Papers by Author: Hak Eun Lee

Abstract: The axial stiffness of the corrugated steel plate is negligible by nature of unique geometric characteristics of the plate called as the accordion effect. This unique effect results in high efficiency on post-tensioning. Thus, corrugated steel plate is very suitable for a web of PC-box girder. Recent researches show that strain and stress in sub-panel of corrugated steel webs, that are induced by local bending of the sub-panel, exist even if the axial stiffness is negligible. These strain and stress in sub-panel are important since it might cause fatigue failure of the structure under repeated loading. This study presents the analytical simulation of the accordion effect of the I-girder with corrugated steel webs under pure axial load or bending including the effect of local bending of sub-panel of the corrugated steel webs. Theoretical study and numerical results were combined to develop the simplified equation to evaluate the accordion effect including the effect of local bending of the sub-panel.

Abstract: Rectangular concrete-filled tubes (RCFTs) have been widely used as columns of building and bridge piers due to several advantages such as their strength-to-size efficiency and facilitation of rapid construction. Recently, some researchers have tried to use RCFT as a wall system in a building. RCFT wall have a high aspect ratio while the aspect ratio of the RCFT column is usually one. Thus, the behavior of the RCFT wall is clearly different from that of RCFT column and it needs to be investigated. In this study, the axial behavior of the RCFT wall was investigated through analytical simulation, and the effects of the aspect ratio, internal stud, and through rebar on axial behavior of the RCFT wall were examined. From the results, it was found that axial load capacity is decreased with increasing aspect ratio due to local buckling of the steel tube, and this local buckling can be efficiently prevented by using internal through rebar.

Abstract: For I-girder with high strength steel, it is known that the flexural ductility is considerably decreased by increasing the yield strength of material. Thus, it is necessary to conduct a study for guaranteeing proper flexural ductility of I-girder with high-strength steel. In this study, the evaluation of flexural ductility of negative moment region of I-girder with high strength steel where yield stress of steel is 690Mpa is presented based on the results of finite element analysis and experiment. From the results, it is found that the flexural ductility of the I-girder is significantly reduced due to the increase of elastic deformation and the decrease of plastic deformation ability of the material when the yield strength increases. This study proposed equation predicted flexural ductility of high strength steel in negative moment region. It is also proposed the method to improve the flexural ductility by an unequal installation of cross beam and an optimal position of cross beam. Finally, the effects of the unequal installation of cross beam on the flexural ductility are discussed based on the finite element results and the experimental results.