scholarly journals Buckling Analysis of Piles in Multi-Layered Soils

2021 ◽  
Vol 11 (22) ◽  
pp. 10624
Author(s):  
Luigi Fenu ◽  
Eleonora Congiu ◽  
Mariangela Deligia ◽  
Gian Felice Giaccu ◽  
Alireza Hosseini ◽  
...  
Keyword(s):  
Fourier Series ◽  
Direct Method ◽  
Buckling Analysis ◽  
Layered Soil ◽  
Buckling Load ◽  
Layered Soils ◽  
Minimum Eigenvalue ◽  
Element Analysis ◽  
Pile Deformation ◽  
Stiffness Distribution

Pile buckling is infrequent, but sometimes it can occur in slender piles (i.e., micropiles) driven into soils with soft layers and/or voids. Buckling analysis of piles becomes more complex if the pile is surrounded by multi-layered soil. In this case, the well-known Timoshenko’s solution for pile buckling is of no use because it refers to single-layered soils. A variational approach for buckling analysis of piles in multi-layered soils is herein proposed. The proposed method allows for the estimation of the critical buckling load of piles in any multi-layered soil and for any boundary condition, provided that the distribution of the soil coefficient of the subgrade reaction is available. An eigenvalue-eigenvector problem is defined, where each eigenvector is the set of coefficients of a Fourier series describing the second-order displaced shape of the pile, and the related buckling load is the eigenvalue, thus obtaining the effective buckling load as the minimum eigenvalue. Besides the pile deformed shape, the stiffness distribution in the multi-layered soil is also described through a Fourier series. The Rayleigh–Ritz direct method is used to identify the Fourier development coefficients describing the pile deformation. For validation, buckling analysis results were compared with those obtained from an experimental test and a finite element analysis available in the literature, which confirmed this method’s reliability.

Buckling Analysis of Hollow Microneedle in Transdermal Drug Delivery

2016 ◽  
Author(s):  
N. Raja Rajeswari ◽  
P. Malliga ◽  
B. K. Gnanavel
Keyword(s):  
Drug Delivery ◽  
Transdermal Drug Delivery ◽  
Reaction Force ◽  
Vital Role ◽  
Buckling Analysis ◽  
Buckling Load ◽  
Insertion Force ◽  
Element Analysis ◽  
Critical Buckling Load ◽  
Hollow Microneedle

In biomedical field, the microneedles have gained popularity in the transdermal drug delivery applications. A hollow out-of-plane microneedle with bevel shaped tip, made up of silicon material is considered in this paper. The safe insertion of such microneedles into the soft tissue without breakage plays a vital role in the design of microneedles. The primary mode of failure often found in microneedles is buckling. When the microneedle is applied with an insertion force (F) larger than the critical buckling load (Pcr), it may suffer from buckling. In this paper, the buckling analysis of silicon microneedle is performed using Finite Element Analysis. The equilibrium equation of Love’s (1944) thin rod theory is used to study the buckling effect of microneedle. A non-linear Eigen value buckling analysis of the hollow microneedle is performed. The fundamental mode 1 and the critical mode 813 are discussed. The deflection, stresses and reaction force are analysed for both the modes. The critical buckling load (Pcr) is determined to be 0.39 N and if the microneedle is applied with insertion force within this value of critical buckling load, it avoids buckling. Therefore, this critical buckling load is taken as a conservative result for designing the microneedle.

scholarly journals Buckling analysis of Functionally Graded Natural Fiber-Flyash-Epoxy (FGNFFE) Cylinder

2019 ◽  
Vol 8 (6) ◽  
pp. 4260-4265
Keyword(s):  
Hollow Cylinder ◽  
Natural Fiber ◽  
Buckling Analysis ◽  
Functionally Graded ◽  
Buckling Load ◽  
Common Element ◽  
Element Analysis ◽  
Modern Material ◽  
Critical Buckling Load ◽  
Structural Applications

A hollow cylinder or a pipe is a common element used in structural applications. Now days in the era of new material development, replacement of consventional materials by modern material are of primary choice for the researchers and developers as well. This paper presents the bucking analysis of functionally graded natural-fiber-flyash-epoxy (FGNFFE) hollow cylinders using FEA. In the first part, a mathematical model for buckling analysis is developed to get the dynamic behavior of hollow cylinder under free vibration. Initial five modes of buckling analysis are performed by theoretical, finite element analysis and experimentation. Accordingly Mechanical properties are obtained and used for buckling study in FEA environment as being a cylindrical structure to the design, it is subjected to compression and buckling due to self weight and due to external load is very common. The critical buckling load is determined by FEA study and compared with the experimental value. Further the study extended by optimizing the critical buckling load and stress with respect to the ingredients and other designed parameters and discussed.

scholarly journals Assessment of the global stability of three-limbed steel tube latticed column using finite element modelling

2021 ◽  
Vol 2045 (1) ◽  
pp. 012021
Author(s):  
Y D Fu ◽  
X Y Dai ◽  
H D Zhang ◽  
K G Shang
Keyword(s):  
Finite Element ◽  
Global Stability ◽  
Steel Tube ◽  
Buckling Analysis ◽  
Buckling Load ◽  
Elastic Buckling ◽  
Analysis Method ◽  
Element Analysis ◽  
Stability Performance ◽  
Geometric Defect

