• Structural Engineering and Mechanics
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• v.36 no.6
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• pp.729-744
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• 2010

There is world wide concern for safety of nuclear power installations after the terrorist attack on World Trade Center in 2001 and several other civilian structures in the last decade. The nuclear containment structure in many countries is a double shell structure (outer shell a RCC and inner a prestressed concrete). The outer reinforced concrete shell protects the inner shell and is designed for external loading like impact and blast. A comparative study of non-linear response of reinforced concrete nuclear containment cylindrical shell subjected to impact of an aircraft (Phantom) and explosion of different amounts of blast charges have been presented here. A material model which takes into account the strain rate sensitivity in dynamic loading situations, plastic and visco-plastic behavior in three dimensional stress state and cracking in tension has been developed earlier and implemented into a finite element code which has been validated with published literature. The analysis has been made using the developed software. Significant conclusions have been drawn for dissimilarity in response (deflections, stresses, cracks etc.) of the shell for impact and blast loading.

• Journal of Welding and Joining
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• v.17 no.2
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• pp.91-96
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• 1999

The problems of welding distortion in a welded structures are major concern in heavy industry. Weld-induced angular distortion's formula, composed weld parameter such as heat input and plate thickness, is developed analytically by the use of an elliptic cylindrical inclusion with an eigenstrain in an infinite laminated plate theory. The source of angular distortion in weldments is the plastic strains, which are caused by non-uniform temperature gradient. The distributions of the plastic strain corresponding eigenstrain are assumed by the use of Rosenthal's solution expressing thermal history. Comparison of calculated results with experimental data shows the accuracy and validity of the proposed method.

• Steel and Composite Structures
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• v.36 no.1
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• pp.63-74
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• 2020

The present research investigates post-buckling behavior of geometrically imperfect tapered curved micro-panels made of graphene oxide powder (GOP) reinforced composite. Micro-scale effects on the panel structure have been included based on strain gradient elasticity. Micro-panel is considered to be tapered based on thickness variation along longitudinal direction. Weight fractions of uniformly and linearly distributed GOPs are included in material properties based on Halpin-Tsai homogenization scheme considering. Post-buckling curves have been determined based on both perfect and imperfect micro-panel assumptions. It is found that post-buckling curves are varying with the changes of GOPs weight fraction, geometric imperfection, GOP distribution type, variable thickness parameters, panel curvature radius and strain gradient.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.239-243
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• 2012

This paper is concerned with turbulent flow computations using Large Eddy Simulation (LES) and the flow interaction of vortex shedding in a cylindrical duct flow driven by mass blowing through the wall. The purpose is to analyze non-linear combustion characteristics in the presence of vortex shedding generated in a hybrid rocket motor. Experimental studies have shown sudden changes in pressure (referred as a DC-shift), which depend on the strength of vortex strength of incoming flow. The combustion instability because of a sudden change in pressure fluctuations is mainly related with the interaction between vortex shedding. Therefore LES computation on a duct with injected normal blowing was performed to simulate the turbulent flow interactions with the behaviors of vortices and vortex structures along the injected wall.

• Wind and Structures
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• v.1 no.1
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• pp.59-66
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• 1998

The vibrations of bodies subjected to fluid flow can cause modifications in the flow conditions, giving rise to interaction forces that depend primarily on displacements and velocities of the body in question. In this paper the linearized equations of motion for bodies of arbitrary prismatic or cylindrical cross-section in two-dimensional cross-flow are presented, considering the three degrees of freedom of the body cross-section. By restraining the rotational motion, equations applicable to circular tubes, pipes or cables are obtained. These equations can be used to determine stability limits for such structural systems when subjected to non uniform cross-flow, or to evaluate, under the quasi static assumption, their response to vortex or turbulent excitation. As a simple illustration, the stability of a pipe subjected to a bidimensional flow in the direction normal to the pipe axis is examined. It is shown that the approach is extremely powerful, allowing the evaluation of fluid-structure interaction in unidimensional structural systems, such as straight or curved pipes, cables, etc, by means of either a combined experimental-numerical scheme or through purely numerical methods.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.4
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• pp.452-459
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• 2019

In order to design and manufacture structures such as a guided missile, assembly process with fastener is an essential method of fabrication. In this study, the dynamic characteristics of a cylindrical structure with bolted joints were studied using experimental methods. The change of the natural frequency of the structure with the change of the fastening method and the tightening torque were measured by the test and the finite element analysis was performed using the stiffness model of the fastening part according to the fastening method and compared with the test results.

• International journal of steel structures
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• v.18 no.4
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• pp.1318-1324
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• 2018

This paper evaluates the effects of door opening, collar stiffener, and initial imperfection on the ultimate strength of a 10 MW wind tower. The lower segment of the tower was modeled to investigate the ultimate strength using steel cylindrical shell elements of finite element program ABAQUS. The wind tower was classified into three categories; without opening nor stiffener (C1), with opening but no stiffener (C2), and with opening and stiffener (C3). The C2 and C3 were further divided into long axis and short axis categories depending on the position of the opening. Result from linear and nonlinear analyses shows that the bigger the opening the bigger the reduction in strength and the same thing goes for the initial imperfection ratio or ovality of the shell. Also, there is a significant decreased in strength as the initial imperfection ratio increases by as high as 18.08%.

• Structural Engineering and Mechanics
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• v.83 no.5
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• pp.681-692
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• 2022

The vibrational response of the two bones in a Volleyball player's arm under ball impact is conducted. The two bones in hand, Ulna and Radius, are modeled as two cylindrical shells. The formulations associated with the shells' vibration are obtained using the energy method. Then, the results are extracted with the aid of the two-dimensional form of DQM in conjunction with Runge-Kutta. The results are validated by means of a published paper. Lastly, the role of parameters in determining vibrational frequency as well as deflection is explored through parametric studies. It was shown that the impactor speed and the time of the impact could be essential factors in determining the vibration behavior of the bones. This work can be used in the further investigation of the behavior of bones and physiological structures.

• Advances in concrete construction
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• v.15 no.1
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• pp.47-61
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• 2023

This paper examines the dynamic response of rotating nanodevices under the external harmonic load. The spinning nanosystem is made of nanoscale tubes that rotate around the central nanomotor and is mathematically modeled via high-order beam theory as well as nonclassical nonlocal theory for the size impact. According to the Hamilton principle, the dynamic motion equations are derived, then the time-dependent results are obtained using the Newmark Beta technique along with the generalized differential quadratic method. The presented results are discussed dynamic deflection, resonant frequency, and natural frequency in response to the different applicable parameters, which help develop and produce nanoelectromechanical systems (NEMS) for various applications.

• Steel and Composite Structures
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• v.51 no.4
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• pp.377-389
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• 2024

In the present study, thermoelsatoplastic stresses and displacement for rotating hollow disks made of functionally graded materials (FGMs) has been investigated. The linear elastic-fully plastic condition is considered. The material properties except Poisson's ratio are assumed to vary in the radial direction as a power-law function. The heat conduction equation for the one-dimensional problem in cylindrical coordinates is used to obtain temperature distribution in the disk. The plastic model is based on the Tresca yield criterion and its associated flow rules under the assumption of perfectly plastic material behavior. Exact solutions of field equations for elastic and plastic deformations are obtained. It is shown that the elastoplastic response of the functionally graded (FG) disk is affected notably by the radial variation of material properties. It is also shown that, depending on material properties and disk dimensions, different modes of plastic deformation may occur.