İnşaat Mühendisliği Bölümü Yayın Koleksiyonu

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https://hdl.handle.net/20.500.12885/1681

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Moving-load dynamic analysis of AFG beams under thermal effect
(Techno-Press, 2022) Akbaş, Şeref Doǧuşcan
In presented paper, moving load problem of simply supported axially functionally graded (AFG) beam is investigated under temperature rising based on the first shear beam theory. The material properties of beam vary along the axial direction. Material properties of the beam are considered as temperature-dependent. The governing equations of problem are derived by using the Lagrange procedure. In the solution of the problem the Ritz method is used and algebraic polynomials are used with the trivial functions for the Ritz method. In the solution of the moving load problem, the Newmark average acceleration method is used in the time history. In the numerical examples, the effects of material graduation, temperature rising and velocity of moving load on the dynamic responses of AFG beam are presented and discussed.
Buckling Analysis of a Fiber Reinforced Laminated Composite Plate with Porosity
(UNIV TEHRAN, 2019) Yüksel, Yusuf Ziya; Akbaş, Şeref Doǧuşcan
Fiber-reinforced laminated composites are frequently preferred in many engineering projects. With the development in production technology, the using of the fiber reinforced laminated composites has been increasing in engineering applications. In the production stage of the fiber-reinforced laminated composites, porosities could be occurred due to production or technical errors. After a level of the porosity, the mechanical behaviors of composite materials change significantly. This paper presents buckling analysis of fiber-reinforced laminated composite plate with porosity effects within the first shear deformation plate theory. In the porosity effect, three different porosity models are used in the laminated composite plate. The material properties of the laminas are considered as orthotropic property. In the solution of the problem, the Navier procedure is used for the simply supported plate. Influences of the porosity coefficients, the porosity models, the fiber orientation angles and the sequence of laminas on the critical buckling loads are presented and discussed.
Effect of high temperature on polypropylene fiber-reinforced mortars containing colemanite wastes
(Elsevier, 2021) Durgun, Muhammed Yasin; Özen, Süleyman; Karakuzu, Kemal; Kobya, Veysel; Bayqra, Sultan Husein; Mardani-Aghabaglou, Ali
In this study, the effect of polypropylene (PP) fiber utilization ratio on the fresh and some hardened properties of mortar mixtures containing colemanite waste (CW), which mainly contains B2O3, SiO2 and CaO, containing mortar mixtures were investigated. The 17 mortar mixtures were prepared by replacing 0, 1, 3, 5, and 7 wt% of cement with CW and by adding 0, 0.5, 0.75, and 1% by volume of PP fibers to the control mixture. In all mixtures, water/binder ratio, sand/binder ratio and slump-flow values were kept constant as 0.485, 2.75 and 220 +/- 20 mm, respectively. Water reducing admixture requirement of each mixture was determined to provide the target slump-flow range in mortar mixtures. There was a change in the amount of admixture according to the amount of CW and fiber content in the mixture. The 28 and 56-day water absorption capacity, compressive strength and high temperature resistance of mortar mixtures were determined. Strength reduction of specimens exposed to 300 degrees C and 600 degrees C were compared. In addition, thermal and scanning electron microscopy (SEM) analyses were performed on the specimens. According to the test results, with the increase in the amount CW and PP fiber in the mixtures, the admixture demand to provide target flow value and the 28-day water absorption capacity of the mixtures increased, while the 28-day compressive strengths decreased. However, while there was no significant change in the 56-day water absorption capacity and compressive strength values of the specimens containing CW, the water absorption capacity increased and the compressive strength decreased upon the presence of fiber in the matrix. The specimens containing both of CW and PP fiber showed better performance in terms of high-temperature resistance.
Sodium silicate-formamide grouted silt and silty sand properties
(2021) Avcı, Eyübhan
In this study, the hydraulic conductivity and strength characteristics of various graded silt and silty fine sands grouted with sodium silicate-formamide solutions were investigated. In the determination of the most suitable sodium silicate-formamide solutions for grouting, viscosity, gel time, and syneresis tests were implemented at first. SF1 and SF7 solutions were found convenient accordingly. The groutability tests were conducted on the silt and silty fine sand specimens prepared at five different gradations with SF1 and SF7 solutions and all specimens were successfully grouted. The successfully grouted specimens were kept under two different curing conditions, wet-cured and air-dried, and subjected to unconfined compressive strength (UCS) tests at different time intervals. As the UCS of air-dried specimens increased the UCS of wet-cured specimens decreased with time. In general, the UCS of air-dried specimens was higher than those of wet-cured samples. The UCS values of specimens grouted with SF1 solutions were higher than those of SF7 grouted specimens. On the other hand, the permeabilities of silt and silty fine specimens were reduced with both SF1 and SF2 grouts and the permeabilities of SF1 injected samples were higher than those of SF7 grouted samples. The permeabilities of SF1 and SF7 grouted specimens increased with time.
