• Journal of the Korean Society for Railway
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• v.3 no.3
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• pp.117-124
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• 2000

The rubber wheel-type AGT has two major kinds of bogie; one is the bogie type and the other steering one. Both are important vehicular structure to support the whole running vehicle and passenger loads. This paper deals with the static analysis for the two types of bogie frame subjected to combined external forces, as well as independent ones specified in UIC 515-4. Furthermore, the dynamic analysis is performed under vibrational loading conditions so as to compare dynamic characteristics, Numerical results by using commercial packages, I-DEAS and NASTRAN show that maximum stresses do not exceed the yield strength level of material used for both bogies. From an overall viewpoint of strength, the bogie type turns out to be superior to the steering type except for the case of a lateral loading. It is also observed that the steering type shows a characteristics of low frequency behavior during a course of searching for structurally weak areas to be stiffened. The vibrational fatigue analysis for each bogie frame depends on the loading time history conditions which is applied. Time History Central Database List in the NASTRAN package. Subsequent1y, the fatigue life of bogie type is longer than the steering type.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.1
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• pp.1-9
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• 1999

This study was performed to investigate the deinkability of Korean old newspaper(KONP) and the properties of newsprint made from deinked pulp with some addition of virgin pulp. When the samples of composed of 50% Australian old magazine(AuOMG) and 50% KONP were compared with the samples 50% AuOMG and 50% AuONP, the yield, opacity, strength properties of the former were high, but its brightness was low. When the mixing ratio of AuOMG : AuONP : KONP was 30:20:50, the brightness and strength properties were obtained the similar or better than those obtained samples having other mixing ratio. The brightness and opacity of samples made from deinked pulp with the some addition of TMP and BKP can meet the minium qualifications of brightness and opacity specified by Japanese Industrial Standard. The samples, which DIP, TMP, and KP were mixed with the ratio of the 85:10:5 and 90:5:5, maintained higher brightness and strength comparing to the samples containing higher amount of virgin pulp. Since the newsprint samples made from KONP was not inferior to those from imported old newspaper, the more use of KONP in producing newsprint is recommended.

• Journal of Korean Society of Steel Construction
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• v.29 no.4
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• pp.291-301
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• 2017

Most of current representative design standards worldwide forbid or impose restrictions on the use of high-strength steels for hollow tubular structures. The mechanical background of these limitations appears unclear and unduly conservative, and their validity needs to be re-evaluated. In this study, a total of 9 CHS(Circular Hollow Section) X-joints were tested under axial compression and analyzed to examine if the high-strength steel restrictions specified by current design standards could be relaxed. All the high-strength steel CHS X-joints tested showed satisfactory performance compared to ordinary steel joints in terms of serviceability, ultimate strength, and ductility, although the yield strength of steel was even as high as 800MPa.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.99-109
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• 2012

This study aimed to develop a Structural Health Monitoring System for steel beams in the manner of suggesting and verifying a theoretical formula for displacement estimation using strain gauges, and estimating the loading points and magnitude. According to the results of this study, it was found that when a load of 160kN (56% of the yield load) was applied, the error rate of the deflection obtained with a strain gauge at the point of maximum deflection compared to the deflection measured with a displacement meter was within 2%, and that the estimates of the magnitude and points of load application also showed the error rate of not more than 1%. This suggests that the displacement and load of steel beams can be measured with strain gauges and further, it will enable more cost-effective sensor designing without displacement meter or load cell. The Structural Health Monitoring System program implemented in Lab VIEW gave graded warnings whenever the measured data exceeds the specified range (strength limit state, serviceability limit state, yield strain), and both the serviceability limit state and strength limit state could be simultaneously monitored with strain gauge alone.

