• Journal of Korean Association for Spatial Structures
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• v.3 no.1 s.7
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• pp.69-75
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• 2003

This paper is represented a general equations to obtain the elastic local buckling stresses for the flange and web of H-beam under compression at elevated temperatures and is also developed the software to perform the elastic local buckling analysis at elevated temperatures. Eurocode3 Part 1.2 are used to analyse the decrease in steel yield strength and elastic modulus at elevated temperatures. For design examples of 6 H-beams, the elastic local buckling stresses and critical temperatures for the slenderness ratio $(b/t_f\;and\;d/t_w)$ of the flange and web under uniform compression at elevated temperatures have been analysed by a computer program of this paper. It can be seen that the computer analytical results of this study show a good agreement with the experimental results by Wadee.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.4
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• pp.56-62
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• 2004

Using NC or CNC machine tool, the unmanned automatic production system has been growing recently in the manufacturing field. Thus it is important to find out the machinability of cutting force, tool wear and surface roughness during the cutting process. It is necessary to find how to estimate the machinability for the effective cutting condition because of problem about cutting power, tool wear, cutting time and precision. This study was planned to discover the relations of tool wear by variations of roughness and derived to correlate the wear with the surface roughness on the cutting parameter(cutting force, flank wear, surface roughness, friction angle, shear angle, slenderness ratio) when the aluminum alloy was cut in turning.

• Structural Engineering and Mechanics
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• v.6 no.2
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• pp.161-172
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• 1998

Reinforced concrete beams possess variable flexural and torsional stiffnesses due to formation of cracks in the tension area along the beam. In order to check the stability of the beam, it is thus more appropriate to divide the beam into a finite number of segments for which mean stiffnesses and also bending moments are calculated. The stability analysis is further simplified, by using these mean values for each segment. In this paper, an algorithm for calculating the critical lateral buckling slenderness ratio for a definite load level, in a reinforced concrete beam without lateral support at the flanges, is presented. By using this ratio, the lateral buckling safety level of a slender beam may be checked or estimated.

• Structural Engineering and Mechanics
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• v.36 no.1
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• pp.1-18
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• 2010

A total of 28 wall panels were cast and tested under uniformly distributed axial load in one-way in-plane action to study the effect of slenderness ratio (SR) and aspect ratio (AR) on the ultimate load. Two concrete formulations, normal concrete (NC) and self compacting concrete (SCC), were used for the casting of wall panels. Out of 28 wall panels, 12 were made of NC and the remaining 16 panels were of SCC. All the 12 NC panels and 12 out of 16 SCC panels were used to study the influence of SR and the remaining 4 SCC panels were tested to study the effect of AR on the ultimate load. A brief review of studies available in literature on the strength and behaviour of reinforced concrete (RC) wall panels is presented. Load-deformation response was recorded and analyzed. The ultimate load of SCC wall panels decreases non-linearly with the increase in SR and decreases linearly with increasing values of AR. Based on this study a method is proposed to predict the ultimate load of reinforced SCC wall panels. The modified method includes the effect of SR, AR and concrete strength.

• Design & Manufacturing
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• v.11 no.3
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• pp.29-34
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• 2017

Increased demand for parts with micro-pattern structure made of metals, ceramics, and composites in various fields such as medical ultrasonic sensors, CT collimators, and ultra-small actuator parts. Micro powder injection molding (PIM) is a technology for manufacturing micro size, high volume, complex, precision, net-shape components from either metal or ceramic powder. In the present study, a standard mold with a variable insert core capable of producing various micro patterns was investigated. An injection molding test was performed on a standard mold using a line type micro-pattern core having an aspect ratio of 2, a slenderness ratio of 70, a pattern size of $200{\mu}m$, and a pattern spacing of $150{\mu}m$. During the filling process, the deformation of the mold with large aspect ratio and slenderness ratio was analyzed by the experiment and the numerical simulation according to the position of the gate. We proposed a mold structure that minimizes mold deformation by gate modification and enables uniform pattern filling behavior.

• Steel and Composite Structures
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• v.44 no.3
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• pp.295-307
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• 2022

The objective of this research is to study experimentally the behavior of stiffened steel tubes (CFSTs). Considered parameters are stiffening methods by through-bolts or shear connectors with different configurations. In addition, the effect of global (ratio between length to diameter) and local (proportion between diameter to thickness) slenderness ratios are investigated. Load application either applied on steel only or both steel and concrete is studied as well. Case of loading on steel only happens when concrete inside the column shrinks. The purpose of the research is to improve the behavior of CFSTs by load transfer between them and different stiffening methods. A parametric experimental study that incorporates thirty-three specimens is carried out to highlight the impact of those parameters. Different outputs are recorded for every specimen such as load capacities, vertical deflections, longitudinal strains, and hoop strains. Two modes of failure occur, yielding and global buckling. Shear connectors and through-bolts improve the ultimate load by up to 5% for sections loaded at steel with different studied global slenderness and local slenderness equal 63.5. Meanwhile, shear connectors or through bolts increase the ultimate load by up to 6% for global slenderness up to 15.75 for sections loaded on composite with local slenderness equals 63.50. Recommendations for future design code development are outlined.