Regressive-stochastic models for predicting water level in Lake Urmia
(Taylor and Francis Ltd., 2021) Vaheddoost, Babak; Aksoy, Hafzullah
This study develops a set of models to investigate the water budget of Lake Urmia in Iran, a permanent hypersaline lake that has suffered a declining water level since the late 1990s. The models are of the regressive-stochastic type, a combination of multilinear regression and autoregressive integrated moving average stochastic models. The multilinear regression models were used to construct the core of the relationship of lake water level to streamflow, precipitation, evaporation and groundwater depth. Afterward, stochastic models were used to generate data for each independent variable to estimate the oscillation in the lake water depth. Several criteria were used to compare the performance of the models in the aggregated and disaggregated cases with which the pre- and post-encroachment periods are considered, respectively. The regressive-stochastic models are found to be competitive with the existing models developed so far for Lake Urmia water level.
Hygrothermal stress analysis of laminated composite porous plates
(Techno-Press, 2021) Yüksel, Yusuf Ziya; Akbaş, Şeref Doǧuşcan
This paper presents the stress analysis of a composite laminated simply supported plate with porosity under hygrothermal rising. In the displacement-strain relation of the plate structure, the first shear plate deformation theory is used. Material properties of laminas are considered as orthotropic. Three different porosity distributions are used. In the solution process, the Navier method is implemented for simply supported laminated composite plate. Non-uniform temperature and moisture rising are considered for laminated plate with three laminas. In the numerical results, the stress distributions of the laminated plate are presented and discussed for different values of moisture, temperature, stacking sequence of laminas and orientation angle of layers. The numerical results show that the hygrothermal condition is very effective in the stress behavior of laminated plates.
Gender equality on developing transport system in sicily: A consideration on regional scale
(American Institute of Physics Inc., 2021) Campisi T.; Nahiduzzaman Kh.Md.; Akgün, Nurten; Ticali D.; Tesoriere G.
The development of transport technologies and systems, taking into account individual and/or shared mobility systems, should involve not only the characteristics of the places where it develops, but also the characteristics of road users. The increase in transport supply makes it easier to achieve job opportunities and thus increases the potential for wealth. The development of different forms of mobility also offers better access to areas, such as education centers, and limits the disparity between road users of different age groups and gender. The presence of children and income characteristics are factors that can influence women's mobility choice such as using public transport, owned/shared micro mobility, or e-bikes. The study in this paper defines in a first phase some considerations on gender equality through describing some case studies from the South of the world. A questionnaire, including 1150 women over 18 years old in the use of the different modes of transport in the region of Sicily in southern Italy, was carried out. The results highlight the critical issues that often lead to different perceptions of safety on board or gender equality considering both the passenger's and the driver's point of view. The limits of the research are related to the analyzed sample. The work shows a first step of investigation aimed at future research actions to reduce gender inequalities, providing the basis for the definition of ad hoc strategies by local authorities and dedicated vouchers or fares by operators of transport services for women.
Effect of Sodium Silicate on the Strength and Permeability Properties of Ultrafine Cement Grouted Sands
(American Society of Civil Engineers (ASCE), 2021) Avcı, Eyübhan; Deveci, Emre; Gokce A.
In this experimental study, the effect of sodium silicate (SS) added into an ultrafine-cement-suspension injection on the strength and permeability properties of grouted sand samples was investigated. The experiment started with a test for identifying the bleeding and viscosity values and setting times. This was followed by injecting sand samples prepared in different gradations with ultrafine cement (UC) with and without SS additive. In the experiments, 1.0, 1.5, 2.0, and 2.5 were used as the water:cement ratios, and 1%, 3%, and 5% were used as the SS additive ratios. Unconfined compression tests were performed on the sand specimens that were successful in the injection tests on days 3, 7, 14, 28, 56, and 90; and permeability tests were performed on days 7, 28, 56, and 90. While viscosity values increased with the addition of SS into the UC, bleeding values and setting times decreased. Injectability slightly decreased with the addition of SS into the UC. The addition of SS into the UC-suspension injection increased the unconfined compressive strength. Injected samples gained strength faster with the addition of SS into the UC. Adding sodium silicate into the UC-suspension injection reduced permeability values. In the experimental study, it was observed that the addition of SS additive into the UC improved the permeability and strength properties of sand samples after injection.
