• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.284-289
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• 1993

To analyze the effects of compressive strength of concrete and longitudinal steel ratio on buckling behavior of columns, 36tied reinforced concrete columns with hinged ends were tested. The 100mm square cross section was used and the amount of eccentricity was 10mm. The compressive strengths of column specimens with slenderness ratios of 15, 30 and 50 were 202, 513 and 752 kg/$\textrm{cm}^2$. The longitudinal steel ratio of columns with bending about a section diagonal and about a principal axis were 2.85%(4-D10). The ratio of ultimate load capacity to that of short column with the same eccentricity was much decreased at high slenderness ratio with increasing the compressive strength of concrete. And the lateral displacement of column at the ultimate load was decreased as the strength was increased. These are due to that at high slenderness ratio, the load capacity and behavior of column are affected by flexural rigidity. And, it was also found that for the same quantity of confining steel and level of axis load, there is little difference between the flexural strength for bending about a section diagonal and for bending about principal axis.

• Earthquakes and Structures
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• v.15 no.4
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• pp.419-429
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• 2018

The seismic vulnerability analysis of multi-span bridges can be based on the response of the piers, provided that deck, bearings and foundations remain elastic. The lateral response of an RC bridge pier can be affected by different mechanisms (i.e., flexure, shear, lap-splice or buckling of the longitudinal reinforcement bars, second order effects). In the literature, simplified formulations are available for mechanisms different from the flexure. On the other hand, the flexural response is usually calculated with a numerically-based Moment-Curvature diagram of the base section and equivalent plastic hinge length. The goal of this paper is to propose a simplified analytical solution to obtain the Moment-Curvature relationship for hollow circular RC sections. This based on calibrated polynomials, fitted against a database comprising 720 numerical Moment-Curvature analyses. The section capacity curve is defined through the position of 6 characteristic points and they are based on four input parameters: void ratio of the hollow section, axial force ratio, longitudinal reinforcement ratio, transversal reinforcement ratio. A case study RC bridge pier is assessed with the proposed solution and the results are compared to a refined numerical FEM analysis, showing good match.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.949-954
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• 2013

Generally, structural plates under axial compression should be stiffened by longitudinal stiffeners in order to enhance the buckling strength. Though U-shaped ribs would be more efficient for the stiffened plate system, there is in the absence of a proper design guides or relevant research results. Thus this study is aimed to examine the local buckling behavior of stiffened plates with U-section ribs. 3-dimensional analysis models which include 3 types of U-shaped longitudinal stiffeners were simulated by using the finite element code ABAQUS. The bifurcation analysis were conducted and then the buckling analysis results are compared with the theoretical equation values. It is found that the rotational constraint effect provided by the U-ribs should increase the local buckling strength. Some features drawn from a series of parametric study results are summarized.

• International Journal of Highway Engineering
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• v.16 no.6
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• pp.59-67
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• 2014

PURPOSES : The purpose of this study is to analyse the longitudinal steel strain and stress of continuously reinforced concrete pavement(CRCP) with longitudinal and transverse direction at early age using stress dependent strain analysis method. METHODS : To measure the longitudinal steel strain, 9-electrical resistance and self-temperature compensation gauges were installed to CRCP test section (thickness = 250mm, steel ratio = 0.7%) and continuously measured 10min. intervals during 30days. In order to properly analyze the steel stress first, temperature compensation process has been conducted. Secondly, measured steel strains were divided into stress dependent strain (elastic strain) and stress independent strain (thermal strain) and then stress dependent strain was applied to stress calculation of longitudinal steels. RESULTS : Steel strains were successfully measured during 30days. To verify the accuracy of temperature compensation process, measured coefficient of thermal expansion(COTE,$11.46{\times}10^{-6}m/m/^{\circ}C$) of longitudinal steel before paving was compared with that of unrestrained steel. Max. steel stress in the transverse direction shows about 266MPa at 23days after placement. CONCLUSIONS : Steel stresses in the longitudinal and transverse direction have been evaluated. In longitudinal direction, steel stress from the crack was rapidly reduced from 183MPa at crack to 18MPa from 600mm apart the crack. From this observation, stress effective length can be identified as within 600mm apart from the crack. In transverse direction, max. stress point was located near the center of pavement width and stress level(266MPa) is about 66% of yield stress of steel.

