• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.243-253
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• 2011

This paper describes an analytical study on seismic performance of domestic reinforced concrete (RC) school building not designed by seismic provision. The seismic index and the seismic performance of the building were evaluated through Japanese standard and Midas Gen, respectively. Seismic index (Is) of the RC school buildings in the X-direction is below 0.4. Based on the seismic index, for seismic-strengthening the building, infill shear wall or steel brace with a capacity of 1,300 kN was used. According to nonlinear static analysis results, the contribution of the seismic-strengthening to the shear resistance of the school building was measured to be greater than 30%. However, as expected, shear strength of school building strengthened with infill wall dropt rapidly after peak load and much narrower ductile behavior range was observed compared to steel brace strengthened building. Also, the building strengthened with steel brace showed 30% larger spectral displacement than that strengthened with infill shear wall. In nonlinear dynamic analysis, for the time history analysis, the maximum displacement showed tendency to decrease as amount of reinforcement increased, regardless of strengthening method. It was recommended that variable soil properties and earthquake record should be considered for improving seismic performance of buildings in seismic zone.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.56-66
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• 2015

This study aims at developing a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were performed on one unreinforced beam-column specimen and two reinforced specimens with U-type precast wall panels. Seismic resistant test of anchored and welded steel plate connections manifested an average of 2.8 times increase in the maximum loading (average 591.8 kN) in comparison to unreinforced beam-column specimen. The maximum drift ratios were also shown between 1.4% and 2.7%. An analytical study was performed while assuming the RC column on the right side and the vertical element of the reinforced PC panel to behave in completely composite manner and the RC column on the left side and PC panel to behave in completely non-composite manner when loading was exerted from upper right end of RC frame of specimen to its left side. It was found with the assumptions that the overall flexural behavior in principle agreed with the experimental result.

• Journal of the Society of Disaster Information
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• v.16 no.4
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• pp.796-805
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• 2020

Purpose: A static loading test was performed to evaluate the ultimate flexural strength of a girder in which 80MPa high-strength concrete was synthesized on the compressive flange of the I-shape steel girder. Method: This test is designed and fabricated two types of specimens with different shear-connection specifications, and evaluated their ultimate flexural behavior until reaching the extreme event limit states. In addition, the ultimate strength was evaluated by comparing the test results and the results of the strain compatibility method. Result: By confirming the displacement within 0.02mm as a result of the relative slip measurement, it was verified that the two specimens secured perfect bonding. Therefore, the difference in the shear specification does not have a great effect on the stiffness, and if the specimens are completely synthesized, there is no difference in the behavior until it reaches the extreme-event limit states. Conclusion: The girder to be tested has a working load within the elastic range and meets the usability requirements for allowable deflection. Therefore, even if a part of the casing is subjected to the tensile force at the level of cracking, the deck will first reach the compression failure due to the role of the reinforcing bar.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.861-872
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• 2006

The element free Galerkin method is extended by the local partition of unity method to model the cohesive cracks in two dimensional continuum. The shape function of a particle whose domain of influence is completely cut by a crack is enriched by the step enrichment function. If the domain of influence contains a crack tip inside, it is enriched by a branch enrichment function which does not have the LEFM stress singularity. The discrete equations are obtained directly from the standard Galerkin method since the enrichment is only for the displacement field, which satisfies the local partition of unity. Because only particles whose domains of influence are influenced by a crack are enriched, the system matrix is still sparse so that the increase of the computational cost is minimized. The condition for crack growth in dynamic problems is obtained from the material instability; when the acoustic tensor loses the positive definiteness, a cohesive crack is inserted to the point so as to change the continuum to a discontiuum. The crack speed is naturally obtained from the criterion. It is found that this method is more accurate and converges faster than the classical meshless methods which are based on the visibility concept. In this paper, several well-known static and dynamic problems were solved to verify the method.

• Tunnel and Underground Space
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• v.33 no.6
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• pp.574-593
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• 2023

In this study, the effectiveness and applicability of a newly designed Compact CNS shear box for conducting direct shear tests on jointed rock specimens were investigated. CNS joint shear tests were conducted on jointed rocks with Artificially generated roughness while varying the fracture surface roughness coefficient and initial normal stress conditions. In addition, displacement data were validated by Digital image correlation analysis, fracture patterns were observed, and comparative analysis was conducted with previously studied shear behavior prediction models. Furthermore, the accuracy of the displacement data was confirmed through DIC analysis, the fracture patterns were observed, and the shear properties obtained from the tests were compared with existing models that predict shear behavior. The findings exhibited a strong correlation with specific established empirical models for predicting shear behavior. Furthermore, the potential linkage between the characteristics of shear behavior and fracture patterns was deliberated. In conclusion, the CNS shear box was shown to be applicable and effective in providing data on the shear characteristics of the joint.