Multi-effect of superplasticisers main and side-chain length on cementitious systems with fly ash
(ICE Publishing, 2022) Özen, Süleyman; Altun M.G.; Mardani-Aghabaglou A.; Ramyar K.
In this study, the effect of main chain and side chain length of polycarboxylate-ether based high range water reducing admixture (WRA) on the fresh properties, compressive strength and water absorption of cementitious systems containing 0, 15, 30 and 45 wt.% fly ash was investigated. For this purpose, 3 WRAs with same molecular weight but different chain lengths were produced. According to test results, flowability of paste and mortars was negatively affected when the length of the main chain and side chains of the admixture was longer or shorter than a certain value. This adverse effect is thought to be arisen from the weakening of the adsorption of admixture with increase of its chain lengths. However, when the main chain and side chain lengths of the admixture were shorter or longer than a certain value, the time-dependent flow properties of the mortar mixtures improved. The main chain and side chain lengths of the WRAs had not a significant effect on the compressive strength and water absorption capacity of the mortar mixtures. However, irrespective of the admixture characteristics, with the increase of fly ash substitution the flow and time-dependent flow properties of the mixtures were negatively affected but their water absorption decreased.
Dynamic Analysis of Functionally Graded Porous Microbeams under Moving Load
(Springer Science and Business Media B.V., 2021) Akbaş, Şeref Doǧuşcan; Dastjerdi S.; Akgöz B.; Civalek Ö.
This paper presents dynamic analysis of a simply supported porous microbeam made of functionally graded materials subjected to a moving load. Material properties of the porous microbeam change in the thickness direction according to power-law distribution with different porosity models. The governing equations are obtained by Lagrange procedure based on Bernoulli–Euler beam and modified couple stress theories. Then, the resulting equations are solved by Ritz and Newmark average acceleration methods. A detailed parametric study is performed to investigate the effects of porosity coefficient, porosity distribution, material distribution, and length scale parameter on the dynamic responses of functionally graded porous microbeams.
Dynamic analysis of axially functionally graded porous beams under a moving load
(2021) Akbaş, Şeref Doǧuşcan
In presented paper, moving load problem of functionally graded beams is investigated with porosity effects based on the first shear beam theory. The material properties of beam vary along the axial direction. The porosity is depicted by two different distributions along axial direction. The governing equations of problem are derived by using the Lagrange procedure. In the solution of the problem the Ritz method is used and algebraic polynomials are used with the trivial functions for the Ritz method. In the solution of the moving load problem, the Newmark average acceleration method is used in the time history. In the numerical examples, the effects of material graduation, porosity distribution, porosity coefficients and velocity of moving load on the dynamic responses of axially functionally graded beam are presented and discussed. The dynamic responses are obtained for different boundary conditions.
Engineering properties of ultrafine blast furnace slag cement stabilized low plasticity clayey soil
(Gazi Universitesi, 2021) Mollamahmutoǧlu M.; Avcı, Eyübhan; Deveci, Emre; Gökçe A.
In this study, it was aimed to determine some engineering properties of the low plasticity clayey soil stabilized with ultrafine blast furnace slag cement (Spinor A6). Firstly, the fundamental geotechnical characteristics of clayey soil specimens stabilized with the contents of 8%, 10% and 12% ultrafine blast furnace slag cement were experimentally ascertained. Then, the compressive strength, compressibiliy and swelling tests were conducted on the ultrafine blast furnace slag cement stabilized clayey soil specimens that were compacted at the optimum moisture content and maximum dry density. Experimental data showed that after stabilization of low plasticity clayey soil with ultrafine blast furnace slag cement, its strength increased by 9 to 14 times in air dried samples and 9 to 12 times wet-cured samples after 90 days. In addition, at the end of the 90th day, compressibility decreased between 18.3 and 19.2 times in air dried samples and between 17.6 and 18.5 times in wet-cured samples. Finally, it was determined that the swelling potential decreased between 67.5 and 270.0 times in the samples that were kept in the air dried at the end of the 90th day and between 54.0 and 101.2 times in the samples that were kept in the wet-cured samples. Test results showed that the compressive strength of low plasticity clayey soil increased and its compressibility and swelling index decreased with time as ultrafine blast furnace slag cement was added to the soil.
