Erkan Çelebi

Three-dimensional modelling of train-track and sub-soil analysis for surface vibrations due to moving loads

Two mathematical models and numerical techniques for solving problems associated with the wave propagation in a track and an underlying soil due to passing trains are presented and compared. For the analysis, the thin layer method/flexible volume method (TLM/FVM) and the boundary element method (BEM) are employed to investigate the three-dimensional dynamic response of the free field nearby railway lines induced by the moving loads acting on the surface of a homogeneous or layered half-space. Particular interest is paid to influence of the mechanical properties of the railway track configuration on the vibrations covering surface propagation. A common feature of all simulation models is the application of the sub-structuring approach in the frequency domain. The results of the present numerical simulation are initially compared to an analytical and other numerical solutions. A comprehensive numerical investigations have been carried out to indicate the influence of different parameters on the amplitude reduction due to presence of an open trench. The results point out that using an open trench barrier with appropriate geometrical properties, a notable reduction level can be achieved.

The effectiveness of wave barriers on the dynamic stiffness coefficients of foundations using boundary element method

A comprehensive numerical investigation has been carried out to indicate the influence of wave barriers on the complex dynamic stiffness coefficients of the surface supported foundations under dynamic loads. In the considered problems the underground is regarded as an elastic homogeneous half-space and as a layer on the top of a rigid bedrock. The results of the present numerical simulation are obtained by using the substructure approach in the frequency domain which is formulated on basis of the boundary element method (BEM). The validations of the numerical results are shown through comparison with published numerical data. The results point out that using an open trench barrier with appropriate distance surrounding the vibration source, a notable reduction level can be achieved.

The evaluation of impedance functions in the analysis of foundations vibrations using boundary element method

The basic step in the substructure approach based on discretization of the soil medium for the soil-structure interaction problems is to determine the impedance functions which are defined as the complex dynamic-stiffness coefficients of the soil-footing system are used in the analysis of foundations vibrations. In this study, the discrete values of impedance functions over wide ranges of frequency-factors are presented for both surface-supported and embedded foundations. The numerical results are obtained by using the substructure approach in the frequency domain which is formulated on basis of the Boundary Element Method derived from the fundamental solution for a homogeneous, isotropic and linear-elastic continuum. To further demonstrate in practical applications and to show the solutions of this type of problems to civil engineers, a comprehensive parametric analysis and systematic calculations are performed with various controlling parameters to evaluate the dynamic response of the vibrating soil-foundation system. In addition, the solutions for normalized stiffness and damping coefficients of foundations in almost all cases of vibration modes are in very good agreement with the published results based on the analytical methods. The obtained numerical results should enable practicing engineers to take into account the linear soil-structure interaction problems over wide ranges of frequency factors.

Lateral load estimation from visco-plastic mud-flow around cylindrical row of piles

In this paper, the influence of slow and creeping flow of mud/slurry is modelled as a visco-plastic fluid around cylindrical row of piles. The study is carried out theoretically using principles of applied fluid mechanics. The research initiates from actual requirement in using a series of piled columns as barrier(s) to stabilise such slopes considered to be at risk of land-slide due to reduced stability. It was thought that in the event of slope failure, the homogenised behaviour of the moving mass could be modelled as a fluid with appropriate inertial and mechanical properties. Parametric studies were carried out to estimate forces on a row of piles, considering visco-plastic fluids with different mechanical properties. The analysis focused on determining the variation of force per a unit distance with depth on piles, under the influences of a number of key parameters.

Triplet Shear Tests on Masonry Units with and Without Seismic Textile Reinforcement

This research primarily aims to investigate experimentally the mechanical behavior and the crack pattern of the perforated brick block masonry specimens under shear stresses before and after reinforcing procedure with seismic textile. The reinforcing system is a combination between an inorganic matrix made with natural hydraulic lime and white cement and a hybrid multiaxial seismic textile made from Alkali Resistant (AR) glass and polypropylene fibers. The effect of the single-sided application of the sand plaster on the non-strengthened wall specimens is also tested to compare with both reference and retrofitted specimens. The obtained results of the triplet shear tests are given in the manner of force-displacement curves comparatively for all specimens considered without/with textile reinforcement. The shear strength for each triplet specimen investigated is also obtained. The effect of the presence of seismic textile as well as the applied sand plaster on the mechanical behavior of the triplet specimens is emphasized. It is concluded that the shear resistance and the ductility highly influenced by using the seismic textile and relevant plaster.

Wave Propagation and Vibration Isolation in Soils

The goal of this study is to deal with the modelling and calculation of the ground-borne vibrations and the effect of the wave propagation on foundation response with emphasis on vibration screening systems. Herein, ANSYS FEM software program was used to simulate vibratory source induced wave propagation and dynamic foundation-soil interaction problem. Extensive parametric investigations on the screening performance of open and in-filled trench barriers have been done for both active and passive isolation cases. The obtained results are important for structural engineers since provide practical information and methods about the dissipation of the strong vibration energy.

Doğalgaz boru hatlarında dalga bariyeri olarak yapay kaya dolgusunun dalga yayılışına etkisi

Depremler yeryuzunun buyuk bir kesimini etkileyerek muhendislik yapilarina ciddi hasarlar vermekte ve onemli ekonomik kayiplara yol acmaktadir. Bu yuzden, deprem etkisi altindaki boru hatlarinin dayanimi ve guvenligi hayati oneme sahiptir. Zemin titresimlerinin yayilma alaninda ve korunacak yapi cevresinde azaltmak icin yatay konumlandirilmis dalga bariyer uygulamalari insaat muhendisligi cozumleri arasinda yer almaktadir. Bu calismada yapi-zemin etkilesimi de dikkate alinarak 1999 Kocaeli depreminden kaynaklanan titresim etkilerinin azaltilmasi icin zeminin radyasyon sonumunu ifade eden enerji yutucu sinirlari ve dogrusal olmayan malzeme ozelliklerini de iceren bir numerik model gelistirilmistir. Gelistirilen bu model yardimiyla dalga bariyer sisteminde farkli kontrol parametrelerinin yalitim etkisi kapsamli parametrik calismalar yapilarak elde edilmistir. Elde edilen sonuclar dalga engelleyici yapay kaya dolgusunun titresim etkilerinin azaltilmasinda %70 mertebesinde etkili oldugunu ve bu tur problemler cozum olarak gelecekte uygulanabilecegini gostermektedir.

YAPAY ANAKAYA KULLANILARAK YÜKSEK HIZLI TRENLERİN ALÜVYON ZEMİNLERDEKİ ÇEVRE YAPILARDA OLUŞTURDUĞU TİTREŞİM ETKİLERİNİN AZALTILMASI

Hizli demiryolu hattina yakin yapilari yumusak zemin kosullarinda tasinan kuvvetli titresimlerden korumak icin dalga bariyeri olarak yapay anakaya modeli insaat muhendisliginin pratik uygulamalarinda kullanilmaktadir. Bu calismada, yuksek hizli tren trafiginin meydana getirdigi titresimlerin demiryolu aginin cevresindeki binalarda olusturdugu etkilerin azaltilmasi icin dalga engelleyici bariyerlerin yerlestirilmesi arastirilmistir. Yapay anakayanin aktif ve pasif yalitim durumlarina gore performansini degerlendirebilmek icin ayrintili parametrik calismalar gerceklestirilmistir.