İşbuğa, Volkan
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İşbuğa, V
Isbuga, V
Isbuga, V.
Işbuǧa, V
Işbuǧa, V.
İşbuğa, V.
Isbuga, Volkan
Işbuǧa, Volkan
Isbuga, V
Isbuga, V.
Işbuǧa, V
Işbuǧa, V.
İşbuğa, V.
Isbuga, Volkan
Işbuǧa, Volkan
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volkanisbuga@iyte.edu.tr
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03.03. Department of Civil Engineering
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Current Staff
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Documents
9
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91
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5
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4
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40
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9
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4
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4
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40
Scopus Citation Count
45
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4.44
Scopus Citations per Publication
5.00
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4
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4
| Journal | Count |
|---|---|
| Computers and Geotechnics | 2 |
| Arabian Journal for Science and Engineering | 1 |
| Arabian Journal of Geosciences | 1 |
| Quarterly Journal of Engineering Geology and Hydrogeology | 1 |
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9 results
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Now showing 1 - 9 of 9
Master Thesis The Modified Vlasov Foundation on Nonlinear Soil Layers(01. Izmir Institute of Technology, 2021) Çerezci, Mehmet; Çerezci, Mehmet; İşbuğa, Volkan; İşbuğa, VolkanIn this thesis, a novel approach to account for the soil nonlinearity of nonhomogeneous soil deposits by employing the modified Vlasov foundation model is developed. A new algorithm that takes the modulus degradation curves at varying strain levels into account in an iterative manner is obtained by modifying the previously developed formulation. The presented model will provide researchers with the opportunity to employ the experimental test data directly for an operational strain level that may occur in many foundation engineering designs. This new model which takes the nonlinear soil behavior into account is first verified against the linear model given in the literature to ensure that the new model algorithm can capture the linear solution when the soil behavior is assumed to be linear. Later, the experimental data of modulus reduction curves reported in the literature for a specific type of dense and loose sands are used in multiple foundation deflection analyses. Example problems are considered for different cases which presented: (i) how the model captures nonlinear behavior and (ii) the significant effect of the nonlinear soil behavior on deflection, moment, and shear force. The model results are also compared with the finite element model result, assuming a bilinear stress-strain soil model. The results obtained from both models matched well, especially for the maximum deflection values that occurred in the example problems.Letter Reply To the Discussion on “the Modified Vlasov Model on a Nonhomogeneous and Nonlinear Soil Layer”(Elsevier, 2023) İşbuğa, Volkan; Çerezci, Mehmet; Aşık, A. ZülfüThe discussion suggests that the paper has left out four references (Haldar and Basu, 2013; Haldar and Basu, 2016; Elhuni and Basu, 2019; Elhuni and Basu, 2021), and the research work in the paper is not new. The authors would like to state that the literature review in the paper was kept as vast as and to stay as close as possible to the model given in the paper, which is a gross model. The study aimed to offer a method using a previously developed formulation for accounting for soil nonlinearity (Vallabhan and Das, 1988,1991a,1991b). The primary concentration in the literature was given to the most relevant works on the modified Vlasov model that employs the same concept for the solution method and algorithm, which lays the foundation of the paper (Vallabhan and Das 1988,1991a,1991b; Asik, 1999; Asik and Vallabhan,2001). On the other hand, as clearly indicated in the study, the literature in the field is extensive, including the works suggested by the discussion. Despite the author’s efforts, it was not possible to review or/ and mention all the works previously conducted to solve the problem with different approaches. In this respect, the previous studies by Haldar and Basu (2013) and Elhuni and Basu (2019) mentioned in the discussion are not directly related to the problem considered in the paper. Haldar and Basu (2016) proposed a framework incorporating the finite difference and the finite element methods.Article Citation - WoS: 9Citation - Scopus: 11Modeling of Pile-Soil Interaction in Laterally Loaded Pile Groups Embedded in Linear Elastic Soil Layers(Springer, 2020) İşbuğa, VolkanThis study proposes a new method to obtain the lateral response of pile groups by incorporating the pile group effect in layered soils. When a pile is loaded laterally, it creates a zone of influence in the direction of loading. In