Effects of reinforcement corrosion on reinforced concrete buildings
(ICE Publishing, 2021) Yüksel, İsa; Sakcalı, Gökhan Barış
The aim of this paper is to present the different effects of reinforcement corrosion on reinforced concrete buildings. A hypothetical five-storey reinforced concrete building frame was designed for this purpose. Three different modes of action were selected - corrosion on the ground floor alone, corrosion on one facade and corrosion on two neighbouring facades of the building. For each mode of action, different corrosion scenarios were selected, which were arranged in terms of mass loss from zero to 15% in ascending order an in 3% steps. Pushover analyses of the building were performed for each corrosion scenario and the results of these analyses were used to perform a structural performance evaluation conforming to Eurocode 8. A general decrease in structural performance was determined with significant changes in the dynamic characteristics of the building. The level of decrease depended on the corrosion scenarios and the modes of action. Important structural behaviour alterations and premature damage occurrences were found, in addition to a reduction in the displacement ductility of the building. For severe-corrosion scenarios, reductions in moment and curvature capacities could shift the structural behaviour of the load-bearing members from ductile to non-ductile.
Effects of material properties on the mechanical and durability behaviors of Khorasan mortar mixtures: a review
(Taylor and Francis Ltd., 2021) İsafça T.; Karakuzu K.; Özen, Süleyman; Doğangün A.; Mardani-Aghabaglou A.
Historical buildings are an important piece of our cultural heritage. It is important that the materials used in the preservation, repair and reinforcement applications of these structures should be compatible with the existing structure. In many of the historical buildings in Turkey, it was reported use of the Khorasan mortar as the masonry mortar and plaster. Khorasan mortar contains slaked lime as a binder, river sand, and clayey materials as aggregate, which are fired at high temperature. It was emphasized that this mortar is an essential building material widely used in the construction and repair of historical buildings from past to present. In this study, the effects of binder, aggregate, chemical admixture, organic admixture, and fiber properties on the mechanical and durability performance of Khorasan mortar and lime-based mortar mixtures were investigated. For this purpose, a comprehensive literature research was carried out on this subject. In addition, the positive and negative effects of these materials on the mortar mixture were emphasized.
Damped forced vibration analysis of layered functionally graded thick beams with porosity
(Techno-Press, 2021) Alnujaie A.; Akbaş, Şeref Doǧuşcan; Eltaher M.A.; Assie A.E.
The following article presents the damped forced vibration of layered functionally graded thick beams including material porosities. In case of very thick beams, beam theories fail to satisfy boundary conditions and to predict the mechanical response accurately. So, the two-dimensional (2D) plane continuum model is exploited to model a thick functionally graded layered beam. The beam is composed from three- layers with functionally graded porous materials. The porosity is described by three different distribution models through the layer thickness. Applied forces to the functionally graded beam are assumed to be sinusoidal harmonic point load in time domain. The Kelvin-Voigt viscoelastic constitutive model is used to simulate damping effect. The governing equations are obtained by using Lagrange's equations. In frame of finite element analysis, twelve -node 2D plane element is exploited to discretize the space domain of thick beam. In the solution of the dynamic problem, the Newmark average acceleration method is used. Numerical studies illustrate effects of porosity distribution, stacking sequence, and graduation constant on the dynamic responses of layered functionally graded porous thick beams. The results show that the porosity function, stacking sequences and the damping ratio have a vital role in dynamic response of functionally graded beams. The proposed model can be used in nuclear, marine, and aerospace technologies.
Discharge coefficient for vertical sluice gate under submerged condition using contraction and energy loss coefficients
(Elsevier Ltd, 2021) Vaheddoost, Babak; Safari M.J.S.; Ilkhanipour Zeynali R.
A novel method is suggested for the determination of flow discharge in vertical sluice gates with considerably small bias. First, in order to derive an equation for the discharge coefficient, energy-momentum equations are implemented to define the physical realization of the phenomenon. Afterward, the discharge coefficient is presented in terms of contraction and energy loss coefficients. Subsequently, discharge coefficient, contraction, and energy loss coefficients were determined through an implicit optimization technique on the data. Data analysis illustrated that there is a meaningful power relationship between the contraction and energy loss coefficients. Thereafter, dimensional analysis is performed and an explicit best-fit regression equation is developed for defining the energy loss coefficient. The obtained equations for contraction and energy loss coefficients were then used in the computation of the discharge coefficient and determination of the flow discharge in the vertical sluice gate. The performance of the developed approach is validated against the selected benchmarks existing in the literature.
