• Proceedings of the Safety Management and Science Conference
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• 2008.04a
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• pp.185-196
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• 2008

The objective of this study is to evaluate the mechanical behaviors and structural integrity of the weldment of high strength steel by using an acoustic emission (AE) techniques. Simple tension and AE tests were conducted against the 3 kind of welding test specimens. In order to analysis the effectiveness of weldability, joinability and structural integrity, we used K-means clustering method as a unsupervised learning pattern recognition algorithm for obtained multivariate AE main data sets, such as AE counts, energy, amplitude, hits, risetime, duration, counts to peak and rms signals. Through the experimental results, the effectiveness of the proposed method is discussed.

• Journal of the Korea Safety Management & Science
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• v.10 no.4
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• pp.127-134
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• 2008

The objective of this study is to evaluate the mechanical behaviors and structural integrity of the weldment of high strength steel by using an acoustic emission (AE) techniques. Monotonic simple tension and AE tests were conducted against the 3 kinds of welded specimen. In order to analysis the effectiveness of weldability, joinability and structural integrity, we used K-means clustering method as a unsupervised learning pattern recognition algorithm for obtained multi-variate AE main data sets, such as AE counts, energy, amplitude, hits, risetime, duration, counts to peak and rms signals. Through the experimental results, the effectiveness of the proposed method is discussed.

• Structural Engineering and Mechanics
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• v.32 no.2
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• pp.269-282
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• 2009

Responding to the threat of terrorist attacks around the world, numerous studies have been conducted to search for new methods of vulnerability assessment and protective technologies for critical infrastructure under extreme bomb blasts or high velocity impacts. In this paper, a two-dimensional behavioral rate dependent lattice model (RDLM) capable of analyzing reinforced concrete members subjected to blast and impact loading is presented. The model inherently takes into account several major influencing factors: the progressive cracking of concrete in tension, the inelastic response in compression, the yielding of reinforcing steel, and strain rate sensitivity of both concrete and steel. A computer code using the explicit algorithm was developed based on the proposed lattice model. The explicit code along with the proposed numerical model was validated using experimental test results from the Woomera blast trial.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.61-64
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• 2004

This study presents results from an experimental work for two normal prestressed concrete beams and three dual prestressed concrete beams. The dual prestressed concrete beams made with normal concrete in compression zone and high performance steel fiber reinforced concrete in partial depth of tension zone. Through cyclic loading test under low frequency, structural behavior and resistance to dynamic loading for dual prestressed concrete beams are investigated. Considerable increase of crack and yield load capacity of Dual prestressed concrete beam is shown compared with normal prestressed concrete beam. In addition, re-loading and un-loading rigidity of dual prestressed concrete beam under cyclic loading are increased comparing with normal prestressed concrete beam.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.541-549
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• 2003

Split-tee connection with High Strength Bolts is normally used in low and middle rise buildings in Europe because the structural efficiency and installation work of connections are excellent. However, the domestic situation is different from that in Europe. The analysis and the design for the T-split connection are complicated, because the structural behavior often T-split connection with High Strength Bolt is governed by so many parameters, i.e., prying action, bolt's tension, shear failure and plastic failure of flange plates. Many researches regarding the structural behavior of the split-tee connection have been undertaken in other parts of the world, such as the, Americas, Japan and Europe, but in the domestic context, this is a pioneering study. Therefore, the purpose of this paper is to supply basic data for the design of T-split connection, and to verify the structural characteristics that define reactions to prying action, based on an experimental study.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.304-307
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• 2004