• Design & Manufacturing
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• v.17 no.4
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• pp.33-41
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• 2023

Excessive use of plastic bottles contributes to a significant environmental issue due to the high volume of plastic waste generated. To address this, efforts are needed to reduce the weight of plastic bottles. However, indiscriminate weight reduction may compromise the essential rigidity required for plastic bottles. Extensive research on rib shape for pressure vessels are exists, but there is a few research of rib shapes to enhance the stiffness of plastic bottles. The following results were obtained from the analyses conducted in this study. 1) Among the rib cross-sections of square, trapezoid, and triangle, the buckling critical load of PET bottles with square-shaped ribs is improved by about 14% compared to the buckling critical load of PET bottles without ribs. 2) The buckling critical load is improved by about 18% when a square-shaped rib with an aspect ratio of 0.2 is applied, compared to the buckling critical load of the bottle without the rib. 3) When longitudinal and transverse square ribs were applied to the axial direction of the PET bottle, the buckling critical load was improved by about 32% and 58% compared to the buckling critical load of the PET bottle without ribs, respectively, indicating that applying longitudinal ribs is effective in reinforcing the stiffness of PET bottles. 4) When 14 transverse ribs were applied, the maximum improvement was about 48% compared to the buckling critical load of the plastic bottle without ribs. 5) When 3 longitudinal ribs were applied on each side, the maximum improvement was about 76% compared to the buckling critical load of the bottle without ribs. Therefore, it was concluded that for effective stiffness reinforcement of a 500ml square bottle with a thickness of 0.5mm, 3 square-shaped ribs with an aspect ratio of 0.2 should be applied in the longitudinal direction relative to the axial direction of the bottle.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.816-825
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• 2002

During the manufacture of a ship, longitudinal deformation is produced by fillet welding on the BuiltUp beam used to improve the longitudinal strength of a ship. This deformation needs a correcting process separate from a manufacture process and decreases productivity and quality. This deformation is caused by welding moment, which is the value multiplied the shrinking force due to welding by the distance from the neutral axis on a cross section of Built-Up beam. This deformation can be offset by generating a moment which is the same magnitude with and is located in an opposite direction to the welding moment on web plate by induction heating. Accordingly, this study clarifies the creation mechanism of the longitudinal deformation on Built-Up beam with FEM analysis and presents the preventative method of this deformation by induction heating basing the mechanism and verifies its validity through analysis and experiments. The induction heating used here is performed by deciding its location and quantity with experiments and simple equations and by applying them to areal structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.155-158
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• 1998

This paper is calculated at electron swarm simulation by Back Prolongation of Boltzmann equation for range of E/N values from 0.1~200[Td], pressure P= 1.0[Torr], temperature T=300[ 。K], the electron swarm parameter(drift velocity, longitudinal . transverse diffusion coefficients, characteristic energy, etc) in He gas is used by electron collision cross section, particularly explicate the simulation technique, and consider electrical conduction characteristic of He gas.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.589-596
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• 1998

Experimental studies are investigated for RC column retrofitting under cyclic load. Design considerations are jacketing of steel plate of carbon fiber with epoxy bonding, use of unbonded plate, additional concrete grouting, ratio of additional longitudinal steel reinforcement and longitudinal configuration of additional ties. Investigated results are 1) jacketing and additional reinforcements are effective for strengthening, 2) use of additional grouting is less effective with respect to increased section. Future studies are needed to evaluate the requirements about additional reinforcements for member stress level, 3) bond between original and additional grout concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.941-946
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• 2001

The objectives of this study are to investigate effective stiffness of Rectangular reinforced concrete bridge columns. It is reasonable to use yielding effective stiffness of columns in seismic bridge design, especially in case that plastic hinges form at the bridge columns. In this study, the material nonlinear analysis was conducted for 3, 240 column sections of which variables were the concrete compressive stress, the steel yielding stress, the longitudinal steel location parameter, the longitudinal steel ratio, the axial load level, and the diameter of section. Based on the analytical results, an effective stiffness including two variables(longitudinal steel ratio and axial load ratio) was proposed by regression analyses, and it is compared with test results and the proposed equation for yielding effective stiffness of circular bridge columns.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.591-596
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• 2001

In case of continuous steel box-girder bridges, the magnitude of the longitudinal tensile stress on concrete in internal support is larger than the tensile strength of concrete. In this paper, the parametric study was performed to present the effective magnitude of the longitudinal prestress for reducing the longitudinal tensile stress to decrease under the tensile strength of concrete. The parametric study is conducted with changing the steel box-girder section and the span length of bridge. Three dimensional finite element analyses are conducted with ABAQUS program. The behavior of the steel box-girder bridge with prestress is investigated through experimental works on a analogous steel box-girder bridge model, and their results are compared with those of analytical studies.