• Journal of Korean Society of Steel Construction
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• v.25 no.2
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• pp.115-130
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• 2013

In this study, lateral-torsional buckling (LTB) strength of high-strength H-beams built up from 800MPa tensile-strength steel was experimentally and analytically evaluated according to current lateral stability provisions (KBC 2009, AISC-LRFD 2010). The motivation was to evaluate whether or not current LTB provisions, which were originally developed for ordinary steel with different stress-strain characteristics, are still applicable to high-strength steel. Two sets of compact-section specimens with relatively low (Set A) or high (Set B) warping stiffness were prepared and tested under uniform moment loading. Laterally unbraced lengths of the test specimens were controlled such that inelastic LTB could be induced. All specimens exhibited LTB strength exceeding the minimum limit required by current provisions by a sufficient margin. Moreover, some specimen in Set A reached a rotation capacity required for plastic design, although its laterally unbraced length belonged to the inelastic LTB range. All the test results indicated that extrapolation of current provisions to high-strength steel is conservative. In order to further analyze the test results, the relationship between inelastic moment and laterally unbraced length was also derived in explicit form for both ordinary- and high-strength steel based on the effective tangent modulus of inelastic section. The analytical relationship derived again showed that extrapolation of current laterally unbraced length limit leads to a conservative design in the case of high-strength steel and that the laterally unbraced length to control the inelastic LTB behavior of high-strength steel beam should be specified by including its unique post-yield strain-hardening characteristics.

• Earthquakes and Structures
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• v.13 no.4
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• pp.409-419
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• 2017

In order to analyze the vibration control effect of viscous damper in the concrete archaized buildings with lintel-column joints under seismic action, 3 specimens were tested under dynamic excitation. Two specimens with viscous damper were defined as the controlled component and one specimen without viscous damper was specified as the non-controlled component. The loading process and failure patterns were obtained from the test results. The failure characteristics, skeleton curves and mechanical behavior such as the load-displacement hysteretic loops, load carrying capacity, degradation of strength and rigidity, ductility and energy dissipation of the joints were analyzed. The results indicate that the load-bearing capacity of the controlled component is significantly higher than that of the non-controlled component. The former component has an average increase of 27.4% in yield load and 22.4% in ultimate load, respectively. Meanwhile, the performance of displacement ductility and the ability of energy dissipation for the controlled component are superior to those of the non-controlled component as well. Compared with non-controlled component, equivalent viscous damping coefficients are improved by 27.3%-30.8%, the average increase is 29.0% at ultimate load for controlled component. All these results reflect that the seismic performance of the controlled component is significantly better than that of the non-controlled component. These researches are helpful for practical application of viscous damper in the concrete archaizing buildings with lintel-column joints.

• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.1-12
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• 2017

This paper proposes nominal flexural strength considering strain-hardening effect of HSB600 high performance steel for compact composite I-girders in positive bending. Unlike conventional steels, HSB600 undergoes strain-hardening just after yielding without going through yield plateau. However, because the nominal flexural strength specified in domestic and foreign bridge design specifications has been developed for the conventional steel composite girders, the nominal flexural strength does not appropriately consider the strain-hardening of HSB600. Therefore, plastic moment considering a strain-hardening is proposed so as to consider effect of the strain-hardening of HSB600 on flexural strength and then moment-curvature analysis is performed to a wide range of cross-sections. From results of the analysis, a parameter representing the effect of the strain-hardening on the flexural strength of HSB600 composite girders is proposed. Furthermore, by using this parameter, the nominal flexural strength considering the strain-hardening effect for HSB600 composite I-girders in positive bending is proposed and then evaluated by comparing with the current AASHTO LRFD bridge design specifications.

