• Steel and Composite Structures
• /
• v.13 no.3
• /
• pp.295-308
• /
• 2012

This paper experimentally investigated the buckling capacity of built-up steel columns mainly, Cruciform Columns (CC) and Side-to-Side (SS) columns fabricated from two Universal Beam (UB) sections. A series of nine experimental tests comprised of three UB sections, three CC sections and three SS sections with different lengths were tested to failure to measure the ultimate axial capacity of each column section. The lengths used for each category of columns were 1.8, 2.0, and 2.2 m with slenderness ratios ranging from 39-105. The measured buckling loads of the tested specimens were compared with the predicted ultimate axial capacity using Eurocode 3, AISC LRFD, and BS 5959-1. It was observed that the failure modes of the specimens included flexural buckling, local buckling and flexural-torsional buckling. The results showed that the ultimate axial capacity of the tested cruciform and side-by-side columns were higher than the code predicted design values by up to 20%, with AISC LRFD design values being the least conservative and the Eurocode 3 design values being the most conservative. This study has concluded that cruciform column and side-to-side welded flange columns using universal beam sections are efficient built-up sections that have larger ultimate axial load capacity, larger stiffness with saving in the weight of steel used compared to its equivalent universal beam counterpart.

• Structural Engineering and Mechanics
• /
• v.74 no.1
• /
• pp.145-156
• /
• 2020

There are separate merits and demerits to wood and steel. The combination of wood and steel as a compound section is able to improve the properties of both and ultimately increase their final bearing capacity. The composite cross-section made of steel and wood has higher hardness while showing more ductility and the local buckling of steel is delayed or completely prevented. The purpose of this study is to investigate the behavior of composite columns enclosed in wooden logs and the hollow sections of steel that will be examined in a laboratory environment under the axial load to determine the final bearing capacity and sample deformation. In terms of methodology, steel sheet and carbon fiber reinforced polymer sheet (FRP) are tested to construct hollow rectangular sections and reinforce timber. Besides, the method of connecting hollow sections and timber including glue and screw has been also investigated. As a result, timber lumber enclosed with carbon fiber-reinforced polymer sheets in which fibers are horizontally located at 90° are more resistant with better ductility.

• Steel and Composite Structures
• /
• v.1 no.2
• /
• pp.171-185
• /
• 2001

The design of tall buildings has recently provided many challenges to structural engineers. One such challenge is to minimise the cross-sectional dimensions of columns to ensure greater floor space in a building is attainable. This has both an economic and aesthetics benefit in buildings, which require structural engineering solutions. The use of high strength steel in tall buildings has the ability to achieve these benefits as the material provides a higher strength to cross-section ratio. However as the strength of the steel is increased the buckling characteristics become more dominant with slenderness limits for both local and global buckling becoming more significant. To arrest the problems associated with buckling of high strength steel, concrete filling and encasement can be utilised as it has the affect of changing the buckling mode, which increases the strength and stiffness of the member. This paper describes an experimental program undertaken for both encased and concrete filled composite columns, which were designed to be stocky in nature and thus fail by strength alone. The columns were designed to consider the strength in axial compression and were fabricated from high strength steel plate. In addition to the encased and concrete filled columns, unencased columns and hollow columns were also fabricated and tested to act as calibration specimens. A model for the axial strength was suggested and this is shown to compare well with the test results. Finally aspects of further research are addressed in this paper which include considering the effects of slender columns which may fail by global instabilities.

• Structural Engineering and Mechanics
• /
• v.40 no.6
• /
• pp.783-800
• /
• 2011

This paper addresses the finite strip formulations for the stability analysis of viscoelastic composite plates with variable thickness in the transverse direction, which are subjected to in-plane forces. While the finite strip method is fairly well-known in the buckling analysis, hitherto its direct application to the buckling of viscoelastic composite plates with variable thickness has not been investigated. The equations governing the stiffness and the geometry matrices of the composite plate are solved in the time domain using both the higher-order shear deformation theory and the method of effective moduli. These matrices are then assembled so that the global stiffness and geometry matrices of a moderately thick rectangular plate are formed which lead to an eigenvalue problem that is solved to determine the magnitude of critical buckling load for the viscoelastic plate. The accuracy of the proposed model is verified against the results which have been reported elsewhere whilst a comprehensive parametric study is presented to show the effects of viscoelasticity parameters, boundary conditions as well as combined bending and compression loads on the critical buckling load of thin and moderately thick viscoelastic composite plates.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.14 no.2
• /
• pp.1-10
• /
• 2011

Six pine trees (Pinus densiflora S. et Z.) at the Euilimji Lake Park in Jecheon were collected to investigate tree ages, growth decline pattern and the years of death. Tree-ring measurement was carried out using the Lintab with a resolution of 0.01mm. Tree age were 80-176 years. Cross-dating between the tree-ring series of each tree and the local chronology from Worak Mountain resulted that four and two trees died in 1998 and 1999, respectively. Three dead trees had only formed earlywood in the outermost tree ring and the others had incomplete latewood. Therefore, it was proven that the former trees died between spring and early summer, whereas the later ones died during late summer and/or autumn. The simultaneous deaths of trees suggest the insect damage and/or drought may be the crucial reason of the death, but frequent reaction woods, which were formed by leaning stem, and scars formed by physical damage may also contribute to the death.

