Abstract. The objective of this paper focuses primarily on the numerical approach based on two-dimensional (2-D) finite element method for analysis of the seismic response of infinite soil-structure interaction (SSI) system. This study is performed by a series of different scenarios that involved comprehensive parametric analyses including the effects of realistic material properties of the underlying soil on the structural response quantities. Viscous artificial boundaries, simulating the process of wave transmission along the truncated interface of the semi-infinite space, are adopted in the non-linear finite element formulation in the time domain along with Newmark's integration. The slenderness ratio of the superstructure and the local soil conditions as well as the characteristics of input excitations are important parameters for the numerical simulation in this research. The mechanical behavior of the underlying soil medium considered in this prediction model is simulated by an undrained elastoplastic Mohr-Coulomb model under plane-strain conditions. To emphasize the important findings of this type of problems to civil engineers, systematic calculations with different controlling parameters are accomplished to evaluate directly the structural response of the vibrating soil-structure system. When the underlying soil becomes stiffer, the frequency content of the seismic motion has a major role in altering the seismic response. The sudden increase of the dynamic response is more pronounced for resonance case, when the frequency content of the seismic ground motion is close to that of the SSI system. The SSI effects under different seismic inputs are different for all considered soil conditions and structural types.

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Earthquakes have caused colossal casualties and severe damages to engineering structures and especially leading to substantial economic loss to the underground structures and/or infrastructures. Pipelines are one of most important component of lifeline engineering. For instance, the Southern Caucasus-Eastern Turkey energy corridors are formed by several key pipelines carrying crude oil and natural gas from Azerbaijan, via Georgia, to world markets through Mediterranean Sea. Many project accomplished recently and construction of new corridors are still going on. They should be protected from earthquake disaster especially when they pass through high seismicity zones. The installation of wave impeding barriers (WIB) below the vulnerable infrastructures as pipelines established in soft soil can be used to reduce the effect of the earthquake induced ground borne vibrations. In this paper, a WIB as artificial bedrock based on the cutoff frequency of a soil layer over bedrock is proposed as isolation measurement in order to mitigate the dynamic response of the buried pipelines under earthquake strong ground motion. The computational simulation of the wave propagation problem is directly achieved by employing nonlinear 2D finite element modelling for prediction of screening performance of WIB on the dynamic response of vibrating coupled soil-pipeline system. Energy absorbing boundaries along the truncated interfaces of the unbounded nature of the underlying soil media are implemented in the time domain along with Newmark's integration. An extensive parametric investigation and systematic computations are performed with different controlling parameters. The obtained numerical results point out that WIB can be very promising as an isolator to protect pipelines when they establish for a certain depth.

ÖZETHızlı demiryolu hattına yakın yapıları yumuşak zemin koşullarında taşınan kuvvetli titreşimlerden korumak için dalga bariyeri olarak yapay anakaya modeli inşaat mühendisliğinin pratik uygulamalarında kullanılmaktadır. Bu çalışmada, yüksek hızlı tren trafiğinin meydana getirdiği titreşimlerin demiryolu ağının çevresindeki binalarda oluşturduğu etkilerin azaltılması için dalga engelleyici bariyerlerin yerleştirilmesi araştırılmıştır. Yapay anakayanın aktif ve pasif yalıtım durumlarına göre performansını değerlendirebilmek için ayrıntılı parametrik çalışmalar gerçekleştirilmiştir.Anahtar Kelimeler: Yapay anakaya, yüksek hızlı tren, alüvyon zeminlerde dalga yayılımı, sonlu elemanlar metodu, doğrusal olmayan malzeme davranışı USING ARTIFICIAL BEDROCK IN MINIMIZING THE EFFECTS OF VIBRATION INDUCED BY HIGH SPEED TRAINS ON THE NEARBY STRUCTURES IN ALLUVIAL SOILS ABSTRACTAn artificial bedrock as wave impeding barrier can be used in practical civil engineering applications as isolation measures to protect structures from strong vibrations transmitted through soft ground nearby high-speed railway track. This study focuses on mitigation of the effects of high speed trains inducued vibrations on the strucutres which are located near the track lines by installing wave impeding barriers. Extensive parametric studies on the screening performance of wave impeding barrier have been done for both active and passive isolation cases.Keywords: Artificial bedrock, high speed train, wave propagation in alluvial soils, finite element method, nonlinear behaviour of soil