# Performance Evaluation of Rigid Braced Indirect Suspended Ceiling with Steel Panels
## 2 Experimental Program  
### Design of Test Specimens  
As shown in Figure 3a, most of the ceiling systems that are applied in Korea use indirect suspended ceilings are composed of hanger bolts, carrying channels, a main T-bar, and a cross T-bar. The connections between the members are a hanger, carrying channel/T-bar clip (C/T clip), and a connection in the grid between the T-bars. The hanger connects the hanger bolt and the carrying channel, and the C/T clip connects the carrying channel and the T-bar. The panels that are used in the T-bar system are mostly ceiling systems with nonadhesive ceiling panels and can be classified into three types, as shown in Figure 3d-f. All three types can be classified as non-adhesive ceiling panels. Figure 3f is the most widely used lay-in type, which is mounted on a T-shaped grid member for construction. As depicted in Figure 3e, this is a clip-in type, and it is constructed by inserting a panel into a member, forming a grid. The members forming the grid that used the clip-in type were manufactured so that the panels could be inserted. Figure 3d shows the type of steel panels that were used in this study. The panel is inserted into the T-shaped grid member, and the panel is manufactured so it can be fitted into the grid member. In Korea, ceiling systems with steel panels are mainly used in large spaces with high floors and large ceiling areas. In addition, they are developed with a focus on the ease of maintenance and construction. If these steel panels fall during an earthquake, personal injuries may occur because of the high floor height and panel weight. Figure 4 shows the concept of the brace system that was used in this study. In  
Figure 3: Suspended ceiling system with steel panel in Korea (indirect suspended ceiling). (**a**) Suspended ceiling system with steel panel, (**b**) hanger and carrying channel/T-bar clip (C/T clip), (**c**) anti-falling clip, (**d**) insert type of panel, (**e**) clip-in type of panel, (**f**) and lay-in type of panel. order to apply the brace in two directions for an indirect suspended ceiling, it should be applied using a hanger bolt, a carrying channel, and a hanger to form the connection. This study applied the existing research and products to the direct suspended ceiling and they are not consistent with the situation in Korea. It was newly developed for an indirect suspended ceiling. The shaking table test consisted of two specimens, and it was performed with variables such as the end clearance, molding width, and brace spacing on the steel frames with a ceiling installation area of 3.8 m \(\times\) 3.8 m. According to the MLIT Notice No. 771, the seismic designed ceiling applying brace (2 units) (SDB-2) specimen was applied with an end clearance distance of 60 mm and a molding width of 90 mm. In addition, mechanical jointing was performed on the C/T clip and the hanger. For the seismic designed ceiling applying brace (3 units) (SDB-3) specimen, a molding width of 50 mm and an end clearance distance of 25 mm were used. Mechanical jointing was performed for the C/T clips and hangers, and a specially designed main T-bar-cross T-bar connection was used to perform mechanical jointing. The un-seismic designed ceiling (USD) is a test specimen that has not been subjected to a seismic design that applies the details of a steel panel in Korea. It does not have mechanical joints and is characterized by a narrow molding width for aesthetic reasons. The USD was analyzed in a previous study [8] that was used as a comparative specimen for the experiment in this study. Table 2 lists the variables that were checked for each test subject. In the case of the brace and hanger bolt connector, which was used in SDB-2, it is joined to the brace with bolts, but it can easily yield because of its long and thin shape. The connector that was used in SDB-3 was developed by supplementing this easily yielding shape and it was joined to the brace by using screw bolts.