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Wyświetlanie 1-3 z 3
Tytuł:
On determining the undrained bearing capacity coefficients of variation for foundations embedded on spatially variable soil
Autorzy:
Chwała, Marcin
Powiązania:
https://bibliotekanauki.pl/articles/178626.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
spatial averaging
random field
random bearing capacity
fluctuation scale
failure mechanism
Opis:
This paper presents an efficient method and its usage for the three-dimensional random bearing capacity evaluation for square and rectangular footings. One of the objectives of the study is to deliver graphs that can be used to easily estimate the approximated values of coefficients of variations of undrained bearing capacity. The numerical calculations were based on the proposed method that connects three-dimensional failure mechanism, simulated annealing optimization scheme and spatial averaging. The random field is used for describing the spatial variability of undrained shear strength. The proposed approach is in accordance with a constant covariance matrix concept, that results in a highly efficient tool for estimating the probabilistic characteristics of bearing capacity. As a result, numerous three-dimensional simulations were performed to create the graphs. The considered covariance matrix is a result of Vanmarcke’s spatial averaging discretization of a random field in the dissipation regions to the single random variables. The matrix describes mutual correlation between each dissipation region (or between those random variables). However, in the presented approach, the matrix was obtained for the expected value of undrained shear strength and keep constant during Monte Carlo simulations. The graphs were established in dimensionless coordinates that vary in the observable in practice ranges of parameters (i.e., values of fluctuation scales, foundation sizes and shapes). Examples of usage were given in the study to illustrate the application possibility of the graphs. Moreover, the comparison with the approach that uses individually determined covariance matrix is shown.
Źródło:
Studia Geotechnica et Mechanica; 2020, 42, 2; 125-136
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An iterative algorithm for random upper bound kinematical analysis
Autorzy:
Chwała, Marcin
Powiązania:
https://bibliotekanauki.pl/articles/2073758.pdf
Data publikacji:
2022
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
random bearing capacity
shallow foundation
scale of fluctuation
iterative algorithm
upper bound
spatial variability
Opis:
A new approach for stochastic upper bound kinematical analyses is described. The study proposes an iterative algorithm that uses the Vanmarcke spatial averaging and kinematical failure mechanisms. The iterative procedure ensures the consistency between failure geometry and covariance matrix, which influences the quality of the results. The proposed algorithm can be applied to bearing capacity evaluation or slope stability problems. The iterative algorithm is used in the study to analyse the three-dimensional undrained bearing capacity of shallow foundations and the bearing capacity of the foundation for two-layered soil, in both cases, the soil strength spatial variability is included. Moreover, the obtained results are compared with those provided by the algorithm, based on the constant covariance matrix. The study shows that both approaches provide similar results for a variety of foundation shapes and scale of fluctuation values. Therefore, the simplified algorithm can be used for purposes that require high computational efficiency and for practical applications. The achieved efficiency using a constant covariance matrix for one realisation of a three-dimensional bearing capacity problem that includes the soil strength spatial variability results in about 0.5 seconds for a standard notebook. The numerical example presented in the study indicates the importance of the iterative algorithm for further development of the failure mechanism application in probabilistic analyses. Moreover, because the iterative algorithm is based on the upper bound theorem, it could be utilised as a reference for other methods for spatially variable soil.
Źródło:
Studia Geotechnica et Mechanica; 2022, 44, 1; 13--25
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photogrammetric evaluation of body posture of 6-year-old boys training judo, in three repeated assessments
Autorzy:
Walaszek, Robert
Chwała, Wiesław
Sterkowicz-Przybycień, Katarzyna
Burdacka, Katarzyna
Burdacki, Marcin
Kurowski, Paweł
Powiązania:
https://bibliotekanauki.pl/articles/306731.pdf
Data publikacji:
2019
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
postura
aktywność fizyczna
dżudo
body posture
photogrammetry
physical activity
judo
Opis:
The purpose of this work was to assess changes in body posture in a group of 6-year-old boys training judo, compared to a control group, in three repeated examinations. Methods: The study included 88 boys aged 6. Fifty-one of them started judo training in sports clubs at the beginning of the school year (JU). The control group included 37 boys attending reception classes in primary schools, selected at random (NT). Body posture was assessed 3 times at 3-month intervals, according to the general methodology of the Moire’s technique, and 15 body posture indices were obtained as a result: 7 in the sagittal plane, 1 in the axial plane and 7 in the coronal plane. The system for photogrammetric body posture assessment of CQ Elektronik System was used in this study. Results: The ANOVA test showed that neither the group factor – the fact of judo training – nor the time factor had any significant effect on the number of “deviations from normal values” of body posture ( p > 0.05). Statistically significant intergroup differences were noted for six body posture indices measured with the Moire’s method. Conclusions: Steadily decreasing numbers of “deviations from normal values” of body posture indices in the JU group were observed over the three examinations. Regular 6-month judo training had a statistically significant effect on a decrease of body rotation in the axial plane – the effect of judo training may be considered corrective in this case.
Źródło:
Acta of Bioengineering and Biomechanics; 2019, 21, 3; 149-157
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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