The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform
John E. Sani - One of the best experts on this subject based on the ideXlab platform.
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Reliability Assessment of a Solid and Nail-jointed Box-Section African Birch (Anogeissus leiocarpus) Timber Column
ATBU Journal of Science Technology and Education, 2019Co-Authors: Uwemedimo Nyong Wilson, A.a. Adedeji, I S Mohammed, J.a. Alomaja, John E. SaniAbstract:In an attempt to study the performance of a box-section timber column, a structural reliability analysis was carried out on the Nigerian-grown African birch to ascertain its usability for columns under several axial Loads. Samples of the timber were bought, sawn and used to prepare small clear specimens of box columns after which their compressive strengths were obtained. Results of corresponding solid square sections of the same timber specie were used as the control. Some statistical parameters were determined for the deterministic design of the timber column. A FORTRAN-based program was also developed and used for the reliability analysis of the Nigerian-grown African birch columns designed to ascertain their level of safety using First-Order Reliability Method (FORM). From the reliability analysis, both sections were found adequate to support the design Load however, it was found out that only beyond 100kN is there an advantage of the box-section above the solid. The compressive capacity of the box-section (150 x 150mm) was found to be 1.5 times that of the solid section and this margin increases to more than two times the solid section as the design Load was increased to 1000kN. Also, the box section has a higher capacity to bear its Euler Load with a greater length than the solid section because of its greater radius of gyration and rigidity. Therefore the box section would rather be preferable for long columns than the solid section. Lastly, the box-section is also economically advantageous considering the area of the design section- 10,400mm 2 over the solid section offering a cross sectional area of 22,500mm 2 .
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Reliability-Based Design of Solid and Nail-jointed I-Section of Nigerian-Grown African Birch ( Anogeissus leiocarpus ) Timber Column
Journal of Applied Sciences and Environmental Management, 2019Co-Authors: Uwemedimo Nyong Wilson, A.a. Adedeji, J.a. Alomaja, Folagbade Olusoga Peter Oriola, John E. SaniAbstract:The Nigerian-grown African birch timber was used to assemble I- section specimens which were tested in the laboratory for their compressive strengths. Solid square sections of the same specie were similarly tested for an apt comparison of results. A structural reliability analysis was carried out for these two sections to ascertain their performance as structural timber columns using statistical parameters that were determined for the deterministic design of the timber column. A FORTRAN-based program was also developed and used for the reliability analysis of the Nigerian-grown African birch columns designed to ascertain their level of safety using First-Order Reliability Method (FORM). The ‘I’- section was found unsafe to bear the design Load unlike its corresponding solid section. An identified I- section of (100 x 400mm) was found adequate (with Pf =1.22 x 10 -02 ) whose compressive resistance corresponds to (200 x 100mm) of the solid section (with Pf =7.76 x 10 -02 ) which is practically half the dimension of the I-section. This shows that the solid section has a capacity twice that of the ‘I’- section of equal dimensions. However, considering the minimum dimension of the of the two sections capable of supporting the design Load, the ‘I’- section is more economical than the solid section since it offers a less effective area of 11,200mm 2 compared to the solid section with an effective area of 20,000mm 2 . The ‘I’-section also showed a higher capacity to bear the Euler Load with greater lengths than the solid section because of its greater radius of gyration and rigidity value and would be rather preferable for long columns than the solid section. Considering the limited availability of larger dimensions of solid sections, the built-up I- section would be more relevant where large sized sections are required. Keywords : Solid section, Compressive capacity, Built-up sections, Reliability, Probability of failure (Pf)
M.a. Grekov - One of the best experts on this subject based on the ideXlab platform.
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On Symmetrical and Antisymmetrical Buckling of a Plate with Circular Nanohole under Uniaxial Tension
Applied mathematical sciences, 2020Co-Authors: A. O. Bochkarev, M.a. GrekovAbstract:The influence of the surface stress on the local buckling of an infinite plate with a circular nanohole under the uniaxial remote tension is investigated. The critical (Euler) Load corresponding to the buckling is sought by the Ritz method in framework of the linearized Karman set of equations under the symmetrical and antisymmetrical form of the deflection. Numerical calculations are performed for different elastic properties of the surface. It is shown that taking into account the surface stress decreases the critical Load in both cases and the symmetrical form of buckling occurs before the antisymmetrical one.
