• Journal of the Korea Concrete Institute
• /
• v.12 no.1
• /
• pp.53-60
• /
• 2000

The objective of this study is to investigate the flexural behavior of reinforced concrete columns confined by lateral ties. This test was carried on the twelve reinforced concrete columns subjected to lateral and constant axial loads. The main experimental variables are concrete strength, the configuration of lateral ties, and the amount of lateral ties. Test results indicated that the steel configuration in column sections plays an important role in column behavior, and a proper configuration of lateral ties can obtain more ductile by the reduction of the space of lateral ties. Also, this experiment show that the utlization of high-strength concrete in columns properly designed on ACI Code takes less ductile. Therefore, we can conclude that the design of high-strength concrete columns under high axial loads requires more lateral ties than ACI Code.

• Journal of Korea Foundry Society
• /
• v.10 no.5
• /
• pp.408-416
• /
• 1990

The application of this new design approach called fracture mechanics allow one to determine the maximum allowable stress from the knowledge of the largest expected flow size and the plane strain fracture toughness of a material. In this study we examined the relation between retained austenite, mechanical property and fracture toughness accompanied by austempering heat treatment. Fracture toughness values and retained austenite volume were higher with the ADI(austempered ductile iron) which were austempered at $380^{\circ}C$ than austempered at $320^{\circ}C$. Additionally, fracture toughness values were increased for 1~2 hour austempering time but it was slowly decreased for 5 hour ADI maintaining the predominant fracture toughness($K_{IC}:83MPa{\sqrt{m}}$) is obtained following condition, namely, austempering temperature and time ($380^{\circ}C$ and 1 hour).

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.812-815
• /
• 2002

The shape of K-R curve for an ideally brittle material is flat because the surface energy is an unvaried material property. However, the K-R curve can take on a variety of shapes when nonlinear material behavior accompanies fracture. By the way, a general metallic material is nonlinear, structural steel is such. Therefore, the J-R curve form J-integral value instead of K parameters can be used to evaluate elastic-plastic materials with flaws in terms of ductile fracture that can be significant to design. In this paper, R-curve behaviors form K and J parameter is considered for the precise assessment of fracture analysis, in case of JS-SS400 steels.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2001.05a
• /
• pp.36-39
• /
• 2001

Tubular hydroforming has attracted increased attention in the automotive industry recently. In this study, a professional finite element program for analysis and design of tube hydroforming processes has been developed, called HydroFORM-3D, which is based on a rigid-plastic model. With the developed program several hydroforming processes such as a tee extrusion, an automotive rear axle housing and lower arm are analyzed and designed. And also, the Oyane's ductile fracture integral I was calculated from the histories of stress and strain according to every element and then the forming limit of the hydroforming process could be evaluated. The pediction of the bursting failure and the plastic deformation during typical hydroforming processes shows to be reasonable so that this approach can be extended to other various tube hydroforming processes.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2023.05a
• /
• pp.23-24
• /
• 2023

In this study, an easily recyclable separable glued-laminated timber (GLT)-steel beam was developed, and a structural design method was presented. The GLT and steel were mechanically composited using self-tapping screws. The GLT-steel beam was designed to fail in the compression of GLT. The bending moment and load-carrying capacity of the GLT-steel beam were predicted based on composite beam theory and compared with experimental test data. As a result, the GLT-steel beam exhibited ductile behavior, and compression failure of GLT was observed. The screw connection showed no damage while the steel plate was extended. The load-carrying capacity of GLT after failure was similar to the load resistance predicted by the compressive strength of GLT and the tensile strength of steel. This indicates that the ductile behavior of the GLT-steel beam can be safely designed by the tensile strength (yield) of steel.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.22 no.2
• /
• pp.181-187
• /
• 2009

After introduction of the earthquake resistant design code, it is required to achieve seismic performance of existing bridges as well as earthquake resistant design of new bridges. The achievement of seismic performance for existing bridges should satisfy the no collapse requirement based on the basic concept of earthquake resistant design, therefore, various methods with different strengthening scale should be suggested according to bridge types and importance categories. At present for typical bridges, most studied and applied strengthening methods are bearing change, pier strengthening and shear key installation for improvement of seismic performance. In this study a typical existing bridge, for which earthquake resistant design is not considered, is selected as an analysis bridge. Design changes are carried out to satisfy the no collapse requirement by way of the ductile failure mechanism and seismic performances are checked. It is shown that the seismic performance of existing bridges can be achieved by way of redesign of bridge system, e.g. determination of pier design section for substructure and change of bearing function for connections between super/sub-structure.

