Study on upgrading of functional maintenance performance for cable racks

Abstract

In industrial facilities, air conditioning and wiring equipment is often installed in suspended structures. The Tohoku (March 2011) and Kumamoto (April 2016) earthquakes caused significant damage not only to buildings but also to equipment within them. Cable racks, one of the wiring facilities, consist of cable trays that carry cables and fully threaded bolts that support them. Considering the load-transfer circuit of a cable rack during an earthquake, the stresses acting on the ends are relatively high because of their long length and small cross-sectional area. In general suspension structures, the cable tray is directly connected to the ceiling with suspension bolts. In this structure, the seismic force input from the ceiling does not act directly on the upper end of the all-thread bolt compared to the general all-thread structure due to the rotation of the ball joint. The ball joint is also installed at the lower end, so that seismic forces input to the ceiling do not act directly on the cable tray. To verify the effectiveness of the proposed structure, vibration tests were conducted using full-scale cable racks to compare and verify the vibration characteristics of the conventional and proposed structures. As a result, this system allows cable racks to improve the seismic resistance regardless of the loaded mass of the cable racks in both cases of steady and unsteady inputs.