Prof. Dr. Gürkan Özden danışmanlığındaki tezler
10 tez · Dokuz Eylül University
A study on optimization of piled rafts
In this study, optimum design principles of piled rafts are investigated using settlement based design approach. Settlements are calculated using the simplified method of Randolph and finite element analysis with Plaxis 3D software. Load sharing between the raft and pile group is taken into account in Randolph method, since the contribution of raft to load carrying capacity of the overall foundation system is the basis of piled raft approach. A case study is introduced in order toreach an optimum solution in terms of settlement based design. Optimum design is investigated in two stages. In the first stage, effect of number of piles on settlement behaviour of piled rafts is investigated. The aim of first stage is to reach an economical solution. In the second stage, total pile quantity is kept constant and it is aimed to seek satisfactory behaviour in terms of settlements.It is shown that the optimum solution may be reached by increasing pile length rather than number of piles. Stiffness of a pile group is not equal to sum of single pile stiffness due to the interaction among piles. Group efficiency coefficient is used for taking into account the interaction effect and an emprical equation is suggested for efficiency factor. The proposed equation consists of an interaction term and non-linearity term which are based on Randolph and Caputo&Viggianiapproaches, respectively. Validation of the suggested equation is investigated by comparing with the results of two case studiesthat field measurements are available in the literature.It is shown that settlements estimated by means of the suggested equation are in good agreement with the measured values.
Ondört katlı bir yapı temelinin yüksek binalar için İzmir yerel teknik önermesine göre analizi
The goal of this study is to investigate use of İzmir Local Technical Advisory for Tall Buildings by means of analyses of the foundation system of a sample building. The building is considered to be situated on the east coast of İzmir Bay Area and its inertial soil-structure interaction analyses were made. Computations were performed obeying the procedure as defined by NEHRP. The dynamic stiffness of the pile group was obtained according to Makris-Gazetas approach. A software was developed for this purpose and achieved results were compared with those from the DYNAN software. The flexible behavior of the foundation was taken into consideration by distributing the computed group stiffness within the foundation zones. Influence of this zonation approach on the building period required application of an iterative procedure. Iterations continued until computed dynamic group stiffness values with respect to the building period converged. The D1, D2 and D3 level response spectra produced according to the DLH Technical Standard were utilized as the target spectra while performing dynamic analyses of the buildings being designed in the area. The acceleration-time records that were necessary in this respect were selected from the PEER Ground Motion Database. The ground motions at the foundation level of the building were computed through one-dimensional site response analyses. Variation of shear wave velocity with depth was deduced using geophysical field tests whereas other conventional soil mechanics data were acquired based on the soil mechanics laboratory test results. Such data obtained at various locations and depth levels were used while establishing the idealized soil profile. Two different rock levels were assumed in the idealized soil profile during dynamic analyses. These were the engineering bedrock and the seismic rock levels yielding two sets of ground motion records at the foundation level. The results of time-domain structural analyses were then compared. It was found that the analyses that were made using engineering bedrock level ground motion set yielded results that stay on the unsafe side.
Geniş yeraltı metro istasyonlarının inşasında yeni Avusturya tünel inşaat yönteminin uygulanabilirliğinin incelenmesi
Tunneling, as it was in the past, remains an essential construction activity today, serving purposes such as water supply, sewage, drainage, and transportation to meet humanity's basic needs. The increasing population and fundamental requirements, especially in the field of transportation, have necessitated tunnel construction within urban areas. During tunnel excavations, deformations occur within a specific influence area of the tunnel. These deformations can particularly damage structures around the tunnel, and in the event of tunnel collapse, they can even lead to settlement in buildings. To prevent these deformations, it has been emphasized that the geological, hydrological, geotechnical characteristics of the tunnel excavation area, as well as the carefully selected tunnel depth and diameter, need to be thoroughly examined. The anticipated levels of deformation before tunnel excavations were initially predicted using empirical methods proposed by various researchers. These values were then compared with site measurements and analyses conducted using the finite element method. While empirical methods and FE analysis results showed similar values, greater deformations were observed in site measurements. This was attributed to the precision displayed during site excavations. With the existing methods, the anticipated surface settlements were found to be beyond acceptable limits, prompting additional measures and improvements to mitigate these deformations within the scope of this thesis. The conducted work demonstrated that deformations decreased by approximately 36-43 percentage compared to the existing situation.