• Journal of the Korea Concrete Institute
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• v.20 no.1
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• pp.51-58
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• 2008

Analytical probabilistic vulnerability analysis requires extensive computing effort as a result of the randomness in both input motion and response characteristics. In this study, a new methodology whereby a set of vulnerability curves are derived based on the fundamental response quantities of stiffness, strength and ductility is presented. A response database of coefficients describing lognormal vulnerability relationships is constructed by employing aclosed-form solution for a generalized single-degree-of-freedom system. Once the three fundamental quantities of a wide range of structural systems are defined, the vulnerability curves for various limit states can be derived without recourse to further simulation. Examples of application are given and demonstrate the extreme efficiency of the proposed approach in deriving vulnerability relationships.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.2
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• pp.31-37
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• 1997

Structural details of the three-bay-straw-roof house which was the most common form of residence as a commoner's house during ancient period are suggested. Wooden frames are used in the house. The typical form of joint used is Sagaemachum. The static lateral loading capacity of the frames is evaluated through the test on full scale models. The effects of joint type at the column head and wooden lattice on the lateral loading capacity and the failure modes of frames are analyzed. The ultimate lateral loading capacity and displacement of the ordinary frame at failure are 1.090 N and 400 mm(1/6rad), respectively. These values for the frame with high column are 4,160 N and 250 mm(1/9.6rad), respectively. The behavior of joint at column head controls the overall lateral loading capacity of the frame and shows very large nonlinearity. The general failure modes of joint for an ordinary frame and a frame with high column are shear and bending failure at the branches of Sagaemachum, respectively.

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.627-634
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• 2004

The purpose of this study is to investigate seismic performance of a bearing wall system for apartment buildings. An 1/3 scale three-story specimen was constructed and tested under cyclic lateral loads. The specimen was consisted of pierced walls and coupling elements as well as floor slabs. The bearing wall system is considered to have a adequate deformation capacity up to $2.0\%$ of roof drift ratio, and the experimental results showed the ductile load-deformation characteristics even though some walls were failed in shear Nonlinear analysis was peformed to compare the load-deformation curve obtained from the experimental program. The result of nonlinear analysis could be useful to predict the actual behavior characteristics of the bearing wall system subjected to lateral loads.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.747-757
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• 2015

The main purpose of this study is to investigate the static behavior of a horizontally curved prestressed concrete (PSC) girder. A 30m long full-scale curved PSC girder with 80.0m radius is fabricated by a portable curved form system. Deflections and concrete strains at the middle of span were measured. The obtained experimental results have been compared to those from F.E.A. analysis. When a initial crack developed, the applied load was 1.3 times the service design load and the vertical deflection at the middle of span satisfied the requirement for a live load state according to the Korea Bridge Design Specifications (2010). Also, the ductility of the full scale specimen satisfied the limit in the Specifications (2010). To verify the experimental results, a numerical F.E. analysis was carried and confirmed that the data were similar with results from the test above. The horizontally curved PSC girder fabricated on site was found to have enough strength for safety under and after construction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1741-1751
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• 2013

The main purpose of this study is to investigate the static behavior of a prestressed concrete (PSC) girder using pre-tension method. A 30m long full-scale pretension PSC girder is fabricated by the portable fabrication system and tested. All results have been compared to those obtained from F.E.A results. Deflections at the middle of girders have been measured for evaluation. Also, strains of concrete at the middle of span have been measured. From the results of experimental, the load when initial crack was developed was obtained to be 1.75 time the unfactered design load in the full-scale girder specimen. Also, the data of specimen are satisfied the desgin requirements of ductility on the Korea Bridge Design Specification(2010). In service state, the vertical deflection at center of test specimen when a initial crack was developed is satisfied the vertical deflection requirement under live load of the Korea Bridge Design Specification(2010). To verify the experimental results, we numerical analyze the test and confirmed that the data were similar with results from the test above. The pretension girder fabricated in site were found to have enough strength for safety under and after construction.