# Performance Evaluation of Rigid Braced Indirect Suspended Ceiling with Steel Panels
## 2 Experimental Program
### Test Setup and Test Protocol  
The steel frame for the test on which the ceiling system was installed was 4 m wide and 4 m long, and its primary natural frequency (\(f_{n}\)), as estimated through the structural analysis program, Midas gen, was 25 Hz in the x-direction and 32 Hz in the y-direction.  
ICC-ES AC156 [10], which is the test standard for nonstructural elements, suggests that the experimental frame should have adequate rigidity to avoid resonance with the nonstructural elements and to transmit the floor vibrations to nonstructural elements. The results of the shaking table test confirmed that the steel frame transmitted floor vibrations to the ceiling material. Figure 8 shows the steel frame that was used in the shaking table test.  
For the specimen that the brace was applied to, an accelerometer was installed, as shown in Figure 9, to measure the response of the specimen during an earthquake. For this investigation, 11 accelerometers were installed in each direction: one at the center of the shaking table surface, five at the top of the test frame, and five on the ceiling surface.  
Figure 6: Brace installation of the specimens: (**a**) plan view of Seismic Design applying Brace 2 unit (SDB-2) and (**b**) plan view of Seismic Design applying Brace 3 unit (SDB-3).  
Figure 7: Installation of brace reinforcement member in SDB-3: (**a**) rigid brace member, (**b**) hanger for 2-direction brace, (**c**) hanger for reinforcement member, (**d**) reinforcement member.  
Four displacement meters were installed so that the displacement of the ceiling and test frame could be measured with respect to the two-way axis. The plan with the vibration band was established in accordance with ICC-ES AC156. Artificial seismic waves were first generated on the \(x\)-axis for two-way retention, and artificial seismic waves on the \(y\)-axis were redesigned to avoid the x-direction and resonance. In accordance with KDS 41 17 00, the short-period design spectral response acceleration (\(\mathrm{S_{DS}}\)) was 0.54 g (seismic zone II, ground condition), and the height z of the nonstructural element installation was assumed to be the same as h. \(\mathrm{A_{FLX\text{-}H}}\) was calculated as 0.864 g and \(\mathrm{A_{RIG\text{-}H}}\) was determined to be 0.648 g according to the equation below. From this, EQ100% was formed, and the acceleration level of the artificial seismic wave increased in stages, which confirms the damage status of the ceiling system.  
\[\mathrm{A_{FLX\text{-}H}}=\mathrm{S_{DS}}\left(1+2\ \mathrm{z/h}\right)=0.54\ \mathrm{g}\times(1+2)=1.62\ \mathrm{g}<\mathrm{A_{FLX\text{-}H\text{,}Max}}=1.6\mathrm{S_{DS}}=0.864\ \mathrm{g} \tag{1}\] \[\mathrm{A_{FLX\text{-}H}}=0.864\ \mathrm{g} \tag{2}\]  
Table 3 lists the artificial seismic wave levels applied in the test, and Figure 10 shows the test response spectrum (TRS) in Test 2 (0.864 g) that was measured on the shaking table surface (A1) for the SDB-2 specimen.  
Figure 10 shows the test response spectrum (TRS) and the required response spectrum (RRS) for each direction of the shaking table surface (A1). The TRS is located in the RRS of 90% or more and 130% or less on the graph. This means that the artificial seismic wave was designed to satisfy the AC156 standard, and the experiment was conducted. The TRS refers to the acceleration response spectrum of the time history data that were measured by an accelerometer attached to the surface of the shaking table.  
Figure 8: Test frame for shaking table test.  
Figure 9: Accelerometer installation locations for the brace specimens: (**a**) base of the seismic table, (**b**) top frame (roof), (**c**) and ceiling surface.