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The influence of the surface stress on the local buckling of a plate with a circular nanohole
2015 International Conference "Stability and Control Processes" in Memory of V.I. Zubov (SCP), 2015Co-Authors: A. O. Bochkarev, M.a. GrekovAbstract:The influence of the surface stress on the local buckling of an infinite plate with a circular nanohole under the uniaxial remote tension is investigated. The critical (Euler) Load corresponding to the buckling is found with the Ritz method in the framework of the linearized von Karman set of equations. Numerical computations are performed with the Ritz method for various elastic properties of the surface. It is shown that one doesn't get a significant correction of the local buckling (i.e of the critical Load), if residual surface stress is included into the mathematically exact theory of surface elasticity.
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Local instability of a plate with a circular nanohole under uniaxial tension
Doklady Physics, 2014Co-Authors: A. O. Bochkarev, M.a. GrekovAbstract:The problem of the influence of surface tension on the local instability of a plate under tension is investigated by the example of an infinite plate with a circular nanohole. The method for solving the problem under consideration is based on a previously developed approach for solving problems on local buckling of a thin uniaxially stretched elastic sheet with variously shaped macroholes. The critical (Euler) Load, at which the instability occurs, is sought by the Ritz method in framework of the linearized Karman set of equations based on the principle of virtual motions as the smallest positive Load giving the minimum of the potential energy of the plate deformation. The generalized plane stress state of the plate with a nanohole is found for its application taking into account surface stresses. The linearized Gurtin-Murdoch relationships for the surface elasticity, the generalized Young-Laplace law, and the Goursat-Kolosov complex potentials are used when deriving analytical dependences for the stress in this plane problem. The deflection of the plate is represented by a double row satisfying the damping condition at infinity and ensuring freedom of motion of hole edges. Numerical calculations are performed for the aluminum plate. Two variants of the elastic properties of a circular hole are considered. Zones of compressing circumferential tensions near the edges of the circular hole with radii 1, 2, and 4 nm under uniaxial tension are constructed. It is shown that the account of the surface stresses decreases the critical Load, which has a tendency to decrease in both cases with a decrease in the cut radius in a nanometer variation range.
S. Sadiku - One of the best experts on this subject based on the ideXlab platform.
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On the Application of the Perturbation Method in the Buckling Optimization of a Heavy Elastic Column of Constant Aspect Ratio
Journal of Optimization Theory and Applications, 2010Co-Authors: S. SadikuAbstract:This paper addresses the problem of maximizing the first Euler Load of a column of constant aspect ratio (moment of inertia varies with the square of the cross-sectional area), considering the column self-weight, subject to the constraint of fixed volume of column material and height. The coupled nonlinear integro-differential equations of optimality and stability, generated through variational principles, have been solved using the method of parameter perturbation. The optimal column has cross-sectional area that follows a perturbed two-thirds power law; the first Euler Load is up to 87% larger than that of the corresponding column of uniform cross-section having the same volume and height.
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On the Application of the Perturbation Method in the Buckling Optimization of a Heavy Elastic Column of Constant Aspect Ratio
Journal of Optimization Theory and Applications, 2010Co-Authors: S. SadikuAbstract:This paper addresses the problem of maximizing the first Euler Load of a column of constant aspect ratio (moment of inertia varies with the square of the cross-sectional area), considering the column self-weight, subject to the constraint of fixed volume of column material and height. The coupled nonlinear integro-differential equations of optimality and stability, generated through variational principles, have been solved using the method of parameter perturbation. The optimal column has cross-sectional area that follows a perturbed two-thirds power law; the first Euler Load is up to 87% larger than that of the corresponding column of uniform cross-section having the same volume and height.
Uwemedimo Nyong Wilson - One of the best experts on this subject based on the ideXlab platform.