a pile group, each pile placed in the influence zone of prior piles is exposed to extra loads due to the load transfers from other piles. This mechanism results in a group effect which causes each pile in the group to have a different deflection curve compared to that of an identical isolated single pile under the same load. This study starts with a mathematical approach to model the interaction of two piles and then extends it to pile groups. The governing differential equation of a pile deflection problem is modified to take the pile-soil-pile interaction into account and solved analytically for each pile while the soil parameters and displacement fields around each pile are obtained numerically using the finite difference method written in Fortran language. The model captures the additional pile deflections induced by the group effects in pile groups and the results match well with the results of the existing methods, especially the finite element method.Master Thesis Impact of Urbanization on Hydrogeodynamic Systems: a Case Study: Bornova Region (i̇zmir, Turkey)(01. Izmir Institute of Technology, 2021) Öztürk, Bahadır; Baba, Alper; İşbuğa, VolkanUrbanization is one of the most critical processes affecting land and water use. Understanding urbanization and its impact on ground systems gained prominence with global climate change and population increase. This study focuses on the new city center Bornova Plain, İzmir; Turkey, used as agricultural land until the 1950s. Later, the region was opened for settlement, and excessive urbanization decreased the hydraulic conductivity of the surface area of the plain with the constructed buildings, road pavements, and other surface coverings. Effects of the land use- land cover changes on the hydrodynamic system of Bornova Plain's aquifers were investigated in three parts. Firstly, GIS-based hydrological models with two different periods (2004 and 2020) scenarios were developed with ArcSWAT for this thesis. Using SWAT models, elements of the water budget equation were determined. With SWAT Models, Recharge/Precipitation, Streamflow/Precipitation, and Baseflow/Total flow ratios were found to decrease 52%, 26.09%, and 11.86%, respectively, and Surface Runoff/Total Flow, and ET/Precipitation ratios were found to increase 20.59%, and 15.09% with urbanization increment comparing 2004 and 2020. Secondly, soil's bearing capacity changes with groundwater level changes within a year were investigated using five observation wells. Conceptual models were created for each well. Maximum of 14.82% of bearing capacity change was observed in the wells. Thirdly, PLAXIS 3D models were created to understand the effect of the groundwater level changes on pile settlements for sandy and clayey soils in the region. Conceptual models created and maximum of 12.74% settlement difference was observed for different groundwater levels.Article Citation - WoS: 1Citation - Scopus: 1Effect of Urbanization on Groundwater Resources Hydrodynamics and Bearing Capacity: a Case Study From the Bayraklı Region, Izmir, ̇ Türkiye(Geological Society of London, 2024) Öztürk,B.; İşbuğa,V.; Bilgiç,E.; Baba,A.The bearing capacity of soil is a critical factor in the design of foundations for civil engineering structures. The bearing capacity depends on soil properties, as well as the location of the water table. A rise in the groundwater level can be dramatic, especially in highly urbanized regions, and can affect the bearing capacity of foundations. In this study, groundwaterlevel fluctuations in a highly urbanized region in Izmir, the third largest city in Türkiye, was monitored over a 1 year period, and ̇ its effect on reducing the bearing capacity, which is not considered in foundation design and construction, was investigated. For this purpose, four observation wells equipped with groundwater data loggers were used to determine the variations in groundwater level over 1 year. Using the Terzaghi approach to calculate the bearing capacity, normalized bearing capacity plots for various foundation width/depth (B/Df) ratios were generated for all four observation wells. Remarkable bearing capacity changes of 10.94, 8.21, 7.62 and 9.29% were observed in four different observation wells (OW-1, OW-3, OW-6 and OW-9, respectively). The study showed that changes in groundwater level in the region caused by urbanization poses a potential risk to the sustainability of previously constructed foundations. © 2024 The Author(s).Master Thesis Response of Vertically Loaded Energy Piles Under Earthquake Excitation(2023) İnayet, Mehmet Göktuğ; İşbuğa, VolkanPile foundations are deep foundation systems that are used to transfer loads from superstructure to soil by either resisting surface friction or reaching a deeper and stiffer soil layer when geotechnical properties of the soil site are not sufficient to carry the loads transferred from superstructure. Energy piles fulfill the same function along with the ground heat exchanging via heat pump systems, thus satisfying the energy demand of a building for heating-cooling operations. This feature of energy piles draws attention as an innovative system supplying a renewable energy resource. However, heat