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    A comparative study to determine earthquake-induced settlements in sands
    (E Schweizerbartsche Verlagsbuchhandlung, 2024) Koltuk, Serdar; Subasi, Ozan; Iyisan, Recep; Fernandez-Steeger, Tomas
    Time and again earthquake-induced damage occurs worldwide as a result of soil liquefaction, especially in loose sands with high groundwater levels. One of the most common types of damage caused by liquefaction results from vertical soil deformations, in other words settlements. This article contributes to the determination of earthquake-related settlements in dry and saturated sands using two-dimensional finite element analyses (2D-FEA) and semi-empirical methods. The comparison of the results obtained from both methods showed that the 2D-FEA give relatively low settlement values compared to the values obtained from the semi-empirical methods. This is mainly explained by the relatively large horizontal earthquake accelerations resulting from the one-dimensional, equivalent-linear dynamic analyses and by the accumulation of earthquake waves at the upper edges of the numerical models.
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    A numerical study on liquefaction induced settlements by using PM4Sand model
    (2021) 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.
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    Öğe
    A numerical study on the estimation of liquefaction-induced free-field settlements by using PM4Sand model
    (Korean Society of Civil Engineers, 2021) Subaşı, Ozan; Koltuk, Serdar; İyisan, Recep
    The present paper treats the estimation of liquefaction-induced, free-field settlements using two-dimensional, fully coupled, finite element (FE) analyses. The PM4Sand model is used to simulate the liquefaction behavior of a homogeneous sand layer with three different relative densities of 35%, 55%, 75% under eleven different strong ground motions. The results of FE analyses are compared with those obtained from the well-known, semi-empirical methods in the literature. The numerical analyses show that, in case of a relative density of 35%, in general, the majority of earthquake-induced settlements occur in the period, in which the excess pore water pressure resulting from the strong ground motion begins to dissipate. The liquefaction-induced settlements are influenced by not only the moment magnitude and peak ground acceleration, but also other parameters of the ground motion. Furthermore, it has been shown that the evaluation of the liquefaction potential using finite element and semi-empirical methods gives similar results. However, the semi-empirical methods yield mostly larger settlements than those obtained from the FE analyses.
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    Öğe
    Assessment of liquefaction potential during earthquakes by using SPT-number of blows and two-dimensional finite element analyses
    (Springer, 2022) Koltuk, Serdar; Subaşı, Ozan; Fernandez-Steeger, Tomas; İyisan, Recep
    For the planning and design of buildings in earthquake zones with high groundwater levels, the liquefaction potential of the building site has to be investigated and evaluated. In DIN EN 1998-5:2010-12 (2010), the diagrams based on SPT-number of blows are given for the assessment of liquefaction potential. In the present study, this method is first described according to the current state of knowledge. Subsequently, the liquefaction potential of a sandy soil is analyzed using SPT-number of blows and two-dimensional finite element analyses (2D-FEA) with the sand-plasticity model PM4Sand. With respect to the assessment of liquefaction potential, a good agreement between the results obtained from both methods is found. Furthermore, the use of 2D-FEA with the PM4Sand model allows the estimation of earthquake-induced deformations on the soil surface.