Dynamic analysis of a fiber-reinforced composite beam under a moving load by the ritz method
(MDPI AG, 2021) Akbaş, Şeref Doǧuşcan; Ersoy H.; Akgöz B.; Civalek Ö.
This paper presents the dynamic responses of a fiber-reinforced composite beam under a moving load. The Timoshenko beam theory was employed to analyze the kinematics of the composite beam. The constitutive equations for motion were obtained by utilizing the Lagrange procedure. The Ritz method with polynomial functions was employed to solve the resulting equations in conjunction with the Newmark average acceleration method (NAAM). The influence of fiber orientation angle, volume fraction, and velocity of the moving load on the dynamic responses of the fiber-reinforced nonhomogeneous beam is presented and discussed.
Conceptualization of the indirect link between climate variability and lake water level using conditional heteroscedasticity
(Taylor and Francis Ltd., 2021) Fathian F.; Vaheddoost, Babak
This study investigates the indirect effect of large-scale climate oscillations and the corresponding teleconnection with lake water level (WL) oscillations. For this, the effect of the Southern Oscillation Index (SOI), and North Atlantic Oscillation (NAO) on the Lake Urmia WL during 1966–2016 is investigated using cross-correlation, cross-wavelet (XWT), wavelet-coherence (CWT), and nonlinear multivariate generalized autoregressive conditional heteroscedasticity (GARCH) models. Based on the XWT and CWT analyses, a temporal phase of WL leading by the SOI and an anti-phase of WL-NAO linkage within 11 years is evident. The models also depict a long-term persistence and effectiveness of the conditional covariance on both SOI–WL and NAO–WL links. It is concluded that the SOI and NAO have no immediate impact on the WL while the magnitude of the impact is exacerbated after the year 2000; however, the establishment of the SOI–WL link is found to be more relevant than that of the NAO–WL link.
Application of Signal Processing in Tracking Meteorological Drought in a Mountainous Region
(Birkhauser, 2021) Vaheddoost, Babak; Safari M.J.S.
This study addresses the application of signal processing in the evaluation of meteorological drought associated with monthly precipitation time series. Several drought indices and a Haar wavelet decomposition (WD) with ten components are implemented in the evaluation of the monthly precipitation of a mountainous region called Mount Uludag in Turkey. Monthly precipitation time series in three meteorological stations at the summit and foothills are used. The Standardized Precipitation Index (SPI) is used at monthly, annual, and 12- and 48-month moving average time frames as the benchmark to investigate the drought patterns. The results obtained by the WD and SPI are then confirmed using the Z-score index (ZSI) at monthly and annual scales, together with the modified China Z-index (MCZI) and rainfall anomaly index (RAI) at a monthly scale. Changes in the moments of the distribution, correlation analysis, mutual information, and power spectrum are applied to investigate the nature of the relationship between the sequences of precipitation events in time and space. The temporal correlation analysis, together with the mutual information, showed that the system has a short-term memory with strong seasonality. Similarly, the power spectra depicted major seasonality at 1, 3, 5, 6, 12, 22, and 60 months in the precipitation time series. It is concluded that the recent drought events have an infrequent nature, which altered the sinusoidal patterns of the large-scale events. The SPI-48 and the WD showed that declines are strongly related to the large-scale cycles, but the decline patterns are more related to the station located at the mountain summit.
Forced vibration analysis of a fiber reinforced composite beam
(Techno-Press, 2021) Akbaş, Şeref Doǧuşcan
In this study, forced vibration analysis of a fiber reinforced composite cantilever beam is investigated under a harmonic load. In the beam model, the Timoshenko beam theory is used. The governing equations of problem are derived by using the Lagrange procedure. In the solution of the problem the Ritz method is used and algebraic polynomials are used with the trivial functions for the Ritz method. In the solution of the forced vibration problem, the Newmark average acceleration method is used in the time history. In the numerical examples, the effects of fibre orientation angles, the volume fraction and dynamic parameters on the forced vibration response of fiber reinforced composite beam are presented and discussed.

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