Bilgi tabanlı bir geoteknik öğrenme ve veritabanı platformunun geliştirilmesi
Geotechnical engineering is still an emerging branch of civil engineering within modern soil mechanics, which has seen tremendous technological advancements across various domains in recent times. The global effects of COVID-19 pandemic have led to significant changes in education, industry, and research, including the geotechnical field of civil engineering. Geotechnical databases have gained eminence in literature, driven by the rapid growth of online resources. However, problems related to availability, accessibility, and collaboration continues. This study aims to support the geotechnical knowledge in undergraduate and graduate education by introducing "Geo-Minds", a knowledge-based geotechnical learning platform. The platform covers topics such as pile foundations and soil mechanics, using a user-friendly interface built on the WordPress content management system. Its efficiency is demonstrated through an online survey, manifesting positive responses from engineers, educators, and those interested in the field. Geo-Minds aspires to improve geotechnical education and practice, being powered by the evolving technology in online education.
Yetersiz kalan geoteknik çalışmalarda kusurun sorumlu taraflar arasında paylaştırılmasında güvenilirliğe dayalı yöntemlerin kullanılması
Increasing number of problems and disputes resulting from these problems have been observed in the construction and utilization phases of the residences, infrastructures and engineering structures that have been accelerated recently in our country. As there are no competent persons or organizations that might be referee between the parties, settlement of these legal disputes is looked for in the jurisdiction system. According to the Turkish Law system, the "legal expertise" is frequently consulted for the settlement of a case requiring special knowledge and technical legal expertise within the aim of helping the judge to understand the related case, to analyze the complex and contradictory parts of the case and to the make the best judgment. Risk and uncertainty is indispensable in the design, application or management issues related to geotechnical engineering. Compared to the uncertainties present in the other divisions of the civil engineering, one can see that the uncertainties and risks are at a much higher level in geotechnical engineering. Despite the huge contribution of the scientists in the theoretical issues and to the quality increased in the practice thanks to the developed technology; there are still structural damages that may end up with collapse or destruction in the field of geotechnical engineering applications. Naturally judicial rights are researched not only for the indemnification of these damages but also for the penal sanctions. The disputes related to the geotechnical engineering applications faced in Turkish Law System as well as the role and solution suggestions of the expert are presented in this study.
Dinamik yer tepki analizlerinin aşırı boşluk suyu basıncı gelişimi parametrelerine hassasiyeti
Geotechnical earthquake engineering studies the problems arising from the behavior of soils under earthquake loading. The biggest uncertainties in these problems are the selection of the earthquake record and the determination of the soil parameters. In this study, the behavior of the soils of the Izmir region under earthquake loading has been examined using 1-dimensional ground response analyses. Acceleration records recorded at the stations during the 30 October 2020 Samos earthquake were used in the analyses. In addition to outcrop records, ground surface records are also available at the stations. Accordingly, the ground surface station was defined as the input motions, and the rock record in the region was obtained by 1-dimensional analysis. The obtained rock record was given to another station site whose soil profile is known, and the results were compared with the recorded motions. When the exposure records at different stations were applied as input in a certain area, results that were not close to the ground surface were obtained. MKZ and GQ/H models were used in nonlinear analyses. The effects of these models on the results were demonstrated by comparing the response spectra obtained on the ground surface. Overall, the MKZ model has been shown to damped the motion reaching the ground surface. In the GQ/H model, on the other hand, high spectral accelerations were obtained in the high period region of the response spectrum. In addition, the analyses were repeated by increasing the shear wave velocity by 20%. Accordingly, the closest result to the acceleration recorded in the station was obtained when the MKZ model and 20% increased shear wave velocity profile were used. These results revealed the effect of the errors caused by the inability to model the soil behavior on the results obtained.
