Master Tezleri

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Analysis and modelling of a novel approach for the interrogation unit of fiber Bragg grating sensors using optical frequency domain reflectometry techniques
(Izmir Institute of Technology, 2014) Pala, Deniz; Yüksel Aldoğan, Kıvılcım
The main purpose of this thesis is to demonstrate the feasibility of using polarization properties of FBGs interrogated by OFDR for quasi-distributed sensing applications. A fiber Bragg grating (FBG) is a constant and periodic refractive index value modulation within the core along an optical fiber. This modification is generally obtained by exposing the fiber core of a photosensitive optical fiber to an intense ultraviolet (UV) interference pattern. At the fabrication process of Bragg gratings, only one side of the fiber expose to UV light. As a result, refractive index change is not constant at the cross section of fiber. This non-uniformity on the refractive index gives rise to photo-induced birefringence which combines with the birefringence resulting from the slightly elliptical shape of the optical fiber and creates a global birefringence value. In the presence of the birefringence, the reflection (transmission) spectrum of Bragg grating is degenerated into two reflection (transmission) spectra corresponding to a pair of orthogonal polarization modes (x and y modes). The ratio between maximum and minimum optical transmitted power of these modes are defined as Polarization Dependent Loss (PDL). We analyzed the reflection spectrum, transmission spectrum and the PDL of the cascaded FBGs interrogated by an OFDR by the way of simulations. Based on the simulation results, we demonstrated the feasibility of a novel FBG interrogation method which can be implemented in quasi-distributed strain sensors embedded into composite materials.
Antiproliferative properties of 2'-alkoxymethyl substituted klavuzon derivatives
(Izmir Institute of Technology, 2017-07) Yıldız, Mehmet Salih; Çağır, Ali; Pesen Okvur, Devrim
One of the main objectives of studies on anticancer agents is that the agent is expected to show a high cytotoxic activity on cancer cells and show a less cytotoxic effect on the contrary in healthy cells or never show cytotoxic activity. (R)- goniothalamin, isolated from the Goniothalamus plant, is a styryl lactone and has been found to have a selective antiproliferative property on cancer cells in studies conducted. The Michael acceptor feature in the structure of goniothalamin is thought to be covalently bonded to the nucleophilic side chains of the enzymes and show activity in this way. In previous studies, it has been shown that 1-naphthyl substituted 5,6-dihydro- 2H-pyran-2-one derivatives and 4'-methyl klavuzon derivatives exhibit higher cytotoxic activity on cancer cells than goniothalamin. In this study, antiproliferative properties of newly synthesized 2'-alkoxymethyl substituted klavuzon derivatives have been examined and MIA PaCa-2 pancreatic cancer cell lines and HPDEC pancreatic healthy cell lines were used. MTT cell viability tests were performed at the first step of this study. As a result of this study, it has been observed that the 2'-isobutoxymethylklavuzon derivative has selective cytotoxic activity on the MIA PaCa-2 cell line. It showed activity at lower concentrations than goniothalamin. Cytotoxic activities of the compounds are associated with the size of the R group at position 2’-. Methoxymethyl substituted the worst selective activity among these compounds whereas isobutoxy derivative the best selective one. In the second stage of the study, the inhibition on topoisomerase I enzyme was studied. The 2'-alkoxymethyl klavuzon derivatives were found to have Topo I enzyme inhibition properties depending on concentration and time manner. The study continued with choices methoxy and isobutoxy derivatives and these two compounds caused an arrest at G1 phase and DNA damage. Also, isobutoxy derivative induced apoptosis in the MIA PaCa-2 pancreatic cancer cell lines.