exchanging operations of energy piles cause temperature variations on pile and the surrounding soil which may cause additional load and deformations. Moreover, temperature variations may affect the elasticity modulus of soils and shear strength of cohesive soils. In this study, earthquake response of an axially energy loaded pile was investigated considering the heating effect under 2020 Izmir earthquake motion using finite element method and compared to the those of identical regular piles. We performed analyses with different soil types, geometric properties, and temperature magnitudes under steady-state heating. Based on the analysis results, heating effect on pile head stiffness with respect to geometric properties were obtained. Two important conclusions have been made; (i) the most critical effect on heating depends on mechanical loading condition of pile and thermal expansion coefficient of soil, (ii) geometric properties may affect the temperature distribution resulting in an unforeseen change in pile head stiffness.Master Thesis Modelling Vertically Loaded Pile Groups by Considering Pile-Soil Interactions(2023) Kamış, Ömer Faruk; İşbuğa, VolkanThe aim of the study presented in this thesis is to create a model that takes into account the interaction between piles for the analysis of pile groups embedded in a linear elastic medium. This research builds upon prior work by Vallabhan and Mustafa (1996) introduced a single pile model and the pile-soil-pile interaction model proposed by İşbuğa (2023). The model has undergone further development to encompass the entire spectrum of pile groups regardless of how many piles it has and what kind of layout it has. This comprehensive model addresses two distinct scenarios: one involving a free-head pile group and another featuring a pile group that has a rigid pile cap. In the context of a free-head pile group, single piles within the group show different displacements due to load and interactions. On the other hand, in the case of a rigid pile cap, the piles must have equal displacements because of the rigid nature of the pile cap. Two different algorithms have been developed for both of these scenarios, and these algorithms have been implemented using the Python programming language. The model has been used to analyze various pile groups, and the analysis results were compared with previous studies and finite element method solutions. In addition to comparing the results, the computation times of the models proposed by this study and those of the finite element method were also compared.Article Citation - WoS: 29Citation - Scopus: 32Plate Loading Tests on Clay With Construction and Demolition Materials(Springer Verlag, 2021) Cabalar, Ali Fırat; Abdulnafaa, Mohammed Dafer; İşbuğa, VolkanThis study presents a series results of plate loading tests on a clay with various construction and demolition (CD) materials conducted in a large-scale model box and a numerical verification on the use of these material mixtures. The tests have been applied to the clay with three different types of CD materials (concrete, asphalt, and brick) prepared in a reinforced concrete circular box with a diameter of 2.0 m and a depth of 1.5 m. The CD materials were added to the clay with a mix ratio of 10% by dry weight and then compacted at optimum water content (w(opt)) and corresponding maximum dry density (gamma(drymax)). The testing results have indicated that the CD materials increased the ultimate bearing capacity of the clay with a range of 50-75%. Furthermore, a remarkable correlation between the results of plate loading tests and numerical simulations made by a commercial finite element software (Plaxis 2D) was observed for all mixtures tested.Article Citation - WoS: 1Citation - Scopus: 1The Modified Vlasov Model on a Nonhomogeneous and Nonlinear Soil Layer(Elsevier, 2022) İşbuğa, Volkan; Çerezci, Mehmet; Aşık, M. ZülfüThis study presents a novel approach to account for the soil nonlinearity of nonhomogeneous soil deposits in foundation deflection analyses in the context of a modified Vlasov foundation model. We present an extension of the previously proposed formulation by developing a new formulation employing an improved algorithm that takes the modulus degradation curves at varying strain levels into account in an iterative manner. This new model, which takes the nonlinear soil behavior into account, was first verified against a linear elastic soil model given in the literature to ensure that the new model algorithm can capture the original solution when the soil behavior is assumed to be linear elastic. Later, the experimental data reported in the literature for a specific type of dense and loose sands were used in the example analyses. Example problems were considered for different cases, which presented (i) how the model captures nonlinear behavior and (ii) the significant effect of the nonlinear soil behavior. The result of the new model was also compared with the finite element model results, assuming elastoplastic soil. The results obtained from both models match well, especially for the maximum deflection value, provided that laterally constrained sections underneath the foundation are used.