Ortogonal baret kazıklarda zemin-yapı-zemin etkileşiminin araştırılması
In recent years, tall building design and construction accelerated in Turkey. Barrette piles have been preferred over circular bored piles due to their higher load-bearing capacity and bending stiffness to carry induced loads by the superstructure. In this thesis, four different cohesionless soils with different relative densities and different pile spacings were modeled in order to investigate the pile groups under lateral loads. Barrette piles were modeled as volumetric elements in order to examine shape effects more accurately. In this context, the effects of the cross-section and orientation of the piles in the group, spacing between the piles, the soil stiffness and the magnitude of loading on the behavior of the group barrette piles were investigated under linear and nonlinear soil conditions. Considering these effects, the horizontally loaded barrette pile groups were analyzed in the finite element program and the interaction factors between the piles were calculated. Since the cross-sections of the barette piles are rectangular, the most important factor in their interaction with each other was the bending stiffness of the pile in the direction of the load acting on the pile. Analysis results revealed that the interaction between barrette piles is quite different from that of circular piles, mostly depending on the type of pile cross section. In addition, it was concluded that the shading effect is quite effective for both free and fixed head pile groups. Keywords: Lateral loaded piles, interaction factor, barrette pile, pile orientation, pile-soil-pile interaction.
Atalet yükleri altında zemin-kazık etkileşimine bağlı olarak aşırı boşluk suyu basıncı gelişimi mekanizmasının incelenmesi
The behavior of piles in submerged and liquefiable sandy soils under earthquake loads has attracted the attention of researchers since the 1980s. This study investigated the behavior of soil surrounding piles in such soils. In the study, the lateral response of the pile due to inertial and kinematic interaction was considered, and it was assumed that the soil was in passive terms during the earthquake. As a liquefiable soil layer, sandy soil whose liquefaction model parameters were determined at the California Wildlife Test Site was considered. In the inertial interaction analyses made under different horizontal loads and frequencies, it was determined that the stresses transferred from the pile to the soil could force the soil up to liquefaction by causing excess pore water pressure to change in the soil and its reflection on the horizontal load-displacement curves (p-y curves) is discussed. The analysis results revealed that the loading frequency had some effect on soil behavior, and the development of excess pore water pressure significantly affected the horizontal load-displacement curves. In kinematic analyses, the presence of inertial loading has been found to be less influential on excess pore pressure generation with depth than in the free-field case. It is detected that the influence of the pile on excess pore water pressure quickly diminishes with the horizontal distance for a particular depth. It is shown that Loading intensity affects the amount of induced pore pressures. The gap between the pile and free field displacements gradually developed as dynamic loading progresses.
Sıvılaşan zeminlere oturan rıhtım duvarlarının sonlu elemanlar analizleri
In this thesis, back analyses of No.6 Gravity Quay Wall of Derince Port which is one of the several damaged coastal structures in August 1999 Marmara Earthquake, was made. The site reports after the earthquake revealed that the quay wall faced damages in terms of lateral and vertical displacements due to liquefaction of the backfill. Dynamic finite element method was utilized during the analyses in which response of the liquefiable soil was taken into consideration by means of UBC3D-PLM material model. Earthquake motion was defined at the bedrock level using three earthquake records, two of which occurred on the North Anatolian Fault. Analyses results showed that response of the liquefiable backfill should be discussed considering soil-structure interaction and frequency content of the earthquake records. The simple excess pore pressure dissipation technique provided on wall blocks could considerably enhance earthquake response of the quay wall.
Suya doygun zemin profillerinde doğrusal olmayan efektif gerilme analizleri yoluyla dinamik zemin büyütmesi
Seismic waves from bedrock during their propagation are affected by the properties of the layer through which they passed; there may be changes in time, frequency and amplitude. Seismic waves is affected by local condition such as bedrock depth, thickness of soil layer, dynamic properties, lateral discontinuity of the soil and topographical properties. In this study, how to the effects of local condition on soil response analysis were investigated. One-dimensional (1D) nonlinear site response analyses were performed using DEEPSOIL software in an area located on the coast of the Izmir Bay where of deep alluvial soils govern the local geology. The soil profile is predominantly composed of thick clay layers and occasional sand-gravel layers in the study area. Nonlinear analyses were performed with the acceleration-time records that are taken from the PEER Ground Motion Database. In this study, two different bedrock levels are studied during dynamic site response analyses. The free field design spectra obtained by bedrock level depth of 240m with nonlinear methods were compared with those obtained by bedrock level depth of 1000m using effective and total stress based nonlinear methods. Also specific site response analyses results were compared code-based design. Results of the study showed that model depth and effective stress analysis affect site response analysis significantly and also obtained response spectra according to code-based was more conservative than according to the specific site response analysis. The other important result of the specific site response analysis is extension of the period.