• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.4A
• /
• pp.611-620
• /
• 2006

The composite two plate-girder bridges are generally defined as a non-redundant load path structure because the bridge can collapse if one of the two girders is seriously damaged by a fatigue crack. In this paper, a numerical study on the evaluation of the after-fracture redundancy of the composite two-girder bridges was accomplished. The evaluation has been performed on the simple and three-span continuous bridges with I-section cross beams which serve as transverse bracing, and with or without the bottom lateral bracing system. The load carrying capacities of the intact and damaged bridges with or without lateral bracing were evaluated from material and geometric nonlinear analysis, respectively and the redundancy was evaluated for each case. It was acknowledged from the analytical results that both simple and continuous intact two-girder bridges have sufficient redundancy even without lateral bracing, but it takes an important role to improve the redundancy of damaged bridges.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.13 no.2
• /
• pp.245-256
• /
• 2000

A moment-curvature relationship to simulate the behavior of reinforced concrete beam under cyclic loading is introduced. Unlike previous moment-curvature models and the layered section approach, the proposed model takes into consideration the bond-slip effect by using monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The advantages of the proposed model, comparing to layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures. The modification of the moment-curvature relation to reflect the fixed-end rotation and pinching effect is also introduced. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed model.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.993-999
• /
• 2008

A girder height limitation is the critical parameter for rapid construction of bridge deck and construction space limitation especially in urban area such as high population area and high density habitats. A standard post-tensioned I-shaped concrete girder usually demands relatively higher girder height in order to retain sufficient moment arm between compression force and tensile force. To elaborate this issue, a small U-shaped section with wide flanges can be used as a possible replacement of I-shaped standard girder. This prestressed concrete box girder allows more flexible girder height adjustment rather than standard I-shaped post-tensioned girder plus additional torsion resistance benefits of closed section. A 30m-long, 1.7m-high and 3.63m-wide actual small prestressed concrete box girder is designed and a laboratory test for its static behaviors by applying 6,200kN amount of load in the form of 4-point bending test was performed. The load-deflection curve and crack patterns at different loading stage are recorded. In addition, to extracting the dynamic characteristics such as natural frequency and damping ratio of this girder, several excitation tests with artificial mechanical exciter with un-symmetric mass are carried out using operational frequency sweep-up. Nonlinear finite element analysis of this 4 point bending test under monotonic static load is investigated and discussed with aids of concrete damaged plasticity formulation using ABAQUS program.

• Journal of the Korea Concrete Institute
• /
• v.24 no.5
• /
• pp.559-566
• /
• 2012

In this study, fiber elements and a spring are used to build a reinforced concrete shear wall model. The fiber elements and the spring reflect flexural and shear behaviors of the shear wall, respectively. The fiber elements are built by inputting section data and material properties. The spring parameters representing strength and stiffness degradation, pinching, and slip were determined by comparing behaviors of fiber element and VecTor2 results. 'Pinching4' model in OpenSees is used for shear spring. The parameter selecting process for shear spring is a complicated and time consuming process. To study the applicability of the fiber element, reinforced concrete buildings containing a shear wall are evaluated using nonlinear dynamic analysis with various wall aspect ratio (H/L), various beam heights, and stiffness and flexural strength of beam and wall ratios. The aspect ratio of the wall showed distinct difference in IDR (interstory drift ratio) of the models with and without spring. On the other hand, the height of beam and ratio of stiffness and flexural strength of beam and wall did not show clear relation.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.2
• /
• pp.138-145
• /
• 2017

The purpose of this study is to establish a reasonable analytical method for the estimation of overall behavior characteristic from cracking to yielding of rebar and crushing of concrete and seismic performance of reinforced concrete shear wall with high-strength reinforcing bar. A total of 8 specimens of reinforced concrete walls which have constant aspect ratio and a variety of variables such as reinforcement ratio, reinforcement yielding strength, reinforcement details, concrete design strength, section shape and whether lateral restraint hoop were selected and the analysis was performed by using a non-linear finite element analysis program (RCAHEST) applying the proposed constitutive equation by the authors. The mean and coefficient of variation for maximum load from the experiment and analysis results was predicted 1.04 and 8%. The mean and coefficient of variation for displacement corresponding maximum load from the experiment and analysis results was predicted 1.17 and 19% respectively. The analytical results were predicted relatively well the fracture mode and the overall behavior until fracture for all specimens. These results are expected to be used as basic data for application of high-strength reinforcing bar to design codes in the future.

