• Steel and Composite Structures
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• v.19 no.4
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• pp.861-876
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• 2015

Composite sections design consists on checking that the point defined by axial load and bending moment keeps included within the surface enclosed by the section interaction curve. Eurocode 4 suggests a method for tracing this diagram based on the plastic stress distribution method. However curves obtained according to this criterion overvalue concrete encased sections bearing capacity, especially when axial force comes with high bending moment values, so a correction factor is required. This article proposes a method for tracing this diagram based on the strain compatibility method. When stresses on the section are integrated by considering the Navier hypothesis, the use of the materials nonlinear constitutive equations provides curves much more adjusted to reality. This process requires the use of rather complex software which might reveal as too complex for practitioners. Preserving the same criteria of an elastic-plastic stress distribution, this article presents alternative expressions to obtain the failure internal forces in five significant points of the interaction diagram having considered five different positions of the neutral axis. These expressions are simply enough for their practical application. Concordance of curves traced strictly relying on these five points with those obtained by computer assisted stress integration considering the strain compatibility method and even with Eurocode 4 weighted curves will be presented for three different cross-sections and two different concrete strengths, revealing very good results.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.8-16
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• 2015

Prestressed concrete (PSC) is a method in which prestressed tendon is placed inside and/or outside the reinforced concrete member and the compressive force applied to the concrete in advance to enhance the engineering properties of concrete member which is weak under tension. In this paper we suggested the precast PSC girder assembled with segments of portable size and weight at the factory. The segments of precast PSC girder will be delivered and assembled as a unit of PSC girder at the site. Consequently, we suggested new-type of precast segmented PSC girder with different shapes of segment cross-section (i.e., I-shape, Box-shape). To mitigate the problems associated with the field splice between the segments of precast PSC girder anchor system is attached near the neutral axis of the girder and relatively uniform compression throughout the girder cross-section is applied. Prior to the experimental investigation, analytical investigation on the structural behavior of precast PSC girder was performed and the serviceability (deflection) and safety (strength) of the girder were confirmed. In addition, 4-point bending test on the girder was conducted to investigate the structural performance under bending. From the experimental investigation, it was found that the precast PSC girder spliced with 3 and 5 segments has sufficient in serviceability and safety conditions and it was also observed that the point where the segments spliced has no defects and the girder behaves as a unit.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.57-60
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• 2008

Compared with a steel-reinforced section with equal areas of longitudinal reinforcement, a cross section using FRP flexural reinforcement after cracking has a smaller depth to the neutral axis because of the lower axial stiffness. The compression region of the cross section is reduced, and the crack widths are wider. As a result, the shear resistance provided by both aggregate interlock and compressed concrete is smaller. Research on the shear capacity of flexural members without shear reinforcement has indicated that the concrete shear strength is influenced by the stiffness of the flexural reinforcement. In this research, experimental observations were made for the shear strength of FRP reinforced concrete beam and validity of existing predicting equations were examined. Test results showed that shear strength decreased as shear-span increased.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.433-439
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• 2007

The main objective of the paper is to investigate the static behavior of a prestressed concrete (PSC) girder that has been spliced with precast box segments. A 20 m long full-scale spliced PSC girder is fabricated and tested to compare its static performance against a monolithic girder. The monolithic girder has the same geometric and material properties with respect to the spliced girder. This includes infernal strain, deflections, neutral axis position, and crack patterns for both girders. The test also consists of monitoring relative displacements occurring across the joints. Both the horizontal displacement (gap) and vertical displacement (sliding) are measured throughout the loading procedure. All results have been compared to those obtained from the monolithic girder. It has been demonstrated that the spliced girder offers close behavior with respect to the monolithic girder up to the crack load. Both girders exhibits ductile flexural failure rather than abrupt shear failure at joints.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.3
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• pp.83-97
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• 1995

The aim of this study is to derive a simple formula for predicting ultimate strength of hull girders under vertical bending moment. The existing formulas have been reviewed and classified into analytical approach, empirical approach and linear approximate approach. It is known that the ship hull will reach the ultimate limit state if both collapse of the compression flange and yielding of the tension flange occur. Side shells in the vicinity of the compression and tension flanges will often fail also, but the material around the final neutral axis will remain in the elastic state. Based on this observation, a credible distribution of longitudinal stresses around the hull section at the overall collapse state is assumed, and an explicit analytical formula is derived. The accuracy of the formula has been verified by a comparison of the experimental and the numerical results.

