Browsing by Author "Lee, Dongkeun"

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Development of improved exposed column-base plate strong-axis joints of low-rise steel buildings
(2020-06-01)
You, Young-Chan
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Lee, Dongkeun
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土木工程學系
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Department of Civil Engineering
Due to increasing seismic risk, seismic design has become mandatory even for low-rise structures in Republic of Korea since December 2017. However, it is not difficult to find undesirable exposed column-base plate strong-axis joints of low-rise steel buildings in the field. Such undesirable connections might not have sufficient capacity and stability under earthquake. Therefore, a series of experiments were carried out to develop improved exposed column-base plate strong-axis joints of low-rise steel buildings. In total, seven large-scale column-base plate strong-axis connection specimens were investigated under both axial compression and lateral cyclic loading. It was found that the hysteretic behavior of such improper joints typically used in the field was unstable due to a "rocking" phenomenon between a base plate and concrete foundation by large plastic residual deformation of anchor bolts. To overcome the rocking phenomenon, efforts were made to develop enhanced connections. Based on the test results, considerably improved and stable hysteretic behavior without the rocking phenomenon was obtained by using eight threaded anchor bolts. However, further study is needed to assess the effect of eight threaded anchor bolts on the seismic performances of more various connections. (C) 2020 Elsevier Ltd. All rights reserved.
Evaluation of Progressive Collapse Resistance of Steel Moment Frames Designed with Different Connection Details Using Energy-Based Approximate Analysis
(2018-10-01)
Lee, Sang-Yun
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Noh, Sam-Young
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Lee, Dongkeun
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土木工程學系
;
Department of Civil Engineering
This study evaluates the progressive collapse resistance performance of steel moment frames, individually designed with different connection details. Welded unreinforced flange-bolted web (WUF-B) and reduced beam section (RBS) connections are selected and applied to ordinary moment frames designed as per the Korean Building Code (KBC) 2016. The 3-D steel frame systems are modeled using reduced models of 1-D and 2-D elements for beams, columns, connections, and composite slabs. Comparisons between the analyzed results of the reduced models and the experimental results are presented to verify the applicability of the models. Nonlinear static analyses of two prototype buildings with different connection details are conducted using the reduced models, and an energy-based approximate analysis is used to account for the dynamic effects associated with sudden column loss. The assessment on the structures was based on structural robustness and sensitivity methods using the alternative path method suggested in General Services Administration (GSA) 2003, in which column removal scenarios were performed and the bearing capacity of the initial structure with an undamaged column was calculated under gravity loads. According to the analytical results, the two prototype buildings satisfied the chord rotation criterion of GSA 2003. These results were expected since the composite slabs designed to withstand more than 3.3 times the required capacity had a significant effect on the stiffness of the entire structure. The RBS connections were found to be 14% less sensitive to progressive collapse compared to the WUF-B ones.