• Composites Research
• /
• v.28 no.4
• /
• pp.212-218
• /
• 2015

A large composite spar was manufactured using an automatic fiber placement (AFP) machine. To verify its structural performance, the weakest part of the structure, which is called 'corner radius', was tested under bending and examined by finite element analysis. Since the application of AFP machine to composite structure fabrication is still in early stage in Korea, this paper presents the summary of whole process for manufacturing composite spar using AFP machine from mandrel design and analysis to verification test. The deflection and stress by mandrel weight and AFP machine force, thermal deformation and natural frequency were all examined for mandrel design. The target structure was composite C-spar and cured in an autoclave. Test results were compared with nonlinear finite element analysis results to show that the structure has the strength close to the theoretical value. It was confirmed that the corner radius of the spar manufactured by AFP process showed deviation less than 20% compared with first ply failure strength. The results indicate that the AFP technology could be used for large scale composite structure production in the near future.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.3
• /
• pp.130-137
• /
• 2017

The purpose of this study is to provide a reasonable analytical method for the reinforced concrete beams which shows failure mode of shear and flexure-shear by proposing a modified formulation to consider the effect of shear deformation on the beam-column fiber element based on the flexibility method and a new constitutive law of inelastic shear response history for the section. A total of 6 specimens of reinforced concrete beams which is designed to cause shear failure before yielding longitudinal reinforcement to investigate the influence of the main experimental variables on the shear behavior characteristics and the analysis was performed by using a non-linear finite element analysis program (RCAHEST) applying the newly modified constitutive equation by the authors. The failure mode and the overall behavior characteristics until fracture are predicted appropriately for all specimens and the results are expected to be useful enough for the 3 - D analysis to carry out reliable results of large-scale and complicated structures in the future.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.1
• /
• pp.35-42
• /
• 2020

Torsional behavior due to the plane irregularities of the piloti building can cause excessive story drift in the torsionally outermost column, which can lead to shear failure of the column. As a seismic retrofit method that can control the torsional behavior of the piloti building, the expansion of RC wall, steel frame or steel brace may be used, but such methods may hinder the openness of the piloti floor. Therefore, in this study, linear dynamic analysis and nonlinear static analysis for piloti buildings retrofitted by knee brace were performed, and seismic performance evaluation and torsion control effect of knee brace were analyzed. The results showed that the shear force of the column increased when the piloti building retrofitted by knee brace, but it was effective in controlling the torsional deformation. In case of retrofit between knee brace and column by 30°, the shear force of the column increased less than that of 60°, and the lateral displacement of column was decreased in the order of □, ◯ and Ｈ in cross-section.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
• /
• v.7 no.3
• /
• pp.371-381
• /
• 2017

This paper presents a methodology for creating abstract animation based on the human movement theories originating from the work of dance theorist Rudolf von Laban. Laban Movement Analysis is a method and language for describing, visualizing, interpreting and documenting all varieties of human movement, and Choreutics is based on universal patterns of nature and of human as part of a universal design. Laban defines the space of movements in a profoundly dualistic way. Outwardly, his objective and scientific definitions provide a concrete base for generating human movements in computer graphics in terms of geometric and motion primitives such as points, lines, planes, polygons, linear and nonlinear movements. On the other hand, he also offers a system for understanding the subtle characteristics about the way a movement is dynamically done with respect to inner intention. Laban's interpretations of human motion can be utilized potentially in plastic arts and computer arts. Our work was inspired by those physical and psychological analyses and computer algorithms have been developed for creating abstract animation. We presented our computer animation works entitled "Choreography" in the exhibitions: a special section in "2015 Craft Trend Fair" and "Make Your Movement" held in the Korean Cultural Centre in UK, 2016. In this paper, we describe our ideas and methods for creating abstract object movements based on the Laban's motion representations.

• Journal of Korean Society of Steel Construction
• /
• v.29 no.2
• /
• pp.111-122
• /
• 2017

In this paper, the applicability of a 1900mm-deep concrete-filled U-shaped composite beam to composite ordinary moment frames (C-OMFs) was investigated based on existing test results from smaller-sized specimens and supplemental numerical studies since full-scale seismic testing of such a huge sized beam is practically impossible. The key issue was the web local buckling of concrete-filled U section under negative bending. Based on 13 existing test results compiled, the relationship between web slenderness and story drift capacity was obtained. From this relationship, a 1900mm-deep mega beam, fabricated with 25mm-thick plate was expected to experience the web local buckling at 2% story drift and eventually reach a story drift over 3%, thus much exceeding the requirements of C-OMFs. The limiting width to thickness ratio according to the 2010 AISC Specification was shown to be conservative for U section webs of this study. The test-validated supplemental nonlinear finite element analysis was also conducted to further investigate the effects of the horizontal stiffeners (used to tie two webs of a U section) on web local buckling and flexural strength. First, it is shown that the nominal plastic moment under negative bending can be developed without using the horizontal stiffeners, although the presence of the stiffeners can delay the occurrence of web local buckling and restrain its propagation. Considering all these, it is concluded that the 1900mm-deep concrete-filled U-shaped composite beam investigated can be conservatively applied to C-OMFs. Finally, some useful recommendations for the arrangement and design of the horizontal stiffeners are also recommended based on the numerical results.