• Structural Engineering and Mechanics
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• v.5 no.5
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• pp.507-521
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• 1997

The ultimate behavior of a reinforced concrete hyperbolic paraboloid saddle shell under uniformly distributed vertical load is investigated using an inelastic, large displacement finite-element program originally developed at North Carolina State University. Unlike with the author's previous study which shows that the saddle shell possesses a tremendous capacity to redistribute the stresses, introducing tension stiffening in the model the cracks developed are no longer through cracks and formed as primarily bending cracks. Even though with small tension stiffening effect, the behavior of the shell is changed markedly from the one without tension stiffening effect. The load-deflection curves are straight and the slope of the curves is quite steep and remains unchanged with varying the tension stiffening parameters. The failure of the shell took place quite suddenly in a cantilever mode initiated by a formation of yield lines in a direction parallel to the support-to-support diagonal. The higher the tension stiffening parameters the higher is the ultimate load. The present study shows that the ultimate behavior of the shell primarily depends on the concrete tensile characteristics, such as tensile strength (before cracking) and the effective tension stiffening (after cracking). As the concrete characteristics would vary over the life of the shell, a degree of uncertainty is involved in deciding a specified ultimate strength of the saddle shell studied. By the present study, however, the overload factors based on ACI 318-95 are larger than unity for all the cases studied except that the tension stiffening parameter is weak by 3 with and without the large displacement effect, which shows that the Lin-Scordelis saddle shell studied here is at least safe.

• Journal of the Korea Concrete Institute
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• v.21 no.2
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• pp.169-178
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• 2009

An equation for calculating confining reinforcement amount of RC bridge columns, specified in the current bridge design codes, has been made to provide additional load-carrying strength for concentrically loaded columns. The additional load-carrying strength will be equal to or slightly greater than the resistant strength of a column against axial load, which is lost because the cover concrete spalls off. The equation considers concrete compressive strength, yield strength of transverse reinforcement, and the section area ratio as major variables. Among those variables, the section area ratio between the gross section and the core section, varying by cover thickness, is a variable which considers the strength in the compression-controlled region. Therefore, the cross section ratio does not have a large effect in the aspect of ductile behavior of the tension-controlled region, which is governed by bending moment rather than axial force. However, the equation of the design codes for calculating confining reinforcement amount does not directly consider ductile behavior, which is an important factor for the seismic behavior of bridge columns. Consequently, if the size of section is relatively small or if the section area ratio becomes excessively large due to the cover thickness increased for durability, too large an amount of confining reinforcement will be required possibly deteriorating the constructability and economy. Against this backdrop, in this study, comparison and analysis were performed to understand how the cover thickness influences the equation for calculating the amount of confining reinforcement. An equation for calculating the amount of confining reinforcement was also modified for reasonable seismic design and the safety. In addition, appropriateness of the modified equation was examined based on the results of various test results performed at home and abroad.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.39-48
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• 2011

The present investigation evaluates the flexural behavior of pre-tensioned lightweight concrete beams under two-point symmetrical concentrated loads according to the variation of the partial prestressing ratio and the effective prestress of prestressing strands. The designed compressive strength of the lightweight concrete with a dry density of 1,770 $kg/m^3$ was 35 MPa. The deformed bar with a yield strength of 383 MPa and three-wire mono-strands with tensile strength of 2,040 MPa were used for longitudinal tensile reinforcement and prestressing steel reinforcement, respectively. According to the test results, the flexural capacity of pre-tensioned lightweight concrete beams increased with the increase of the partial prestressing ratio and was marginally influenced by the effective prestress of strands. With the same reinforcing index, the normalized flexural capacity of pre-tensioned lightweight concrete beams was similar to that of pre-tensioned normal-weight concrete beams tested by Harajli and Naaman and Bennett. On the other hand, the displacement ductility ratio of pre-tensioned lightweight concrete beams increased with the decrease of the partial prestressing ratio and with the increase of the effective prestress of strands. The load-displacement relationship of pre-tensioned lightweight concrete beam specimens can be suitably predicted by the developed non-linear two-dimensional analysis procedure. In addition, the flexural cracking moment and flexural capacity of pre-tensioned lightweight concrete beams can be conservatively evaluated using the elasticity theorem and the approach specified in ACI 318-08, respectively.