• Steel and Composite Structures
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• v.38 no.2
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• pp.121-139
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• 2021

Ultra-high strength concrete (UHSC) encased steel columns are receiving growing interest in high-rise buildings owing to their economic and architectural advantages. However, UHSC encased steel columns are not covered by the modern fire safety design code. A total of 14 fire tests are conducted on UHSC (120 MPa) encased steel columns under constant axial loads and exposed to ISO-834 standard fire. The effect of load ratio, slenderness, stirrup spacing, cross-section size and concrete cover to core steel on the fire resistance and failure mode of the specimens are investigated. The applicability of the tabulated method in EC4 (EN 1994-1-2-2005) and regression formula in Chinese code (DBJ/T 15-81-2011) to fire resistance of UHSC encased steel columns are checked. Generally, the test results reveal that the vertical displacement-heating time curves can be divided into two phases, i.e. thermal expansion and shortening to failure. It is found that the fire resistance of column specimens increases with the increase of the cross-section size and concrete cover to core steel, but decreases with the increase of the load ratio and slenderness. The EC4 method overestimates the fire resistance up to 186% (220 min), while the Chinese code underestimates it down to 49%. The Chinese code has a better agreement than EC4 with the test results since the former considers the effect of the load ratio, slenderness, cross section size directly in its empirical formula. To estimate the fire resistance precisely can improve the economy of structural fire design of ultra-high strength concrete encased steel columns.

• Journal of Korean Society of Steel Construction
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• v.11 no.1 s.38
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• pp.69-78
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• 1999

When the lateral forces are applied to a frame, columns in the frame are usually accompanied with sidesway. If this sidesway is large, the frame is subjected to buckling and an early yielding of members which reduces the overall frame stiffness. In this study, numerical analysis of frames were conducted to evaluate the ultimate lateral strength of steel moment resisting frames permitted to sidesway under axial and lateral forces, and develope the procedure for determining the limits of column slenderness ratios. In the numerical analysis, the effects of the relative stiffness ratio between beam and column, deterioration of overall frame stiffness, slenderness ratio and loading conditions were considered. The elasto-plastic analysis method in which the $P-{\Delta}$effect is implemented, presented by the author previously, was adopted in the analysis. Incremental lateral forces were applied to the frame under constant axial loads and the generalized inverse is employed for the post-ultimate behavior.

• Journal of Korean Society of Steel Construction
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• v.17 no.2 s.75
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• pp.161-171
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• 2005

When the in-plane flexural rigidity is small in relation to the applied load, the arch ribs may buckle to the in-plane direction. Designers should therefore determine the in-plane buckling strength. To determine the buckling strength of arch ribs, designers have to consider the material nonlinear response. But in the case of arch ribs having large slenderness ratio, arch ribs may buckle in the elastic range, and when the arch ribs have low slenderness ratio, elastic buckling strength is useful in the preliminary design. In this paper, elastic buckling strength of arch ribs, which are frequently used in practical design, is studied using nonlinear finite element method. In general, the relation between flexural rigidity and elastic buckling strength is linear. As seen from the results, however, when the arch ribs have low slenderness ratio, the relation between flexural rigidity and elastic buckling strength is nonlinear.

• Steel and Composite Structures
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• v.33 no.3
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• pp.375-388
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• 2019

This paper aims to investigate the axial load behavior and stability strength of square tubed steel-reinforced concrete (TSRC) columns. Unlike concrete filled steel tubular (CFST) column, the outer steel tube of a TSRC column is mainly used to provide confinement to the core concrete. Ten specimens were tested under axial compression, and the main test variables included length-to-width ratio (L/B) of the specimens, width-to-thickness ratio (B/t) of the steel tubes, and with or without stud shear connectors on the steel sections. The failure mode, ultimate strength and load-tube stress response of each specimen were summarized and analyzed. The test results indicated that the axial load carried by square tube due to friction and bond of the interface increased with the increase of L/B ratio, while the confinement effect of tube was just the opposite. Parametric studies were performed through ABAQUS based on the test results, and the feasibility of current design codes has also been examined. Finally, a method for calculating the ultimate strength of this composite column was proposed, in which the slenderness effect on the tube confinement was considered.