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RISS 인기검색어
- 검색키워드
- 저자 : A. Ghahramani (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Stress Level Based Bearing Capacity of Foundations: Verification of Results with 131 Case Studies
M. Veiskarami,M. Jahanandish,A. Ghahramani 대한토목학회 2012 KSCE Journal of Civil Engineering Vol.16 No.5
Evidence of decreasing magnitude in the bearing capacity factor, Nγ , in shallow foundations requires a different strategy rather than taking a constant soil friction angle conventionally used in computation of this factor. Because of the influence of stress level on soil friction angle, a more complex analysis may be required to compute the values of Nγ since the mobilized soil friction angle at failure differs from point to point beneath shallow foundations corresponding to the experienced level of stress. This can be performed by taking a variable field of mobilized soil maximum friction angle which can be achieved by the aid of the Zero Extension Lines (ZEL)equations. It has been realized by the authors in developing design charts in which, variations of Nγ with foundation size have been presented by the stress level based ZEL method. Following previous attempts, this research is devoted to extending these charts to circular foundations and furthermore, to provide an in depth investigation of the possibilities and advantages of using these charts. A comprehensive foundation load test database has been collected and recompiled for this research to compare the predictions made by the ZEL method in the suggested design charts with field data. The predictions by these design charts show a reasonable coverage over the entire range of selected case studies presented in this research.
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Effect of Stress Level on the Bearing Capacity Factor, Nγ , by the ZEL Method
M. Jahanandish,M. Veiskarami,A. Ghahramani 대한토목학회 2010 KSCE Journal of Civil Engineering Vol.14 No.5
It has been known that soil shear strength parameters are stress level dependent. On the other hand, foundation size has a significant effect on the level of imposed stress on subsoil elements. In this study, the Zero Extension Lines (ZEL) method, which has wide applications in determination of bearing capacity and load-displacement behavior of foundations and retaining walls, is employed to consider the stress level dependent nature of soil shear strength parameters to predict the actual bearing capacity of foundations. The ZEL equations which are capable of considering variations in soil shear strength parameters have been employed to consider their dependency on stress level and solved numerically by a computer code developed for this study. The presented approach has been compared with experimental data showing reasonable predictions when the effect of stress level is taken into account. It is then utilized to develop some design charts showing modified values of Nγ , as a function of foundation size and soil properties based on Bolton (1986) equation for stress level effect in cases of smooth and rough base foundations. The charts represent the decreasing tendency in Nγ with an increase in foundation size and it shows the decreasing tendency in the reduction rate when the foundation size increases.
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Smith, S. B.,Go, G. W.,Johnson, B. J.,Chung, K. Y.,Choi, S. H.,Sawyer, J. E.,Silvey, D.T.,Gilmore, L. A.,Ghahramany, G.,Kim, K. H. Oxford University Press 2012 Journal of animal science Vol.90 No.8
<P>We have demonstrated that among carcass adipose tissue depots, brisket subcutaneous adipose tissue contains the greatest concentration of MUFA and lowest concentration of SFA. Therefore, we hypothesized that brisket subcutaneous adipose tissue depots would exhibit greater adipogenic gene expression over time than other major subcutaneous adipose tissue depots. Four Angus steers, each at 9, 12, 14, and 16 mo of age, were harvested and fresh subcutaneous adipose tissue samples were collected from over the brisket, chuck, rib, loin, sirloin, round, flank, and plate. Relative gene expression for C/EBPβ, PPARγ, carnitine palmitoyltransferase-1 beta (CPT-1β), stearoyl-coenzyme A desaturase (SCD), AMP-activated protein kinase alpha (AMPKα), and G-coupled protein receptor 43 (GPR43) was analyzed by quantitative real-time PCR. Expression of C/EBPβ, PPARγ, and CPT-1β was greatest at 12 to 14 mo of age (all P < 0.0001) and declined to very low abundance by 16 mo of age in all depots. Expression of PPARγ and CPT-1β was greater (P < 0.03) in flank, rib, and sirloin subcutaneous adipose tissues than in brisket and round adipose tissues. The expression of the SCD gene did not differ among the 4 age groups (P = 0.95). The palmitoleic:stearic acid ratio (an estimate of SCD activity) was greater (P < 0.001) in the subcutaneous adipose tissues from brisket, plate, and round than in the loin, rib, and sirloin. Conversely, subcutaneous adipose tissue from the loin, rib, and sirloin had greater (P < 0.001) SCD gene expression than the brisket, plate, and round. In general, subcutaneous adipose tissues with the highest concentration of MUFA and least SFA consistently exhibited the least SCD gene expression and adipogenic gene expression. We conclude that MUFA in the brisket and other depots with large SCD indices were deposited before 9 mo of age, during a time when the subcutaneous adipocytes were highly differentiated.</P>
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