• Journal of the Korea Convergence Society
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• v.10 no.4
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• pp.139-145
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• 2019

This paper investigated the strength and stiffness of composite truss unit structures. The model used is a core-filled model combining the Kagome model and the cube truss model. The material properties used for the analysis are 304 stainless steel with elastic modulus of 193 GPa and yield stress of 215 MPa. The theoretical equation is derived from the relative elasticity relation of Gibson - Ashby ratio, the analysis was performed using Deform 3D, a commercial tool. In conclusion, the relative elasticity for this unit model correlates with 1.25 times the relative density and constant coefficient, elasticity is inversely proportional to pore size. The relative compressive strength has a correlation with relative density of 1.25 times. Proof of this is a real experiment, the derived theoretical relationship should further consider mechanical behavior such as bending and buckling. In the future, it is hoped that the research on the elasticity and the stress according to the structure of the three-dimensional space will be continued.

• Advances in nano research
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• v.16 no.5
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• pp.509-519
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• 2024

In this study, the static analysis of carbon nanotube-reinforced composites (CNTRC) beams resting on a Winkler-Pasternak elastic foundation is presented. The developed theories account for higher-order variation of transverse shear strain through the depth of the beam and satisfy the stress-free boundary conditions on the top and bottom surfaces of the beam. To study the effect of carbon nanotubes distribution in functionally graded (FG-CNT), we introduce in the equation of CNT volume fraction a new exponent equation. The SWCNTs are assumed to be aligned and distributed in the polymeric matrix with different patterns of reinforcement. The rule of mixture is used to describe the material properties of the CNTRC beams. The governing equations were derived by employing Hamilton's principle. The models presented in this work are numerically provided to verify the accuracy of the present theory. The analytical solutions are presented, and the obtained results are compared with the existing solutions to verify the validity of the developed theories. Many parameters are investigated, such as the Pasternak shear modulus parameter, the Winkler modulus parameter, the volume fraction, and the order of the exponent in the volume fraction equation. New results obtained from bending and stresses are presented and discussed in detail. From the obtained results, it became clear the influence of the exponential CNTs distribution and Winkler-Pasternak model improved the mechanical properties of the CNTRC beams.

• Steel and Composite Structures
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• v.17 no.4
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• pp.471-495
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• 2014

The responses of steel buildings with perimeter moment resisting frames (PMRF) with medium size columns (W14) are estimated and compared with those of buildings with deep columns (W27), which are selected according to two criteria: equivalent resistance and equivalent weight. It is shown that buildings with W27 columns have no problems of lateral torsional, local or shear buckling in panel zone. Whether the response is larger for W14 or W27 columns, depends on the level of deformation, the response parameter and the structural modeling under consideration. Modeling buildings as two-dimensional structures result in an overestimation of the response. For multiple response parameters, the W14 columns produce larger responses for elastic behavior. The axial load on columns may be significantly larger for the buildings with W14 columns. The interstory displacements are always larger for W14 columns, particularly for equivalent weight and plane models, implying that using deep columns helps to reduce interstory displacements. This is particularly important for tall buildings where the design is usually controlled by the drift limit state. The interstory shears in interior gravity frames (GF) are significantly reduced when deep columns are used. This helps to counteract the no conservative effect that results in design practice, when lateral seismic loads are not considered in GF of steel buildings with PMRF. Thus, the behavior of steel buildings with deep columns, in general, may be superior to that of buildings with medium columns, using less weight and representing, therefore, a lower cost.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.653-660
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• 2004

To increase the efficiency of the urban areas, pipe section steel piers, which have relatively small sections, must be constructed. Since smaller sections mean decreased load capacity, longitudinal stiffeners were applied to the pipe section steel piers to increase their load capacity. Increased load capacity through longitudinal stiffeners, however, could not yet be confirmed. Therefore, the effect of longitudinal stiffeners on the load capacity of pipe section steel piers still needs to be studied. In this paper, the effect of the number of longitudinal stiffeners on the load capacity of steel piers was determined by carrying out elastic plastic FE analysis on material and geometric non-linearity. In addition, comparative analyses of the parameters of the width, the thickness of longitudinal stiffeners, and the slenderness ratio of steel piers were carried out to determine the effects of longitudinal stiffeners.

• Advances in aircraft and spacecraft science
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• v.6 no.2
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• pp.117-144
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• 2019

High Altitude and Long Endurance (HALE) aircraft are capable of providing intelligence, surveillance and reconnaissance (ISR) capabilities over vast geographic areas when equipped with advanced sensor packages. As their use becomes more widespread, the demand for additional range, endurance and payload capability will increase and designers are exploring non-conventional configurations to meet the increasing demands. One such configuration is the joined-wing concept. A joined-wing aircraft is one that typically connects a front and aft wings in a diamond shaped planform. One such example is the Boeing SensorCraft configuration. While the joined-wing configuration offers potential benefits regarding aerodynamic efficiency, structural weight, and sensing capabilities, structural design requires careful consideration of elastic buckling resulting from the aft wing supporting, in compression, part of the forward wing structural loading. It has been shown already that this is a nonlinear phenomenon, involving geometric nonlinearities and follower forces that tend to flatten the entire configuration, leading to structural overload due to the loss of the aft wing's ability to support the forward wing load. Severe gusts are likely to be the critical design condition, with flight control system interaction in the form of Gust Load Alleviation (GLA) playing a key role in minimizing the structural loads. The University of Victoria Center for Aerospace Research (UVic-CfAR) has built a 3-meter span scaled and flexible wing UAV based on the Boeing SensorCraft design. The goal is to validate the nonlinear structural behavior in flight. The main objective of this research work is to perform Ground Vibration Tests (GVT) to characterize the dynamic properties of the scaled flight vehicle. Results from the experimental tests are used to characterize the modal dynamics of the aircraft, and to validate the numerical models. The GVT results are an important step towards a safe flight test program.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.727-734
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• 2006

