This study proposes an effective steel frame modular system and evaluates the structural performance of its beam-column connection through experimental and analytical work. The new steel frame modular system utilizes the blind bolts, which allow free access to the structural members of the closed cross-section. In addition, the new modular system is designed such that the strength of its beam members is considerably lower than that of its column members to implement the strong column-weak beam concept. In order to investigate the effectiveness of the proposed modular beam-column connection, two types of specimens were designed and tested. One of the two specimens has four knee brace members to increase the bending stiffness of the connection, while the other does not have these components. The applied load versus displacement curves are plotted for the two specimens, and their failure modes are identified. Finally, a simplified analytical model for the modular beam-column connection is proposed, and its effectiveness is validated by performing its push-over analysis and comparing its results with the test results.

In Korea, the earthquakes in Gyeongju (2016) and Pohang (2017) have led to increased interest in the seismic design of nonstructural elements. Among these, the suspended ceiling can cause personal injury and property damage. In addition, most suspended ceilings that are used in Korea neither have seismic design details nor meet the current seismic design standards. There are two seismic design methods for suspended ceilings using a perimeter clip and a brace. In the United States and Japan, seismic design of ceilings is typically used, but the concepts of applying and installing braces are different. This is because the typical ceiling systems are different in the United States and Japan. In this study, a brace-applied ceiling system that is suitable for a suspended ceiling with a steel panel was applied in the indirect suspended ceiling mainly used in Korea. In addition, the seismic performance was verified through a shaking table test. All the specimens were applied with anti-falling clips that are designed to prevent the panels from falling, and they satisfy KDS 41 17 00, which is a Korean seismic design life safety standard. Without considering these factors, the performance level is lower than a nonseismic designed ceiling, which is not properly designed or constructed.

Studies on the constructability of cold-formed steel (CFS) members are lacking. In this context, this paper proposes an integrated panel to replace the studs and steel sheet in the steel-sheathed wall system used in light gauge steel frames. The integrated panel was developed, to not only exhibit better structural performance and constructability than the steel-sheathed wall system, but to also reflect the appropriate details for applications to on-site panel construction. Cyclic loading tests were performed to investigate the seismic performances of three integrated panel specimens and a steel-sheathed panel specimen. The integrated panel specimens exhibited greater deformation capacity, ductility and equivalent damping ratio than the steel-sheathed panel. Although the web slenderness of the integrated member was nearly 400, the nominal strength of the integrated panel was predictable on an AISI standard. However, for stud-reinforced integrated panels, the nominal strength was overestimated by 45%–60%, and a draft equation was proposed to predict the yield strength of these panels. The proposed equation accurately predicted the yield strength of the stud-reinforced integrated panel specimens. The study results can aid in the construction of light gauge steel frames that require reinforcing parts with a high web slenderness ratio.

This paper proposes a new steel concrete composite beam that has a similar shape to the conventional steel wide flange beam, but whose lower flange has a tubular shape with infilled concrete. It has openings in the web for perfect integration between concrete and steel materials, and the tubular lower flange is reinforced with steel rebars to enhance its flexural strength. The bending capacity of the new composite beam was investigated by performing a two-point loading test on seven specimens, which can be categorized mainly into two types, non-composite and fully composite specimens. The load versus displacement curves were plotted for all the specimens and their failure modes were identified. Theoretical equations were proposed to estimate the flexural strength of the new composite beam members, and their accuracy was examined by comparing the predictions of the equations with the test results.