net/20.500.12511/123472024-03-11T05:16:59Z2024-01-01T00:00:00ZAssessing wet and dry periods using Standardized Precipitation Index Fractal (SPIF) and polygons: A novel approach
Şen, Zekâi
In the open literature, there are numerous studies on the normal and extreme (flood and drought) behavior of wet and dry periods based on the understanding of the standard precipitation index (SPI), which provides a series of categorizations by considering the standard normal (Gaussian) probability distribution function (PDF). The numerical meaning of each categorization assessment is quite lacking in terms of future predictions of wet and dry period duration based on historical records. This paper presents a new approach for calculating possible formations of future wet and dry period durations based on historical records through an effective fractal geometric forecasting approach. The essence of the proposed methodology is based on the number of dry periods (steps) of non-overlapping monthly duration along consecutive broken line paths in the SPI classification for wet and dry period durations. It has been observed that the plot of periods on double logarithmic paper falls along a straight line against the number of such periods, implying a power function, which is the essence of fractal geometry. Extending the empirically derived straight line provides the number of periods that may occur in the future over a range of SPI levels. This methodology is referred to as SPI fractal (SPIF), and the classic SPI classification is converted into SPIF wet and dry polygons, which provide additional information about the drought period number within a valid polygonal area, compared to the classic SPI results. The wet and dry period features of any hydro-meteorology time series are constrained in SPIF polygons. The application of the methodology was carried out on monthly rainfall records on the European side of the Istanbul Florya meteorological station in Turkey.
2024-01-01T00:00:00ZCross-sectional warping and precision of the first-order shear deformation theory for vibrations of transversely functionally graded curved beamsArıbaş, Ümit NecmettinAydın, MeteAtalay, MertOmurtag, Mehmet Hakkıhttps://hdl.handle.net/20.500.12511/121302024-01-12T08:41:12Z2023-01-01T00:00:00ZCross-sectional warping and precision of the first-order shear deformation theory for vibrations of transversely functionally graded curved beams
Arıbaş, Ümit Necmettin; Aydın, Mete; Atalay, Mert; Omurtag, Mehmet Hakkı
The warping may become an important factor for the precise transverse vibrations of curved beams. Thus, the first aim of this study is to specify the structural design parameters where the influence of cross-sectional warping becomes great and the first-order shear deformation theory lacks the precision necessary. The out-of-plane vibrations of the first-order shear deformation theory are compared with the warping-included vibrations as the curvature and/or thickness increase for symmetric and asymmetric transversely-functionally graded (TFG) curved beams. The second aim is to determine the influence of design parameters on the vibrations. The circular/exact elliptical beams are formed via curved mixed finite elements (MFEs) based on the exact curvature and length. The stress-free conditions are satisfied on three-dimensional (3D) constitutive equations. The variation of functionally graded (FG) material constituents is considered based on the power-law dependence. The cross-sectional warping deformations are defined over a displacement-type FE formulation. The warping-included MFEs (W-MFEs) provide satisfactory 3D structural characteristics with smaller degrees of freedom (DOFs) compared with the brick FEs. The Newmark method is used for the forced vibrations.
2023-01-01T00:00:00ZPre-earthquake fuzzy logic-based rapid hazard assessment of reinforced concrete buildingsMangır, AtakanOkumuş, Vefahttps://hdl.handle.net/20.500.12511/116202023-11-15T07:33:40Z2023-01-01T00:00:00ZPre-earthquake fuzzy logic-based rapid hazard assessment of reinforced concrete buildings
Mangır, Atakan; Okumuş, Vefa
The main purpose of this paper is to present a rapid building assessment fuzzy logic (FL) modelling for risk assessment based on expert construction engineering verbal informatics. Before an earthquake, a set of input expert assessment variables are transformed into five types of hazard categorization as "no damage", "slight damage", "moderate damage", "severe damage", and "collapse". Main variables are reported by expert engineers based on visual inspection of structural components in addition to the building location's peak ground velocity (PGV) micro zonation numerical value, soil type and building's material information. Each input variable and output hazard class is fuzzified. A valid set of fuzzy rule base components is written based on input variables, each of which has an appropriate output hazard class. The fuzzy hazard assessment model has input and output variables in terms of fuzzy sets. Thus, the overall model output is in the form of a fuzzy set and then defuzzified to find the percentage of each hazard class for a single building. The application of this fuzzy logic model is presented for twenty existing reinforced concrete buildings, and the final hazard categories of these buildings are presented with interpretations and recommendations.
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