Application of artificial neural networks to structural reliability problems
(01. Izmir Institute of Technology, 2023-06) Köroğlu, Fahri Baran; Aktaş, Engin; Maguire, Marc
The contemporary approach in structural engineering indirectly addresses uncertainties arising from load and resistance parameters by using safety factors. To consider these uncertainties in structural engineering, it is necessary to incorporate their statistical properties into the analysis and design process. However, this approach requires the calculation of challenging multi-fold probability integrals. Approximate methods known as FORM and SORM have been developed as an alternative to calculating those integrals. Unfortunately, these methods might have accuracy and convergence problems depending on the problem at hand. Simulation-based structural reliability methods have been developed to overcome the problems associated with approximate methods. The main problem with these methods is that they are often computationally expensive when along with finite element analysis, or it is hard to implement them when a more specific method is chosen to reduce computational costs. In this study, artificial neural networks have been applied to structural reliability problems to obtain accurate probability estimates with low computational cost. A special type of learning algorithm called Bayesian Regularization was used in the training of artificial neural networks. Additionally, details of the application of artificial neural networks to structural reliability problems are provided. At the end of the study, the advantages and disadvantages of applying artificial neural networks to structural reliability problems are presented and compared with other known structural reliability methods. Additionally, a new convergence criterion and an adaptive algorithm have been developed. It was observed that applying artificial neural networks to structural reliability problems provides both efficient and accurate probability estimates.
Assessment of the 2018 Turkish seismic regulations unreinforced masonry construction specifications through a case study structure
(01. Izmir Institute of Technology, 2020-12) Turan, Egecan; Dönmez, Cemallettin; 01. Izmir Institute of Technology
The new release of the seismic regulation in 2018 resulted in major changes in masonry structures' design approach. It changes from the allowable stress design method to the ultimate strength design method. Also, the effect of vertical earthquake component, which was not considered, is included in the analysis combinations. The seismic risk is started to be defined by parameters determined according to the geographical coordinates of the building that is considered. The presented study is intended to investigate the impact of the listed changes on unreinforced masonry design. A case study building is utilized for this purpose. It is designed to satisfy the TER-2007 requirements and re-evaluated considering the TER-2018 requirements. The results show that the building did not have sufficient capacity, according to the 2018 earthquake regulation. Almost all the walls were beyond their capacities. The same structure has been analyzed by nonlinear static analysis (pushover analysis) as well. According to the nonlinear analysis results, performance assessment was made per the 2018 earthquake regulation and FEMA356. The performance evaluation by nonlinear static analysis using TER-2018 and FEMA356 demands, satisfies the life safety performance level for FEMA356 and TER-2018.
Behavior of reinforced concrete slabs subjeted to impact loads
(Izmir Institute of Technology, 2013) Batarlar, Baturay; Saatcı, Selçuk
This study presents the findings of an experimental program designed for investigating the behavior of RC slabs under low-velocity impact loads. Six RC slabs with dimensions 2015x2015x150 mm were tested at the Structural Laboratory of the Izmir Institute of Technology. To facilitate a comparison between the static and impact behavior of identical specimens, the slabs were cast in three identical pairs, such that one of the specimens was tested under impact loads whereas its identical twin was tested under static loads. To test the slabs under simply supported conditions, an innovative impact test setup was designed and manufactured, supporting the specimens at 20 locations along the perimeter and holding the specimens in place during the impact induced rebound. This setup was also used for the testing of the specimens under monotonically increasing static loads at the midpoint. Impact loads were induced on the specimens by a free falling drop-weight, impacting the specimens at the midpoint. The specimens were intensely instrumented with 20 load cells at each support location, 24 displacement transducers, 6 accelerometers and 12 strain gauges fixed to the reinforcing bars. Dynamic data was captured with the help of a high speed data acquisition system, capturing and recording the data at a rate of 250 kHz per channel. The results obtained from these tests revealed that the impact behavior of slabs differs significantly compared to their static behavior. Displacement profiles and force distributions are highly affected due to the high inertia forces during the impact.
A benefit/cost analysis for the seismic rehabilitation on existing reinforced concrete buildings in Izmir
(Izmir Institute of Technology, 2005) Boylu, Mert; Aktaş, Engin
The Aegean is one of the most seismically active regions of Turkey. The Eqarthquake disasters which occurred in Turkey recently, obligate the seismic rehabilitation of existing buildings and the new construction projects produced to require well-detailed seismic strengthing. On the other hand, before starting an expensive project such as seismic rehabilitation, a benefit/cost analysis is needed to determine whether the proposed project is economically feasible. In this study, a benefit/cost analysis model for the seismic rehabilitation of existing reinforced concrete buildings in Izmir is presented. To express the seismicity of Izmir City, between 1900-2003, the magnitude of Ms 4.9 earthquakes which occurred in Izmir and its vicinity are used as data. The Poisson Model is used to calculate the probability of occurrence. For the seismic risk of Izmir which includes damage to buildings and loss, various damage estimation methods are described. As a generalization of all of the existing reinforced concrete buildings in Izmir Region, two existing reinforced concrete buildings with total building area of 735 square meters and 716 square meters, respectively, which have different social functions, are chosen to estimate whether the seismic rehabilitations of the investigated buildings are economically justified. As a result of the analysis, benefit/cost ratios of both structures are found greater than one which means both rehabilitation projects are economically feasible.
