• Structural Engineering and Mechanics
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• v.8 no.5
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• pp.465-476
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• 1999

A structural optimization process is presented for arches with varying cross-section. The optimality criteria method is used to develop a recursive relationship for the design variables considering displacement, stresses and minimum depth constraints. The depth at the crown and at the support are taken as design variables first. Then the approach is extended by taking the depth values of each joint as design variable. The curved beam element of constant cross section is used to model the parabolic and circular arches with varying cross section. A number of design examples are presented to demonstrate the application of the method.

• Structural Engineering and Mechanics
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• v.29 no.2
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• pp.203-221
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• 2008

In this paper, we present an idea of the geometry-dependent MITC method. The simple concept is exemplified to improve a 2-node iso-beam (isoparametric beam) finite element of varying section. We first study the behavior of a standard 2-node iso-beam finite element of prismatic section, which has been widely used with reduced integration (or the equivalent MITC method) in order to avoid shear locking. Based on analytical studies on cantilever beams of varying section, we propose the axial strain correction (ASC) scheme and the geometry-dependent tying (GDT) scheme for the 2-node iso-beam element. We numerically analyze varying section beam problems and present the improved performance by using both ASC and GDT schemes.

• Communications of the Korean Mathematical Society
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• v.28 no.1
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• pp.177-181
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• 2013

In this note, we consider a curved tube with varying cross-section formed by rotating open bounded Euclidean domains with respect to a reference curve, and successfully give a lower bound to the threshold of the Laplacian on the tube, subject to Dirichlet boundary conditions on the surface and Neumann conditions at the ends of the tube. This generalizes the corresponding result in [1].

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.401-413
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• 2022

This paper provides a simple method by which to estimate the cross-section stress profiles for nozzles designed according to ASME Code Section III. Further, this method validates the effectiveness of earlier work performed by the authors on standard nozzles. The method requires only the geometric information of the pressure vessel and the attached nozzle. A PWR direct vessel injection nozzle, a PWR outlet nozzle, a PWR inlet nozzle and a BWR recirculation outlet nozzle are selected based on their corresponding specific designs, e.g., a varying nozzle radius, a varying nozzle thickness and an outlet nozzle boss. A cross-section stress profile comparison shows that the estimates are in good agreement with the finite element analysis results. Differences in stress intensity factors calculated in accordance with ASME BPVC Section XI Appendix G are discussed. In addition, a change in the dimensions of an alternate nozzle design relative to the standard values is discussed, focusing on the stress concentration factors of the nozzle inside corner.

• Steel and Composite Structures
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• v.11 no.6
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• pp.489-504
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• 2011

This paper presents a theoretical investigation in free vibration of sigmoid functionally graded beams with variable cross-section by using Bernoulli-Euler beam theory. The mechanical properties are assumed to vary continuously through the thickness of the beam, and obey a two power law of the volume fraction of the constituents. Governing equation is reduced to an ordinary differential equation in spatial coordinate for a family of cross-section geometries with exponentially varying width. Analytical solutions of the vibration of the S-FGM beam are obtained for three different types of boundary conditions associated with simply supported, clamped and free ends. Results show that, all other parameters remaining the same, the natural frequencies of S-FGM beams are always proportional to those of homogeneous isotropic beams. Therefore, one can predict the behaviour of S-FGM beams knowing that of similar homogeneous beams.

• Journal of Ocean Engineering and Technology
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• v.18 no.2
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• pp.46-51
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• 2004

Natural frequencies of the transverse vibration of beams with step change in cross-section are obtained by using the asymptotic closed form solution. This closed form solution is found by using WKB method under the assumption of slowly varying properties, such as mass, cross-section, tension etc., along the beam length. However, this solution is found to be still very accurate even in the case of large variation in cross-section and tension. Therefore, this result can be easily applied to many engineering problems.

• Tunnel and Underground Space
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• v.22 no.5
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• pp.310-320
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• 2012

This paper describes the design and construction of a 2-arch tunnel with varying section. This new design has advantages of 2-arch tunnels, which is rather expensive, but is still economically competitive compared to parallel tunnels. Economic analysis was also conducted. To secure the stability of the varying section tunnel, excavated part was reinforced by tie-bolts and RRS, and 2-arch part was supported by EPS blocks and concrete walls. Stability of the pillar was theoretically analyzed and also examined by numerical simulations for various widths. Displacement monitoring was conducted and results were compared with numerical results. Economic analysis showed reductions in construction cost and period by 11% and 10 months respectively.

• Structural Engineering and Mechanics
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• v.16 no.5
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• pp.597-612
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• 2003

In this paper, multi-story buildings with shear-wall structures and with narrow rectangular plane configuration are modeled as a multi-step flexural-shear plate with varying cross-section for buckling analysis. The governing differential equation of such a plate is established. Using appropriate transformations, the equation is reduced to analytically solvable equations by selecting suitable expressions of the distribution of stiffness. The exact solutions for buckling of such a one-step flexural-shear plate with variable stiffness are derived for several cases. A new exact approach that combines the transfer matrix method and closed from solution of one-step flexural-shear plate with continuously varying stiffness is presented for stability analysis of multi-step non-uniform flexural-shear plate. A numerical example shows that the present methods are easy to implement and efficient.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.724-730
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• 1995

Fixed-gain and variable-gain PID control of tension in the winding section of a simple web transport system were evaluated. An open-loop mathematical model for the web transport system was derived and used for the design of the PID controllers. The winding roll radius is a timevarying parameter in the model. The fixed-gain PID controller designed at a particular instant of time could not meet the desired specifications, whereas the variable-gain PID controller could produce accurate tension control in the winding section. An advantage of the variable-gain control is its simplicity. This approach is easy to implement and shows promise for applications where the time-varying parameters are easily measured.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.5
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• pp.453-462
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• 2009

The differential quadrature method(DQM) is applied to the free in-plane vibration analysis of circular curved beams with varying cross-section neglecting transverse shearing deformation. Natural frequencies are calculated for the beams with various opening angles and end conditions. Results obtained by the DQM are compared with available results by other methods in the literature. It is found that the DQM gives good accuracy even with a small number of grid points. In addition, the corrected results are given for the beams not previously presented for this problem.