• International Journal of Aeronautical and Space Sciences
• /
• v.18 no.3
• /
• pp.450-466
• /
• 2017

This paper defines the modified effective membrane stiffness, bending stiffness considering the directionally dependent mechanical properties and mode shape function of a composite lattice rectangular plate, which is assumed to be a Kirchhoff-Love plate. It subsequently presents an approximate method of conducting a buckling analysis of the composite lattice rectangular plate with various boundary conditions under uniform compression using the Ritz method. This method considers the coupled buckling mode as well as the global and local buckling modes. The validity of the present method is verified by comparing the results of the finite element analysis. In addition, this paper performs a parametric analysis to investigate the effects of the design parameters on the critical load and buckling mode shape of the composite lattice rectangular plate based on the present method. The results allow a database to be obtained on the buckling characteristics of composite lattice rectangular plates. Consequently, it is concluded that the present method which facilitates the calculation of the critical load and buckling mode shape according to the design parameters as well as the parametric analysis are very useful not only because of their structural design but also because of the buckling analysis of composite lattice structures.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.2
• /
• pp.240-246
• /
• 2008

It has able to be possible that expression and store visual image from analog to digital without picture quality damaged via improvement of video compression technology. And also, It is possible to broadcasting digital image via transmission of digital image on MPEG-2 standardization. For this reason, the broadcasting business owners have converted broadcasting service from analog to digital. But, local SO(System Operator) has a difficult point which secure HD(High Definition) broadcasting program. In this paper, we designed and implemented Scheduling System for MPEG-2 Digital Broadcasting which gather HD broadcasting program from major broadcasting business owners and broadcast them.

• Geomechanics and Engineering
• /
• v.9 no.6
• /
• pp.729-742
• /
• 2015

The aim of the present work was the study of instability in a loose sand from Les Dunes beach in Ain Beninan, Algeria, where the Boumerdes earthquake occurred in 2003. This earthquake caused significant structural damages and claimed the lives of many people. Damages caused to infrastructures were strongly related to phenomena of liquefaction. The study was based on the results of two drained and six undrained triaxial tests over a local sand collected in a region where liquefaction occurred. All the tests hereby analyzed followed compression stress-paths in monotonic conditions and the specimens were isotropically consolidated, since the objective was to study the instability due to static loading as part of a more general project, which also included cyclic studies. The instability was modeled with the second-order work increment criterion. The definition of the instability line for Les Dunes sand and its relation with yield surfaces allowed the identification of the region of potential instability and helped in the evaluation of the susceptibility of soils to liquefy under undrained conditions and its modeling. The dilatancy rate was studied in the points where instability began. Some mixed tests were also simulated, starting with drained conditions and then changing to undrained conditions at different time steps.

• International journal of steel structures
• /
• v.18 no.4
• /
• pp.1363-1372
• /
• 2018

Recently, there have been studies about the increasing effect on the local plate buckling strength of flat plates when longitudinally stiffened with closed-section ribs and an approximate solution to quantitatively estimate these effects were suggested for flat plates. Since there are few studies to utilize such increasing effect on curved panels and a proper design method is not proposed, thus, this study aims to numerically evaluate such effect due to the rotational stiffness of closed-section ribs on curved panels and to propose an approximate method for estimating the buckling strength. Three-dimensional finite element models were set up using a general structural analysis program ABAQUS and a series of parametric numerical analyses were conducted in order to examine the variation of buckling stresses along with the rotational stiffness of closed-section ribs. By using a methodology that combine the strength increment factor due to the restraining effect by closed-section ribs and the buckling coefficient of the panel curvature, the approximate solutions for the estimation of buckling strength were suggested. The validity of the proposed methods was verified through a comparative study with the numerical analysis results.

• Journal of Electrodiagnosis and Neuromuscular Diseases
• /
• v.20 no.2
• /
• pp.153-158
• /
• 2018

Posterior interosseus (PI) nerve compression is a rare form of compressive neuropathy. It can cause pain along the radial nerve course and weakness of radial nerve innervating muscles without sensory symptoms. A 65-year-old man visited our institution complaining weakness of finger extension and thumb abduction after 2 times of injections at the right elbow in local clinic. The patient's clinical history and physical examination implied an iatrogenic radial nerve injury caused by the injection. The electrophysiologic study revealed of posterior interosseus neuropathy (PIN) with incomplete conduction block. However, the ultrasound study showed that the PI nerve was compressed by an anechoic cyst. The magnetic resonance imaging also confirmed of a ganglion cyst, not a hematoma. After repeated aspirations and a steroid injection, the electrophysiologic study showed recovery of motor weakness. Despite of the clue which implying an iatrogenic injury, clinician should consider other possibilities such as ganglion cysts and ultrasound guided aspiration and steroid injection could be an effective option for conservative management.