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Kim S.-B.,Naeun Structural Engineering Co. | Kim S.-S.,Korea University of Technology and Education | Shim H.-J.,Hyundai Steel
International Journal of Steel Structures | Year: 2014

Since Euler's classical theory, which he proposed in 1759, many column curve formulations have been proposed. This study investigates the flexural buckling strength (F cr ) calculated using the allowable stress design specification and the load and resistance factor design (LRFD) specification of the American Institute of Steel Construction. It is noted that the exponential function of the column curve formulation using LRFD is difficult to use in practice. Therefore, a simple parabolic function is proposed for the inelastic buckling strength of a steel column loaded with uniaxial compression, and it is shown to be consistent with many design codes. The expressions for inelastic buckling strength formulation as defined previously for ASD are used here. To verify the proposed equation, 118 individual test results of steel columns are examined. The mean of the ratio of the column strength to the proposed flexural buckling strength is 1.089, indicating that the proposed strength curves are in good agreement with the test results. © 2014 Korean Society of Steel Construction and Springer-Verlag Berlin Heidelberg. Source


Shim H.-J.,Hyundai Steel | Lee E.T.,Chung - Ang University | Kim S.-B.,Naeun Structural Engineering Co. | Kim S.-S.,Korea University of Technology and Education
International Journal of Steel Structures | Year: 2014

This paper reports a new beam-to-column connection that is suitable for use in the weak axis of a column. The proposed system mainly uses bolts, and it minimizes the use of welding, which is generally difficult to perform onsite. In this system, an H-shaped steel beam is joined to an H-shaped steel column by bolted splices at the top flange and without a scallop at the web. Eight specimens were tested to verify the structural performance of the developed connection; in doing so, the effects of geometry and arrangement of the plate were also considered. The connection materials required and CO2 emissions were estimated to evaluate the cost-effectiveness of the proposed system. The obtained results showed that this system was suitable had better structural performance than standard weak-axis connections and excellent constructability, making it suitable for replacing existing bracket-type weak-axis connections. © 2014 Korean Society of Steel Construction and Springer-Verlag Berlin Heidelberg. Source


Park H.-G.,Seoul National University | Lee H.-J.,Seoul National University | Choi I.-R.,POSCO | Kim S.-B.,Naeun Structural Engineering Co. | Park S.-S.,Shinsegae EandC
Journal of Structural Engineering (United States) | Year: 2015

An experimental study was performed to investigate the axial-flexural load-carrying capacity of concrete-filled steel tube columns encased with thin precast concrete (PC). Six eccentrically loaded columns and one concentrically loaded column were tested. To prevent the premature failure of the concrete encasement, various reinforcement details such as studs, steel fiber, welded wire mesh, and cross ties were used. The maximum axial loads of the specimens agreed with the strengths predicted by current design codes, although in some specimens, the load-carrying capacity decreased immediately after the peak strength owing to early spalling of the concrete encasement. On the basis of the test results, the use of fiber-reinforced concrete is recommended to increase the ductility of columns by restraining the spalling of the concrete encasement. © 2015 American Society of Civil Engineers. Source


Lee H.-J.,Seoul National University | Park H.-G.,Seoul National University | Park S.-S.,Shinsegae EandC | Kim S.-B.,Naeun Structural Engineering Co. | Choi I.-R.,POSCO
Journal of Structural Engineering (United States) | Year: 2016

A cyclic loading test was performed to investigate the seismic performance of exterior beam-column joints of concrete-encased-and-filled steel tubular (CEFT) columns. Two specimens with steel beams and two specimens with precast concrete (PC) beams were tested under cyclic loading. The dimensions of the column cross section were 670×670 mm, which was a two-thirds-scale model of the prototype column. The test parameters for the steel beam and the PC beam were the beam depth (488 and 588 mm) and the flexural rebar ratio (1.1% and 1.5%), respectively. In the steel beam-CEFT column joints, continuity plates were used, while in the PC beam-CEFT column joints, couplers were used for the rebar connection. The steel beam-column connections failed due to early fracture of the continuity plate, and the PC beam-column connections failed due to rebar buckling and concrete spalling after beam yielding. The strength of the steel beam-column connections was evaluated using an existing design method, and the seismic performance of the PC beam-column connections was evaluated. On the basis of the test results, design considerations for beam-CEFT column joints were recommended. © 2015 American Society of Civil Engineers. Source

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