Abstract In order to study the stability performance of the three-limbed steel tube latticed column, the finite element numerical analysis method based on the structural stability theory is adopted. Firstly, the linear analysis of the three-limbed steel tube latticed column without diagonal lacing bar is carried out, and the calculation method of elastic buckling load considering the influence of shear deformation is obtained. Then, the elastic buckling analysis and elastoplastic buckling analysis three-limbed steel tube latticed column with diagonal lacing bar are carried out. The elastic buckling load and elastoplastic buckling load of three-limbed steel tube latticed column with diagonal lacing bar are studied when only the global initial geometric defects, only the member initial geometric defects, and both kinds of defects are considered at the same time. The results show that the direct finite element analysis method can be used to calculate the elastic buckling load of three-limbed steel tube latticed column with diagonal lacing bar, and the error is 6.67%. In the elastic analysis of three-limbed steel tube latticed column with diagonal lacing bar, the column global stability mainly depends on the global initial geometric defects, and the member initial geometric defect is negligible. And when two kinds of defects are applied at the same time, the structural buckling load is reduced by less than 0.20% compared to the global initial geometric defects. In the elastoplastic analysis, the column global stability is determined by both the global initial geometric defect and the member initial geometric defect. When both defects are applied at the same time, the structural buckling load decreases by less than 0.65% compared to the global initial geometric defect only, and 7.60% compared to the member initial geometric defects only. It can be concluded that there is little difference in the overall stability bearing capacity between the two kinds of defects.

Buckling characteristics of cut-out borne composite stiffened hyperbolic paraboloid shell panel

2021 ◽  
pp. 146442072110058
Author(s):  
Sarmila Sahoo
Keyword(s):  
Finite Element ◽  
Orientation Angle ◽  
Buckling Load ◽  
Benchmark Problems ◽  
Hyperbolic Paraboloid ◽  
Element Analysis ◽  
Load Effect ◽  
Global Buckling ◽  
Fiber Orientation Angle ◽  
Shell Panel

The present study investigates buckling characteristics of cut-out borne stiffened hyperbolic paraboloid shell panel made of laminated composites using finite element analysis to evaluate the governing differential equations of global buckling of the structure. The finite element code is validated by solving benchmark problems from literature. Different parametric variations are studied to find the optimum panel buckling load. Laminations, boundary conditions, depth of stiffener and arrangement of stiffeners are found to influence the panel buckling load. Effect of different parameters like cut-out size, shell width to thickness ratio, degree of orthotropy and fiber orientation angle of the composite layers on buckling load are also studied. Parametric and comparative studies are conducted to analyze the buckling strength of composite hyperbolic paraboloid shell panel with cut-out.

RELIABILITY ASSESSMENT OF AXIALLY COMPRESSED COMPOSITE CYLINDRICAL SHELLS WITH RANDOM IMPERFECTIONS

2011 ◽  
Vol 11 (02) ◽  
pp. 215-236 ◽  
Author(s):  
MATTEO BROGGI ◽  
ADRIANO CALVI ◽  
GERHART I. SCHUËLLER
Keyword(s):  
Mathematical Models ◽  
Axial Compression ◽  
Cylindrical Shells ◽  
Reliability Assessment ◽  
Buckling Analysis ◽  
Buckling Load ◽  
Experimental Results ◽  
Drastic Decrease ◽  
Different Types ◽  
Probability And Statistics

Cylindrical shells under axial compression are susceptible to buckling and hence require the development of enhanced underlying mathematical models in order to accurately predict the buckling load. Imperfections of the geometry of the cylinders may cause a drastic decrease of the buckling load and give rise to the need of advanced techniques in order to consider these imperfections in a buckling analysis. A deterministic buckling analysis is based on the use of the so-called knockdown factors, which specifies the reduction of the buckling load of the perfect shell in order to account for the inherent uncertainties in the geometry. In this paper, it is shown that these knockdown factors are overly conservative and that the fields of probability and statistics provide a mathematical vehicle for realistically modeling the imperfections. Furthermore, the influence of different types of imperfection on the buckling load are examined and validated with experimental results.

An Exact Three-Dimensional Beam Element With Nonuniform Cross Section

2010 ◽  
Vol 77 (6) ◽  
Author(s):  
M. Jafari ◽  
M. J. Mahjoob
Keyword(s):  
Cross Section ◽  
Stiffness Matrix ◽  
Degrees Of Freedom ◽  
Direct Method ◽  
Three Dimensional ◽  
Curved Beams ◽  
Element Analysis ◽  
Shear Loads ◽  
Line Passing ◽  
Exact Stiffness Matrix

In this paper, the exact stiffness matrix of curved beams with nonuniform cross section is derived using direct method. The considered element has two nodes and 12 degrees of freedom, with three forces and three moments applied at each node. The noncoincidence effect of shear center and center of area is also considered in this element. The deformations of the beam are due to bending, torsion, tensile, and shear loads. The line passing through center of area is a general three-dimensional curve and the cross section properties may change arbitrarily along it. The method is extended to deal with distributed loads on the curved beams. The stiffness matrix of some selected types of beams is determined by this method. The results are compared (where possible) with previously published results, simple beam finite element analysis and analytic solution. It is shown that the determined stiffness matrix is exact and that any type of beam can be analyzed by this method.

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