Young-Suk Oh

Hysteresis behavior of CFT column to H-beam connections with external T-stiffeners and penetrated elements

This paper is a study on concrete-filled tubular (CFT) column to H-beam welded connections that are reinforced externally with T-shaped stiffeners at the junction of the column and beam, and with a reinforcing bar or bent plate which penetrates a column. Cyclic loading tests on eight cruciform connections and finite element analysis using ABAQUS were carried out. The results of the tests demonstrate that an increased stiffener length was more effective than an increase in the area of penetrated elements for the criteria of both strength and stiffness. Also, good agreements between analytical results and experimental tests are found. By reinforcing external T-stiffeners, the connection moments of all specimens exceed the beam full plastic moment and stable hysteresis behavior under cyclic loading is shown.

An Experimental Study on the Flexural Behavior of RC Beams Strengthened with High-Strength Bars(1)

This paper outlines a new strengthening technique for concrete beams using externally unbended high-strength bars. The advantages of proposed method lie in speed and simplicity of construction compared to the alternative strengthening method. Externally unbended reinforcement retains many of the advantages over external unbended prestressed tendons. It eliminates time consuming stressing operations. Clearance requirements around anchorages are reduced as access is not required for prestressing jacks. Test results of eight specimens on reinforced concrete beams using different reinforcement materials such as carbon fiber sheet, steel plate and high-tension bar are reported. The beam strengthened by carbon fiber sheet showed a brittle failure mode due to the separation of fiber. As a result of draped profile of external bar, the maximum strength of the beam were increased by up to 212 percent and the deflections were reduced by up to 65 percent. Test results show that the beams reinforced with high-tension bar are superior to reference specimens, especially for the strength and deformation capacity.

Experimental Investigation of Composite Moment Connections with External Stiffeners

This paper presents tensile behavior for Concrete-Filled Tubular (CFT) column to H-beam welded connections. These connections were reinforced externally with T-shaped stiffeners at the junction of column and beam. Tensile loading tests and analyses were carried out for the T-stiffener connections. The results demonstrated that the overall behavior and failure modes of all the specimens were governed mainly by the horizontal stiffeners rather than by the vertical stiffeners, while the vertical stiffener only played a role in transferring the load introduced from beam to column. In addition, a simple design method for the T-stiffeneris suggested, with consideration of the effects of the shear strength of the horizontal stiffener and yield line mechanism of the column flange. The prediction and test results are compared and they are in good agreement.