A case study on settlement analysis of geothermal power plant foundation
(Izmir Institute of Technology, 2018-12) Elmas, Hakan; Ecemiş Zeren, Nurhan
Foundation settlement criteria are highly sensisitive for geothermal power plants. In geotechnical literature there are several settlement analyses which can be done by using elastic approaches, in-situ test results or numerical methods. Unfortunately, all these methods cannot give close results with each other. As a result, the unrepresentative analyses influence the safety, economy and time of the projects. In this study, the settlement of the geothermal power plant located in Aydın / İncirliova which constructed on a raft foundation was investigated. According to soil investigations, the raft foundation is located on multilayer soil profile and a compacted high qualified fill layer is placed under the raft foundation. Soil parameters were obtained from in-situ tests (standard penetration tests, cone penetration tests, pressuremeter tests and plate load test and) and laboratory experiments. Settlement results were obtained by 1D stress – strain analyses and 3D continuum numerical analyses (Hardening Soil Model with Small Strain Stiffness and Mohr Coulomb Soil Model) using the commercially available Settle 3D and Plaxis 3D software, respectively. The results of these analysis were also compared with the field monitoring data. The results show that Hardening Soil Model with Small Strain Stiffness gave more accurate result than other models due to the representation of real soil behavior, obtaining non-uniform stress distribution of foundation and obtaining effective stress depth accurately for settlement.
A case study: Site-specific seismic response analysis for base-isolated building in Düzce
(01. Izmir Institute of Technology, 2020-12) Eren, Volkan Gökçe; Ecemiş Zeren, Nurhan; 01. Izmir Institute of Technology
Under seismic loads, soil-structure interaction, and its effect on performance of pavements is more important today. Turkey is located in one of the most active seismic zones in the world. In the past, many destructive earthquakes happened in Turkey. The fact is that due to frequent earthquakes in the future, we may suffer a significant loss of life and property. Therefore, it has been necessary to minimize demolitions by conducting soil behavior analysis for each site. To design buildings, bridges, and other structures with base-isolators according to performance, it is necessary to carefully evaluate the long-term ground motions, especially in determining the earthquake ground motion. In these evaluations, empirical and theoretical methods to predict the response spectrum, considering and analyzing the effects of the near-fault, scaling the spectrum for different damping ratios, and simulation of long-term ground motions time-history constitute an essential place. It is necessary to determine the principles required for modifying the design spectrum in the long-period boundaries. The regulations are required to simulate long-period ground motions in the time-history and the necessary rules for selecting and scaling the earthquake ground motion records by considering the long-period effect. In this thesis, commonly used approaches in national and international regulations in defining the earthquake effect were evaluated, and the recommended earthquake levels for structures within the Düzce city in Turkey are explained. While evaluating the earthquake hazard in the study area, the general geology, tectonic features, ground conditions, and existing fault systems of the region were considered. For the study area, besides the classical hazard spectra, hazard curves for different spectral ordinates that allow the calculation of probabilistic seismic hazard maps and spectral coordinates for various periods are presented. Earthquake records were selected according to these spectra, and nonlinear analyses were made by simulating earthquake data for structural analysis. Turkey Earthquake Building Regulations (TBDY, 2018) to determine the seismic design spectrum is considered.