• Transactions of Materials Processing
• /
• v.9 no.3
• /
• pp.233-241
• /
• 2000

It is well known that the quality and efficiency of the design of metal forming processes can be significantly improved with the aid of effective numerical simulations. In the present study, a two-and three-dimensional finite element simulation system, CAMP form, was developed for the analysis of metal forming processes in the PC environment. It is composed of a solver based on the thermo-rigid-viscoplastic approach and graphic user interface (GUI) based pre-and post-processors to be used for the effective description of forming conditions and graphic display of simulation results, respectively. In particular, in the case of CAMPform 2D (two-dimensional), as the solver contains an automatic remeshing module which determines the deformation step when remeshing is required and reconstructs the new mesh system, it is possible to carry out simulations automatically without any user intervention. Also, the forming analysis considers ductile fracture of the workpiece and wear of dies for better usage of the system. In the case of CAMPform 3D, general three-dimensional problems that involve complex die geometries and require remeshing can be analyzed, but full automation of simulations has yet to be achieved. In this paper, the overall structure and computational background of CAMPform will be briefly explained and analysis results of several forming processes will be shown. From the current results, it is construed that CAMPform can be used in providing useful information to assist the design of forming processes.

• Geotechnical Engineering
• /
• v.9 no.3
• /
• pp.5-22
• /
• 1993

A series of laboratory tests (physical and mechanical index and engineering design) were conducted on undisturbed granite soils of CW and RS weathering grades in Korea. From these testes it can be concluded that most of physical and mechanical index values are very sensitive to change in weathering grade from CW to RS. Engineering design tests indicate that the unconfined compressive strength and the shear strength parameters are significantly reduced and that the soil becomes ductile and plastic with increasing weathering and saturation. It was found that weathered granite soils have the special characteristics when water saturated: (i) they significantly lose their shear strength(especially cohesion) and unconfined compressive strength, (ii) they are fragile and their grains break down in water as observed in grain size analysis.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.2 no.1
• /
• pp.136-141
• /
• 1998

It is demanded to obtain the design data for bond length of the strengthening carbon fiber sheets. An objectives of this study is to provide preliminary data of rational strengthening design method which is adequate to current domestic status. The present experimental study was performed to evaluate flexural strengthening effects of steel reinforced concrete beams strengthened with carbon fiber sheets. Following conclusions can be extracted. It is revealed that the maximum load carrying capacity is increased up to 9% when the reinforced concrete beams were strengthened with 1-ply of carbon fiber sheet which is half-width of beam. The performance of reinforced concrete sections were improved due to the strengthening carbon fiber sheets on the tensile side of beams. It is believed that the strengthening length of carbon fiber sheets must be provided as (0.5l+3d) to secure the ductile capacity of above three for the flexural strengthening of reinforced concrete beams.

• Structural Engineering and Mechanics
• /
• v.73 no.1
• /
• pp.53-64
• /
• 2020

In different high seismic regions around the world, many non-ductile existing reinforced concrete frame buildings, built without adequate seismic detailing requirements, have been damaged or collapsed after past earthquakes. The assessment and the retrofit of these non-ductile concrete structures is crucial theme of research for all the scientific community of engineers. In particular, a careful assessment of the existing building is fundamental for understanding the failure mechanisms that govern the collapse of the structure or the achievement of the recommended limit states. Based on the seismic assessment, the best retrofit strategy can be designed and applied to the structure. A school building located in Avellino province (Italy) is the case study. The analysis of seismic vulnerability carried out on the mentioned building has highlighted deficiencies in both static and seismic load conditions. The retrofit of the building has been designed based on different retrofit options in order to show the real retrofit design developed from the engineers to achieve the seismic safety of the building. The retrofit costs associated to structural operations are calculated for each case and have been summed up to the costs of the in situ tests. The paper shows a real retrofit design case study in which the best solution is chosen based on the results in terms of structural performance and cost among the different retrofit options.