Direct tensile tests were carried out for the tensile members of MMA-modified polymer concrete with different steel kinds and steel diameters and steel ratios to figure out the effect of tensile strength of polymer concrete. In the experiments, MMA-modified polymer concrete with $1000\;kgf/cm^2$ of compressive strength, steel with $5200\;kgf/cm^2$ of tensile strength, and the tensile members with 100 cm of constant length were used. Experimental results showed that, regardless of steel kinds, diameters and steel content, the strain energy exerted by concrete till the initial crack was $14-15\%$ of the total energy till the point of yield: The energy was much larger than the one of high-strength cement concrete. The behaviors of tensile members of MMA-modified polymer concrete were in relatively good agreement with the model suggested by Gupta-Maestrini (1990), which was idealized by the effective tensile stress-strain relationship of concrete and the load-strain relationship of members, while those showed a big difference from CEB-FIP model and ACI-224 equation suggested for the load-displacement relationship that was defined as the cross sectional stiffness of effective axis. Modified ACI-224 model code about the load-displacement relationship for the tensile members of MMA-modified polymer concrete and theoretical equation for the polymer concrete tensile stiffness of polymer concrete suggested through the results of this study are expected to be used in an accurate structural analysis and resign for the polymer concrete structural members.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.191-199
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• 1999

This paper is the first step on the study of the industrialization of the mid-story steel building structures. The purpose of this study is to investigate the structural behavior of concrete-filled square steel tubular column to H-beam connections using angles and high tension bolts. The tests are carried out with five types of specimens under static loading and the main parameter is the thickness of angles. Yield-line theory which obtains connection strength by way of the lowest value based on upper-limit theory is applied to predict strength formulas.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.421-430
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• 1997

In this study, the static and the fatigue tests were performed with high tension bolted joints, of which the surfaces were spread with inorganic zinc-primer after shot-blast, and milling surface, and steel-natural surface, difference of friction surface condition were examined by comparing the esults of tests. From the result of synthetical investigation of this study. it is proper that using the torque management method in order to introduce design axial force to blots, and the provision of specifications that initial axial forces must be 110% of design axial forces is proper. Decreasing ratio of axial forces to initial force is proportional to common lorgarithms of time progress, it converge constant value after 20 hours, and decreasing ratio is little related to the roughness of friction surface. Sliding coefficient of milling, spreading inorganic zinc-primer, just producting is great in order and sliding forces are dependent on the applied axial forces, but if the applied axial forces are great, sliding coefficient become small by a loss of roughness. So it is confirmed that relation between the applied axial forces and the sliding forces are not proportional linearly. From the result of estimation on fatigue strength, all specimens satisfy the specifications with B-grade and milling surface is lower than the others about 14% in fatigue strength because in milling surface lose the function of friction-types joints at lower number of cycles. From the result of eximination for the distribution area of compressive force, friction area near to inside bolt is wider in the direction of stress than near to outside. It is guessed that this situation occurs because outside bolts firstly change from the friction connection to the bearing connection.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.531-539
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• 2003

Unlike field-welded moment frames damaged during the Northridge earthquake, a column-tree moment frame has a tool to control and reduce its seismic behavior. The tool is the girder splice. Girder splices could be designed to be sufficiently ductile and to have a prescribed bending moment capacity. In such a design, during earthquakes, the girder splices would act as ductile "fuses" and limit the magnitude of forces including the bending moment that could be developed in the frame. In Korea, most moment frames arc composed of a column-tree moment frame. Therefore, the elasto-plastic behavior of steel beams with high strength bolted friction splice should be clarified. Furthermore, structural capacities, including energy absorption capacity, must be quantitatively found. This paper discusses an experimental study to clarify elasto-plastic behavior of steel beams with high strength bolted friction splices. A total of 5 specimens were tested. A specimen was fabricated to have a beam splice designed by a full strength method. Other specimens were fabricated to have beam splices with 75%, 50% and 0% capacities compared with the specimen.

• Progress in Superconductivity and Cryogenics
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• v.19 no.4
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• pp.26-30
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• 2017

The promising characteristics of 2G high-temperature superconductor (HTS) coated conductor (CC) tapes have made it possible to apply to various electrical device applications. In this study, the mechanical and electromechanical properties of Sn-Cu double layer stabilized GdBCO CC tapes have been characterized. The stress and strain tolerances of $I_c$ in GdBCO CC tapes adopting stainless steel substrate were evaluated using $I_c$-strain measurement at 77 K under both uniaxial tension and monotonic bending conditions. The results were compared to the conventional single Cu layer stabilized CC tape. As a result, the Sn-Cu double layer stabilized GdBCO CC tapes showed somehow lower or comparable electromechanical properties as compared to the Cu stabilized CC tape ones.