Categorization of web sites in Turkey with SVM
(Izmir Institute of Technology, 2004) Şimşek, Kadir; Püskülcü, Halis
In this study of topic .Categorization of Web Sites in Turkey with SVM. after a brief introduction to what the World Wide Web is and a more detailed description of text categorization and web site categorization concepts, categorization of web sites including all prerequisites for classification task takes part. As an information resource the web has an undeniable importance in human life. However the huge structure of the web and its uncontrolled growth led to new information retrieval research areas to be risen in last years. Web mining, the general name of these studies, investigates activities and structures on the web to automatically discover and gather meaningful information from the web documents. It consists of three subfields: .Web Structure Mining., .Web Content Mining. and .Web Usage Mining.. In this project, web content mining concept was applied on the web sites in Turkey during the categorization process. Support Vector Machine, a supervised learning method based on statistics and principle of structural risk minimization is used as the machine learning technique for web site categorization. This thesis is intended to draw a conclusion about web site distributions with respect to thematic categorization based on text. The popular web directory Yahoo.s 12 top level categories were used in this project. Beside of the main purpose, we gathered several statistical descriptive informations about web sites and contents used in html pages. Metatag usage percentages, html design structures and plug-in usage are some of these information. The processes taken through solution, start with employing a web downloader which downloads web page contents and other information such as frame content from each web site. Next, manipulating, parsing and simplifying the downloaded documents takes place. At this point, preperations for categorization task are completed. Then, by applying Support Vector Machine (SVM) package SVMLight developed by Thorsten Joachims, web sites are classified under given categories. The classification results obtained in the last section show that there are some over-lapping categories exist and accuracy and precision values are between 60-80. In addition to categorization results, we saw that almost 17 of web sites utilize html frames and 9367 web sites include metakeywords.
Characteristic properties and recyclability of aluminium beverage cans and coffee capsules
(Izmir Institute of Technology, 2022-06) Önen, Rabia; Genç, Aziz; Gökelma, Mertol
Recycling is an effective way to reduce environmental pollution. Recycled aluminium uses 95% less energy than primary production. Therefore, there is a high demand for more efficient recovery technologies. Aluminium is used in transportation, consumer products, and electronics. Short life cycles, thin walls, and surface coatings make aluminium recycling difficult. This study focuses on UBCs and coffee capsules' properties and recyclability (CCs). A lab-scale electrical resistance heating chamber furnace was used for the de-coating and remelting experiments. The coatings were characterized using Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS). As a result of the study, it was found that thermal pre-treatment temperature is more critical for alloys that have high Mg content due to their oxidation tendency. Suitable thermal pre-treatment temperature was observed between 520 to 550 °C for the samples. On the other hand, when the volatile organic content of the scraps was analyzed, it was observed that clean UBCs and CCs contain 2.2% and 9% volatile organic content, respectively, but it can be increased with increasing drink rest inside of it. A result of these experiments shows that the metal yield can differ up to 3.5% due to the drink residues (sugar). Also, it was observed that high-density pressing of the samples prior to the de-coating process increases the amount of the entrapped carbonaceous materials and decreases the de-coating efficiency. Finally, it was observed that samples with low wall thicknesses should be remelted under a salt flux to prevent oxidation and allow coalescence.
Comparatic-ve energy performance assesment of hemp-clay as building block material
(01. Izmir Institute of Technology, 2022-07) Ergün, Betül; Durmuş Arsan, Zeynep; Akkurt, Sedat
Bio-based and earthen building materials have recently started to be used again in seeking sustainable materials to combat climate change. Hemp-based building materials stand out as energy-efficient materials due to their favorable thermal properties, although they still have unstandardized features that vary by location. This study aims to investigate the thermal properties and energy performance of hemp-clay building blocks which are produced with local hemp and clay in the western Aegean region of Turkey for today and the future, leading up the research on hemp-based building materials in the Mediterranean region. The methodology of the research consists of laboratory experiments on material and building energy simulations via DesignBuilder software. Building block samples were produced with 27 different hemp-clay mixtures and tested using a quick thermal conductivity meter. Subsequently, the thermal performance of selected hemp-clay block was compared with conventional wall infill materials such as hollow clay brick, autoclaved aerated concrete, and lightweight pumice block via simulations of the annual energy consumption of an existing residential building in Izmir. Simulation scenarios were generated keeping wall thickness and U-value as constant for the climate of 2020, 2050, and 2080. Hemp-clay building blocks reduced the heating and cooling demands of the case building by 21% and 14%, respectively in 2020. Their energy performance outperformed the other materials' performances even if the scenario walls have the same U-value as hemp-clay walls in today's and the future's climate conditions. Consequently, the hemp-clay building blocks are apparent as a promising material to be improved in Turkey.
