Mühendislik Fakültesi
https://hdl.handle.net/20.500.12846/16
2024-03-29T14:10:56ZPull-out strength of screws in long bones at different insertion angles: finite element analysis and experimental investigations
https://hdl.handle.net/20.500.12846/943
Pull-out strength of screws in long bones at different insertion angles: finite element analysis and experimental investigations
Gepek, Engin; İyibilgin, Osman; Bayam, Levent; Drampalos, Efstathios; Shoaib, Amer
Different types of plates are available to allow
insertion of screws for internal fixation of long bone fractures. The aim of the study was to determine the effect of the
insertion of screws at different angles on a long bone to the
pull-out strength. Using 3D printed bone models, we tested
the pull-out strength of screws in long bones at insertion
angles between 0 and 40° with both finite element analysis
and on printed models experimentally and compared the
results. Test samples and cortical screws used were modeled
with SolidWorks software and analyzed with Ansys software. As the screw insertion angle increases, the pull-out
forces on the test specimens increase from 61.14 ± 3.5 N at
0° to 273 ± 6.8 N at 40° with an exception of a small drop
between 15 and 20° from 235.4 ± 6.2 to 233 ± 6.9 N. Both
methods showed an increase in the pull-out strength of
screws as the insertion angle increases. This might be
applicable in the clinical practice of bone fixation. Further
studies on plate and screw fixation are needed to complement the findings.
2024-01-01T00:00:00ZDetermination of local site soil conditions by microtremor measurements for sustainable buildings
https://hdl.handle.net/20.500.12846/942
Determination of local site soil conditions by microtremor measurements for sustainable buildings
Subaşı, Ozan; Özaslan, Bilal; Haşal, Murat Emre; Hiroaki, Yamanaka; Chimoto, Kosuke
As well known, local soil condition at a specific site affects the significant features of strong ground motion such as amplitude, frequency range and time duration. The effects of site condition depend on the properties of the motion characteristics, material properties, topography and geometry of the field. The bedrock slope at the basin sides also is one of the most important factors in the response analyzing of a specific site in geotechnical earthquake engineering applications. The reflection and refraction waves from the basin edges induce the wave transmission and two dimensional effects. In this case two dimensional site response analyses are required to estimate the behavior of the soil layers. So, local geotechnical site condition should be into account in the design of earthquake resistant building. The bedrock slope of the basin edges should be determined for suitable method in two dimensional dynamic response analyses. In this study, the result of a specific site response based on shear wave velocity profiles determined by microtremor array measurements are presented. The geotechnical properties of the soil layers were obtained from the previous subsurface explorations. Seismic bedrock depth and bedrock slope of the edge were defined by microtremor array measurements. Shear wave velocity value is from ten to hundred meters was obtained from passive surface wave method by employed Spatial Auto Correlation algorithm. Established variation of shear wave velocity with depth models were examined in terms of local site amplification. In order to verify consistency of obtained amplification numbers, empirical and measuremental results were compared for each site. As a conclusion, dynamic properties of local site conditions under earthquake excitation were described in terms of maximum amplification, resonance frequency and predominant period.
2018-01-01T00:00:00ZA numerical study on liquefaction induced settlements by using PM4Sand model
https://hdl.handle.net/20.500.12846/941
A numerical study on liquefaction induced settlements by using PM4Sand model
Koltuk, Serdar; Subaşı, Ozan; Akbaş, Merve; Iyisan, Recep
The destructive effects of earthquakes negatively affect many people's lives
and cause a large number of lives and property losses. One of the most crucial factors that
increase the destructive effects and structural damages of earthquakes is the deformations in the
soil layers during strong ground motion. Especially liquefaction due to sudden increase in pore
water pressure during strong ground motion in saturated sandy soils causes large deformations
in the soil layers; hence leads to severe damage to the structures. Therefore, it is necessary to
determine the liquefaction-induced deformations and settlements in the soil layers with high
liquefaction potential. Following this purpose, three different two-dimensional fully saturated
soil profiles with 35, 55, 75 % relative densities were created and carried out by using different
strong ground motions for estimation of liquefaction-induced free field settlements. The finite
element code "Plaxis 2D" and constitutive model "PM4Sand" were used in the analysis. The
results of finite element (FE) analyses were compared with semi-empirical methods in the
literature. The liquefaction state observed with pore pressure ratio (Ru) and safety factor (FS) is
similar in numerical and empirical methods. The FE analyses have shown that the evaluation of
free-field, liquefaction-induced settlements obtained from PM4Sand-Model have considerably
lower settlement values than the semi-empirical methods. However, the semi-empirical method
suggested by Cetin et al. (2009) and numerical analyses gave quite similar settlement results to
each other. Moreover, there is no direct relationship between the liquefaction-induced
settlements and the earthquake source properties in the numerical method. However, this is
different for semi-empirical methods, and there is a relationship between strong ground motion
features and liquefaction-induced settlements.
2021-01-01T00:00:00ZSıvılaşma nedeniyle meydana gelen oturmaların Pm4Sand bünye modeli ile incelenmesi
https://hdl.handle.net/20.500.12846/940
Sıvılaşma nedeniyle meydana gelen oturmaların Pm4Sand bünye modeli ile incelenmesi
Subaşı, Ozan; Iyisan, Recep
Depremlerin yıkıcı etkisini ve yapısal hasarları arttıran en önemli faktörlerden biri, dinamik yükler altında zemin tabakalarında oluşan deformasyonlardır. Özellikle suya doygun kumlu zeminlerde, kuvvetli yer hareketi sırasında boşluk suyu basıncındaki ani artış nedeniyle meydana gelen sıvılaşmalar, zemin tabakalarında büyük deformasyonlara yol açmakta ve mühendislik yapılarında ciddi hasarlara neden olmaktadır. Bu çalışma kapsamında, rölatif sıkılığı %35,55,75 olan üç farklı kum zemin özellikleri kullanılarak iki boyutlu zemin profilleri oluşturulmuş ve on dört farklı kuvvetli yer hareketi kullanılarak doğrusal olmayan dinamik analizler bir sonlu eleman yazılımıyla gerçekleştirilmiştir. Kum zemin tabakalarının sıvılaşma davranışını modellemek için ise programda yer alan PM4Sand bünye denklemleri kullanılmıştır. Elde edilen numerik analiz sonuçları literatürde yer alan ve iyi bilinen yarı-ampirik yöntemlerle karşılaştırılmıştır. Buna ek olarak, kuvvetli yer hareketini tanımlamak için kullanılan parametrelerle, numerik ve yarı-ampirik analizler sonucunda elde edilen sıvılaşma kaynaklı oturmalar arasındaki ilişkiler incelenmiştir.; One of the most important factors that increase the destructive effects of earthquakes and structural damages is the soil deformations during strong ground motion. The liquefaction occurs especially in saturated sandy soils as a result of the sudden increase in pore water pressure during the earthquakes and leads to large deformations in the soil layer and serious damages to engineering structures. In this study, by using three different sand properties with relative densities of 35,55 and 75%, two-dimensional soil profiles were created and dynamic analyzes were carried out using fourteen different acceleration-time histories records. In the numerical analysis was performed with a finite element software and PM4Sand constitutive equations were used to model the liquefaction behavior of sand layers. The numerical analysis results were compared with the well-known semi-empirical methods in the literature. In addition, the relationships between the parameters used to define strong ground motion and the liquefaction-induced settlements obtained from numerical and semi-empirical analyzes were investigated.
2022-01-01T00:00:00Z