• Korean Journal of Applied Biomechanics
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• v.27 no.2
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• pp.91-97
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• 2017

Objective: To investigate rotation movement of segment for performing each position and its effect on knee/hip angulation, COM inclination, and edging angle changes. Method: Twelve Alpine skiers (age: $25.8{\pm}4.8years$, height: $173.8{\pm}5.9cm$, weight: $71.4{\pm}7.4kg$, length of career: $9.9{\pm}4.6years$) participated in this study. Each skier was asked to perform counter-rotation, neutral, and rotation positions. Results: Shank and thigh were less rotated in the counter-rotation position than in other positions, whereas the trunk and pelvis were more counter-rotated (p<.05). Hip angulation, COM inclination, and edging angle were significantly greater in the counter-rotation position than in other positions (p<.05). Conclusion: Our finding proved that the counter-rotation position increases hip angulation, COM inclination, and edging angle. Consequently, we suggest that skiers should perform counter-rotation of the trunk and pelvis relative to the ski direction in the vertical axis for the counter-rotation position. Further analysis will continue to investigate the effects of the counter-rotation position in real ski slope with kinetic analysis.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.377-388
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• 2010

The flexural behavior of composite HSB600 and HSB800 I-girders under a positive moment was investigated using the material non-linear moment-curvature analysis method. Three representative composite sections with different ductility properties were selected as the baseline sections in this study. Using these baseline sections, the moment-curvature program was verified by comparing the flexural strength and the moment-curvature curve obtained from the program with those obtained using the non-linear FE analysis of ABAQUS. In the FE analysis, the composite girders were modeled three-dimensionally with flanges, the web, and the concrete slab as thin shell elements, and initial imperfections and residual stresses were imposed on the FE model. In the moment-curvature and FE analyses, the 28-day compressive strength of the concrete slab was assumed to be 30-50 MPa, and the HSB600 and HSB800 steels were modeled as elasto-plastic strain-hardening materials, with the concrete as the CEB-FIP model. The effects of the ductility ratio of the composite girder, the type of steel, the compressive strength of the concrete deck, and the location of the plastic neutral axis on the flexural characteristics were analyzed.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.221-230
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• 1999

A study was conducted to investigate the flexural behavior of reinforced high-strength concrete beams using Belite cement. In this study, fourteen reinforced Belite and control beams were tested. The major experimental variables are compressive strength(350kgf/$cm^2$ and 600kgf/$cm^2$)of concrete and reinforcement ratios(0.0086~0.0345). They were tested by three point loading method. Comparing with flexural behavior of normal reinforced concrete beams, the investigation were to : (1) determine experimentally the load-displacement relationships and the strain distribution on the section of test beams : (2) determine experimentally the moment-curvature and the load-neutral axis relationship of Belite ; (3) investigate the flexural ductility of Belite ; (4) estimate the ratio of the capacities of nominal moment strength as a function of ACI to as a experiment. From the test results, the flexural behavior of reinforced high-strength concrete beams using Belite cement are similar to flexural behavior of normal reinforced concrete beams.

• Steel and Composite Structures
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• v.7 no.2
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• pp.87-103
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• 2007

This paper presents some of the results from an experimental research project on the behavior of extended end-plate connections subjected to moment conducted at the Structural Laboratory of Jordan University of Science and Technology. Since the connection behavior affects the structural frame response, it must be included in the global analysis and design. In this study, the behavior of six full-scale stiffened and unstiffened cantilever connections of HEA- and IPE-sections has been investigated. Eight high strength bolts were used to connect the extended end-plate to the column flange in each case. Strain gauges were installed inside each of the top six bolts in order to obtain experimentally the actual tension force induced within each bolt. Then the connection behavior is characterized by the tension force in the bolt, extended end-plate behavior, moment-rotation relation, and beam and column strains. Some or all of these characteristics are used by many Standards; therefore, it is essential to predict the global behavior of column-beam connections by their geometrical and mechanical properties. The experimental test results are compared with two theoretical (equal distribution and linear distribution) approaches in order to assess the capabilities and accuracy of the theoretical models. A simple model of the joint is established and the essential parameters to predict its strength and deformational behavior are determined. The equal distribution method reasonably determined the tension forces in the upper two bolts while the linear distribution method underestimated them. The deformation behavior of the tested connections was characterized by separation of the column-flange from the extended end-plate almost down to the level of the upper two bolts of the lower group and below this level the two parts remained in full contact. The neutral axis of the deformed joint is reasonably assumed to pass very close to the line joining the upper two bolts of the lower group. Smooth monotonic moment-rotation relations for the all tested frames were observed.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.67-75
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• 2008

This research is to develop the steel-concrete composite lining board using section shape steel. This lining board adopts section shape steel, rectangular pipe and H-beam, instead of roll-formed steel member commonly used in other composite lining board. Consequently, it reduces fabrication effort. Efficient section which can reduce the weight of steel of the lining board is made by placing the neutral axis of the section near the lower surface of concrete. Behavior of composite section is improved by adding bolts as shear connector. Static and fatigue tests were conducted to verify the performance of the composite lining board developed. The test results indicate that serviceability as well as safety of the lining board developed is secured with good margin and reduction of steel weight can be made about 27% compared with other composite lining boards.