Construction and control of a desktop earthquake simulator
(Izmir Institute of Technology, 2006) Kınay, Gökçe; Turan, Gürsoy
A portable, servo motor driven, and single-degree-of freedom earthquake simulator is manufactured. The moving table has a dimension of 40 cm x 40 cm. It can carry a load of 80 kg, accelerated to 2 g (1 g @ 9.81 m/s 2 ). Its maximum displacement capacity is ± 7 cm. In order to obtain the desired motion, a voltage of .10 to +10 volts is applied to the servo unit (motor driver), which is adjusted to move the table at .25 cm/s and 25 cm/s, respectively. A runtime program is written to read an earthquake's velocity-time data and to produce an electrical voltage that takes care of the following two items: First, the maximum speed of the simulated earthquake can not be larger than the motor.s capacity. Second, the maximum earthquake displacement can not be larger than the table.s displacement capacity.In the present work, the recorded strong motion acceleration time series are processed in order to obtain useful data for engineering analysis. Strong motion accelerogram processing (earthquake data processing) is performed in Scilab. The objectives of strong motion data processing are corrections for the response of the strong motion instrument itself, and reduction of random noise in the recorded signals. The processing concentrates on the lowfrequency ranges of the usable signal in the records.The results obtained from comparison of the present work's outputs and some data providers' outputs are satisfactory. Some slight differences exist due to the different integration schemes and due to the application of different filter orders, zero-padding, and different filters for instance, acausal or causal Butterworth filter.The simulations are performed in a regular Linux environment and also in a Realtime Linux environment. The advantage of the realtime environment ensures the signals send to the servo driver to be on-time . no delay due to operating system tasks.
Crystal plasticity inspired modelling of fibre reinforced composites
(Izmir Institute of Technology, 2022-07) Dizman, Emir Aybars; Özdemir, İzzet
There is an increasing demand in carbon fibre reinforced (CFR) composites primarily due to their high strength-to-weight ratio. Although their single-ply behaviour is rather brittle (as compared to metals), by reducing the ply thickness and stacking differently oriented plies, brittleness is suppressed, and a ductile behaviour similar to metals is achieved. In this thesis, a recently proposed material model inspired by crystal plasticity is reconsidered and implemented in an implicit finite element solution framework. To this end, a user-defined element is developed in a geometrically non-linear continuum setting and implemented in commercial finite element software Abaqus through UEL (Userdefined ELement) subroutine. The model is validated by analytical solutions derived for simple shear cases and two experiments for different loading cases from the literature. The model is capable of predicting stress-strain response well in cases where matrix plasticity is dominant. Moreover, a parametric study on the cross-ply shear specimen is conducted to investigate the influence of different material parameters. In the last part, the model is extended by a continuum scale damage in the matrix and degradation in elastic material properties. The predictive capabilities of the damage extended model are assessed by re-analyzing the cross-ply shear test.
Design of Coanda intakes for optimum sediment release efficiencies and water capture performances
(Izmir Institute of Technology, 2020-05) Hazar, Oğuz; Tayfur, Gökmen; Elçi, Şebnem
Bottom type water intake structures are frequently preferred in the case of flows containing high levels of sediment in case where it is not possible to construct settling pool or if their construction costs are high. Coanda and Tyrolean type water intake structures are the most commonly used bottom type intake structures. It has been observed in a limited number of studies that Coanda type water intakes are superior to the Tyrolean type water intakes both in terms of withdrawing the design amount of flow and excluding the sediment as much as possible. However, the biggest obstacle to the widespread usage of Coanda type water intake is their complex design and difficulties of the analysis. It has been observed that there are no formula or numerical studies that calculate the water Capture Performance (WCP) and Sediment Release Efficiency (SRE) of the Coanda screens. In order to overcome this gap in the literature, six different Coanda screens have been tested for both WCP and SRE using various incoming flows and sediment compositions. The data obtained as a result of the experimental studies were analyzed using statistical analysis method and two different equations were obtained that enable to find the WCP and SRE. In a situation where the incoming flow conditions and screen parameters are known, someone can gain a preliminary knowledge about the screen performance by using these equations. As a result of this study, adding new data to the literature and eliminating the mentioned lack in the literature was aimed.