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Reliability Assessment of a Solid and Nail-jointed Box-Section African Birch (Anogeissus leiocarpus) Timber Column
ATBU Journal of Science Technology and Education, 2019Co-Authors: Uwemedimo Nyong Wilson, A.a. Adedeji, I S Mohammed, J.a. Alomaja, John E. SaniAbstract:In an attempt to study the performance of a box-section timber column, a structural reliability analysis was carried out on the Nigerian-grown African birch to ascertain its usability for columns under several axial Loads. Samples of the timber were bought, sawn and used to prepare small clear specimens of box columns after which their compressive strengths were obtained. Results of corresponding solid square sections of the same timber specie were used as the control. Some statistical parameters were determined for the deterministic design of the timber column. A FORTRAN-based program was also developed and used for the reliability analysis of the Nigerian-grown African birch columns designed to ascertain their level of safety using First-Order Reliability Method (FORM). From the reliability analysis, both sections were found adequate to support the design Load however, it was found out that only beyond 100kN is there an advantage of the box-section above the solid. The compressive capacity of the box-section (150 x 150mm) was found to be 1.5 times that of the solid section and this margin increases to more than two times the solid section as the design Load was increased to 1000kN. Also, the box section has a higher capacity to bear its Euler Load with a greater length than the solid section because of its greater radius of gyration and rigidity. Therefore the box section would rather be preferable for long columns than the solid section. Lastly, the box-section is also economically advantageous considering the area of the design section- 10,400mm 2 over the solid section offering a cross sectional area of 22,500mm 2 .
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Reliability-Based Design of Solid and Nail-jointed I-Section of Nigerian-Grown African Birch ( Anogeissus leiocarpus ) Timber Column
Journal of Applied Sciences and Environmental Management, 2019Co-Authors: Uwemedimo Nyong Wilson, A.a. Adedeji, J.a. Alomaja, Folagbade Olusoga Peter Oriola, John E. SaniAbstract:The Nigerian-grown African birch timber was used to assemble I- section specimens which were tested in the laboratory for their compressive strengths. Solid square sections of the same specie were similarly tested for an apt comparison of results. A structural reliability analysis was carried out for these two sections to ascertain their performance as structural timber columns using statistical parameters that were determined for the deterministic design of the timber column. A FORTRAN-based program was also developed and used for the reliability analysis of the Nigerian-grown African birch columns designed to ascertain their level of safety using First-Order Reliability Method (FORM). The ‘I’- section was found unsafe to bear the design Load unlike its corresponding solid section. An identified I- section of (100 x 400mm) was found adequate (with Pf =1.22 x 10 -02 ) whose compressive resistance corresponds to (200 x 100mm) of the solid section (with Pf =7.76 x 10 -02 ) which is practically half the dimension of the I-section. This shows that the solid section has a capacity twice that of the ‘I’- section of equal dimensions. However, considering the minimum dimension of the of the two sections capable of supporting the design Load, the ‘I’- section is more economical than the solid section since it offers a less effective area of 11,200mm 2 compared to the solid section with an effective area of 20,000mm 2 . The ‘I’-section also showed a higher capacity to bear the Euler Load with greater lengths than the solid section because of its greater radius of gyration and rigidity value and would be rather preferable for long columns than the solid section. Considering the limited availability of larger dimensions of solid sections, the built-up I- section would be more relevant where large sized sections are required. Keywords : Solid section, Compressive capacity, Built-up sections, Reliability, Probability of failure (Pf)
Sebastian Uzny - One of the best experts on this subject based on the ideXlab platform.
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on bifurcation Load of a three member slender system with internal crack subjected to Euler s Load
Journal of Theoretical and Applied Mechanics, 2018Co-Authors: Sebastian Uzny, Krzysztof SokolAbstract:The results of numerical simulations presented in this paper are concerned with instability of a three member slender system subjected to Euler Load. The investigated column is built up as a flat frame composed of three rods. In the internal one, the defect is present in form of a crack. The boundary problem has been formulated on the basis of a static criterion of instability. The boundary conditions associated with different types of supports are obtained by proper selection of parameters of the generalized Load. On the basis of these results, the magnitude of bifurcation Load can be determined.
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On bifurcation Load of a three-member slender system with internal crack subjected to Euler’s Load
Journal of Theoretical and Applied Mechanics, 2018Co-Authors: Sebastian Uzny, Krzysztof SokółAbstract:The results of numerical simulations presented in this paper are concerned with instability of a three member slender system subjected to Euler Load. The investigated column is built up as a flat frame composed of three rods. In the internal one, the defect is present in form of a crack. The boundary problem has been formulated on the basis of a static criterion of instability. The boundary conditions associated with different types of supports are obtained by proper selection of parameters of the generalized Load. On the basis of these results, the magnitude of bifurcation Load can be determined.