Although a limited number of experimental investigations and finite element analyses revealed that a curved web panel in practical design has a considerable reserve strength after the elastic buckling as a straight girder web panel, the current Guide Specifications for Horizontally Curved Steel Girder Highway Bridges (AASHTO, 2003) do not consider the postbuckling strength in the ultimate shear strength due to lack of a comprehensive study. In this study, the ultimate shear strength behavior of horizontally curved steel web panels was investigated through nonlinear finite element analysis and experimental test. It was found that curved web panels used in practical designs are able to develop the postbuckling strength that is equivalent to that of straight girder web panels having the same dimensional and material properties.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.429-438
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• 2011

In this study, the explicit numerical algorithm was proposed to simulate the stress erection process and ultimate-load analysis of the strarch (stressed arch) system. The strarch system is a unique and innovative structural system and member prestress comprising prefabricated plane truss frames erected through a post-tensioning stress erection procedure. The flexible bottom chord, which has sleeve and gap details, is closed by the reaction force of the prestressing tendon. The prestress imposed on the tendon will enable the strarch system to be erected. This post-tensioning process is called "stress erection process." During this process, plastic rigid-body rotation occurs to the flexible top chord due to the excessive amount of plastic strain, and the structural characteristic is unstable. In this study, the dynamic relaxation method (DRM) was adopted to calculate the nonlinear equilibrium equation of the system, and a displacement-based finite-element-formulated filament beam element was used to simulate the nonlinear behavior of the top chord sections of the strarch system. The section of the filament beam element was composed by the amount of filaments, which can be modeled by various material models. The Ramberg-Osgood and bilinear kinematic elastic plastic material models were formulated for the nonlinear material behaviors of the filaments. The numerical results that were obtained in the present study were compared with the experiment results of the stress erection and with the results of the ultimate-load analysis of the strarch unit frame. The results of the present studies are in good agreement with the previous experiment results, and the explicit DRM enabled the analysis of the post-buckling behaviors of the strarch unit frame.

• Bulletin of the Society of Naval Architects of Korea
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• v.25 no.4
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• pp.69-80
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• 1988

This paper proposes simple formulae for buckling and ultimate strength estimation of plates subjected to water pressure and uniaxial compression. For the construction of a formula for elastic buckling strength estimation, parametric study for actual ship plates with varying aspect ratios and the magnitude of water pressure is carried out by means of principle of minimum potential energy. Based on the results by parametric study, a new formula is approximately expressed as a continuous function of loads and aspect ratio. On the other hand, in order to get a formula for ultimate strength estimation, in-plane stress distribution of plates is investigated through large deflection analysis and total in-plane stresses are expressed as an explicit form. By applying Mises's plasticity condition, ultimate strength criterion is then derives. In the case of plates under relatively small water pressure, the results by the proposed formulae are in good agreement compared with those by other methods and experiment. But present formula overestimates the ultimate strength in the range of large water pressure. However, actual ship plates are subjected to relatively small water pressure except for the impact load due to slamming etc.. Therefore, it is considered that present formulae can be applied for the practical use.

• Steel and Composite Structures
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• v.34 no.1
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• pp.1-15
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• 2020

This paper presents experimental and numerical studies on effects of local damages on the in-plane elastic-plastic buckling and strength of a fixed parabolic steel tubular arch under a vertical load distributed uniformly over its span, which have not been reported in the literature hitherto. The in-plane structural behaviour and strength of ten specimens with different local damages are investigated experimentally. A finite element (FE) model for damaged steel tubular arches is established and is validated by the test results. The FE model is then used to conduct parametric studies on effects of the damage location, depth and length on the strength of steel arches. The experimental results and FE parametric studies show that effects of damages at the arch end on the strength of the arch are more significant than those of damages at other locations of the arch, and that effects of the damage depth on the strength of arches are most significant among those of the damage length. It is also found that the failure modes of a damaged steel tubular arch are much related to its initial geometric imperfections. The experimental results and extensive FE results show that when the effective cross-section considering local damages is used in calculating the modified slenderness of arches, the column bucking curve b in GB50017 or Eurocode3 can be used for assessing the remaining in-plane strength of locally damaged parabolic steel tubular arches under uniform compression. Furthermore, a useful interaction equation for assessing the remaining in-plane strength of damaged steel tubular arches that are subjected to the combined bending and axial compression is also proposed based on the validated FE models. It is shown that the proposed interaction equation can provide lower bound assessments for the remaining strength of damaged arches under in-plane general loading.