Develepment of a new test method to evaluate dynamic stability of self-consolidating concrete
(Izmir Institute of Technology, 2014-07) Alami, Mohammad Musa; Erdem, Tahir Kemal
Self-consolidating concrete (SCC) is a new generation of concrete with high performance. It is able to flow under its own weight and fills the formwork without any external vibration. Stability is the most important plastic and crucial property for successful application of SCC and it refers to segregation of constituent in fresh state. Dynamic stability is the segregation resistance of SCC during transportation and placement. Evaluation of dynamic stability is one of the most investigated topics of SCC. Many different test methods have been proposed to evaluate the dynamic stability of SCC. No single and widely accepted method exists for the evaluation of the dynamic stability of SCC. In this thesis a new apparatus for testing the dynamic stability of SCC was developed. The effect of different mix design parameters such as water-to-cement ratio w/c, slump flow diameter, coarse aggregate-to-total aggregate ratio (CA/TA), and maximum size of aggregate (Dmax) were evaluated on the dynamic stability of SCC. Several fresh concrete tests were carried out on the SCC mixtures: slump flow, T500 time, Visual stability index (VSI), V-funnel, L-box, static sieve segregation (GTM), rheometer, and new proposed method (DSST). Several correlations were established between the test results. It was found that the new proposed test is a suitable method to evaluate the dynamic stability of SCC. Limits were proposed for a dynamically stable SCC.
Discrete element modelling of CPT using shaking table tests in sands
(Izmir Institute of Technology, 2014-07) Bakunowicz, Paulina; Ecemiş, Nurhan
This thesis contains an overview of the results obtained from detailed study exploring the ability of two-dimensional discrete element method (2D DEM) models to reproduce cone penetration tests in saturated sand deposits. The simulations of the cone penetration and triaxial tests are carried out under application of the commercially available numerical analysis software PFC2D (Itasca, 2008). This software is based on DEM with additional basic fluid analysis option. The soil sample used in the laboratory experiments was uniform, river clean quartz sand, which was similar to Ottawa sand. The material properties that required calibration were normal stiffness, tangential stiffness and interparticle friction. These parameters were determined by trial and error from 2D DEM biaxial test simulations. Data from five laminar box shaking table tests of saturated sand was analysed with particular attention to the measured cone penetration resistance in assemblages deposited at various relative densities. Each shake table test was subjected to three series of shaking tests (at the same intensities) by using one-degree of freedom shaking table system, which allowed obtaining wide scope of different porosities. A new scaling factor was implemented in order to compare the data obtained from tests on real soil (3D) with numerical simulations by DEM (2D). Observations of the behaviour of discrete material at laminar box enabled us to make a correlation between porosity from large scale experiment and PFC2D model. To examine the effects of boundary conditions, porosity, particle diameter size, fluid grid dimensions, contacts, coordination number and others on the tip resistance value, multiple simulation tests were performed. From the results presented we can deduce that 2D DEM CPT model can be powerful tool to enrich the conventional physical calibration tests. In this thesis it is also proven that CPT laminar box based correlations facilitate to overcome limitations of 2D simulation and can be widely and successfully applied for both scientific research and engineering practice purposes.
Drought and trend analysis in Trarza region im Mauritania
(Izmir Institute of Technology, 2016-07) Traore, Ely Yacoub; Tayfur, Gökmen
Long-term precipitation and temperature historical records (monthly recorded for 44 years) in three stations (Boutilimit (station 1), Nouakchott (station 2), and Rosso (station 3)) are employed to investigate the drought characteristics and to investigate the temperature and precipitation trends during the period of 1970 to 2013 in Trarza region in Mauritania. Six Drought Indices (DIs), namely normal Standardized Precipitation Index (normal-SPI), log normal Standardized Precipitation Index (log-SPI), Standardized Precipitation Index using Gamma distribution (Gamma-SPI), Percent of Normal (PN), the China-Z index (CZI), and Deciles are used for the drought analysis. These methods are based on 1-, 3-, 6-, and 12 month time periods. The results showed that the log-SPI, the gamma-SPI, PN and Deciles were able to capture the historical extreme and severe droughts observed in early 1970s and early 1980s. In the trend analysis, The Mann Kendall (MK test), Spearman’s rho (SR test), Şen trend test were used for the trend identification in the time series and the Pettitt test for detecting the change point at the time series while the Thiel-sen Approach was used to estimate the magnitude of the slope in the precipitation and temperature time series. The results of trend analysis showed that the average temperature and the annual precipitation are both increasing by about 0.3oC per decade and 3 mm per year, respectively.
