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Volume 6 (3); 25 May, 2016


altResearch Paper

Buckling Analysis of Biaxially Compressed All-Round Simply Supported (SSSS) Thin Rectangular Isotropicplates using the Galerkin’s Method.

Onwuka, D.O., Ibearugbulem, O.M., Iwuoha, S.E., Arimanwa, J.I., Sule, S.

J. Civil Eng. Urban., 6(3): 48-53, 2016; pii:S225204301600006-6

Abstract

This work studied the buckling analysis of biaxially compressed all-round simply supported (SSSS) thin rectangular isotropic plates using the Galerkin’s method. The study was limited to thin rectangular isotropic plates having aspect ratios ranging from 1 to 2. The general equation for the critical buckling load of a biaxially loaded plate, was formulated from the overall governing differential equation for plates, using the Galerkin’s method. The derived general equation, was expressed as the load in the x-axis in terms of that in the y-axis. This was done by means of a linear relationship which was obtained for the buckling load on the y- axis in terms of that on the x-axis. The SSSS plate deflection equation, was obtained using the polynomial series, and was substituted into the general equation of the critical buckling load of a biaxially loaded plate. This yielded the unique expression for the critical buckling load of a biaxially loaded SSSS plate. Different values (0 to 2) of aspect ratios and “k” (relationship constant between forces on the Y-axis and forces on the X-axis) values (0.1 to 1) were substituted into the critical buckling equation for an SSSS plate, and the critical buckling load coefficients were obtained. The critical buckling load coefficient of a square plate (i.e. at k equal to 1), was obtained as 19.754. When compared with the exact value (19.744) obtained by other researchers who used the trigonometric series, a percentage difference of 0.047 was discovered. At k equal to zero, and for different aspect ratios, the results of the present study showed a maximum percentage difference of 0.069 with those given in the literature. It was therefore concluded that this paper has provided the critical buckling load equation, and results for a biaxially loaded SSSS plates having different k values and aspect ratios, whose result has not been found in the literature.
Keywords: Buckling Analysis, Plates, Biaxial Forces, Galerkin’s Method, Boundary Condition.

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altResearch Paper

Variations of Flow Separation Zone at Lateral Intakes Entrance using Submerged Vanes.

Jamshidi A, Farsadizadeh D, Hosseinzadeh Dalir A.

J. Civil Eng. Urban., 6(3): 54-63, 2016; pii:S225204301600007-6

Abstract

Flow Separation in the upstream of the intake channel is a critical issue causing eddy flow into the intake entrance. It reduces the intake efficiency and the effective width of flow in intake. Therefore, it is essential to identify the dimensions of the flow separation zone. Installation of submerged vanes in intake entrance is a method which is usually applied to reduce the size of flow separation zone. In this study the dimensions of flow separation zone were measured in presence of submerged vanes with five arrangements including parallel, stagger, compound, piney and butterflies (the piney and butterflies models were provided for the first time that is our innovation in present paper ) by four discharges of 15, 20, 25 and 30 L/s in main channel entrance. Multivariate regression equations were extracted for investigated flow separation zone using SPSS software. R2 of these equations changes from 0.87 to 0.96, which statistically, can be considered as valid equations in hydraulic flow studies at lateral intake entrance. These results are also comparable with other studies which all of them show a reducing of the size of flow separation zone with increasing ratio of lateral intake discharge. Piney submerged vanes were selected as the best model that reduced the size of flow separation zone and made proper flow profile in main channel and intake entrance. Comparing with pilot model tests, this model reduced the length and width of flow separation zone 36.34%, 32.53%, 34.37%, 30.72% and 27.46%, 31% , 31.33 % , 30% respectively at four different discharges of 15, 20, 25 and 30 L/s. Results showed that the ratio of width to length of separation zone (shape index of zone) was between two values 0.2 and 0.28 in the all models.
Key words: Intake channel, Flow separation zone, Submerged vanes, Shape index of zone, Piney model.

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