Drought assessment in Aydın and İzmir Districts in Turkey
(01. Izmir Institute of Technology, 2022-11) Mersin, Denizhan; Safari, Mir Jafar Sadegh; Tayfur, Gökmen
Drought indices are widely used in order to track the severity, duration, and frequency of droughts, drought indices are frequently utilized. Turkey's Aegean region, which is expanding, has a range of water resources, including lakes, streams, lakes, and groundwater aquifers. In this study, the drought features in the Büyük Menderes, Küçük Menderes, and Gediz basins in the Aegean area of Turkey are investigated using long-term total precipitation and temperature records from 14 meteorological stations between 1973 and 2020 (47 years). For this, the Standardized Precipitation Index (SPI) and the Standardized Precipitation and Evapotranspiration Index (SPEI), and Discrepancy Precipitation Index (DPI) are used to investigate drought patterns, monthly and over 3-, 6-, and 12-month (annual) periods. The results reveal that the monthly indices show almost the same results for the whole study area, but the different indices differ in the severity of drought. As a common belief, moderate, severe, and extreme drought is observed at the end of the 1980s and around 2020, which is the closest year to the present. In addition, the trend analysis of the annual temperature (daily average) and total precipitation time series data collected from these 14 stations is examined. Sen test, Mann-Kendall test, and Spearman's rho test are used for trend detection. The Pettitt test is used to estimate the magnitude of the slope in the series and the Theil-Sen approach is used to detect the change point of the series. For precipitation, all stations showed a statistically significant increase in trends. In the temperature analysis, on the other hand, all stations show statistically significant increasing trends in daily average temperatures. The amount of precipitation increase determined by the Theil-Sen test is found to be between 4.2 and 7.9 mm/year.
Dynamic behavior of reinfor ced concrete frames with infill walls
(Izmir Institute of Technology, 2011) Çankaya, Mehmet Alper; Dönmez, Cemalettin
Current practices utilize infill walls as insulation or partition material but not as a structural material. The main reason for this choice is the complexity of the partition wall-frame interaction behavior. Therefore infill walls typically ignored in the structural designs. However, existence of partition walls heavily effect stiffness, strength and behavior of structures. The main purpose of the presented study is the investigation of the dynamic parameters of reinforced concrete frames with and without infill walls. Moreover, lateral strength, stiffness and energy dissipation properties of the frames are also studied. In order to achieve the purpose four planar, one-bay, four story RC frames with 1/5 scale are designed, constructed and tested. In the frames main parameters are selected as presence of partition walls and ductile/non-ductile reinforcement detailing. Experiments are consisted of static and dynamic tests. In static tests each frame subjected to lateral loads that were applied at the each story level to provide a lateral loading increasing with height. Lateral load levels were controlled by the drift levels in the first story. Dynamic tests were performed at the end of each deformation level and modal analysis methods are utilized. Analyses have shown that existence of partition walls in the frame increased the natural frequencies of the frames. However, reinforcement detailing did not have a significant effect on natural frequencies. It is also observed that the natural frequencies of the frames decreased with increasing damage level. On the other hand, presence of partition walls effected the damaged behavior of the frames and drift is observed to concentrate to the first story with the increasing level of damage. And finally stiffness, strength and energy dissipation properties of frames with partition walls are observed to be dramatically higher than the frames without partition walls.
Earthquake response of R/C frames with reinforced infill walls
(Izmir Institute of Technology, 2008) Yıldırım, Umut; Turan, Gürsoy
Most of the reinforced concrete structures that are built in the past few decades are in lack of ductility and lateral stiffness. In the content of the present work, a fast and economical remedy was searched to rehabilitate these type of buildings that are under high risk of earthquake damage.The strengthening technique needs to be finished in a short time without the people that live inside the buildings to move out. Furthermore, the chosen strengthening technique needs to be economical enough so that the home owner would not hesitate in making a decision of the rehabilitation.In regard of the above mentioned two criteria, existing infill clay brick walls may be strengthened by the addition of a wire mesh on the surface together with a layer of plaster. In order to investigate its effectiveness, a numerical investigation is carried out to study the behaviour of a strengthened infilled reinforced concrete (RC) frame using wire mesh under lateral reversed cyclic loading. A single span, one-story clay brick infilled RC frame is modeled and a nonlinear analysis is made.The analysis results indicate that the technique of strengthening with wire meshincreased the peak lateral load, ductility and energy dissipation.

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