Influence of Center-Hung Scoreboard on Seismic Response of Space Truss Structure under Vertical Earthquake

The center-hung scoreboard is a large-scale display device flexibly suspended in the center of the roof of the gymnasium. It is generally heavy, but the influence law of center-hung scoreboard on dynamic characteristics and seismic response of the space truss structure is unknown. In this paper, dynamic characteristics and seismic response under vertical seismic input of two coupled systems that are comprised of the space truss structure and the center-hung scoreboard is analyzed by using dynamic explicit method with Abaqus software. The influence of the sling length and the scoreboard weight on the seismic response are investigated. Due to the use of flexible slings, the vibration of the overall structure is divided into two types including the vibration of the center-hung scoreboard itself in the first three modes and the vibration of the overall structure by the combination of the center-hung scoreboard and the space truss structure in the fourth and following modes. The mode shapes of the fixed mass model are always expressed as the vertical vibration of the space truss structure. The peak acceleration of some top nodes and some bottom nodes in the flexibly suspended model can be two and three times of those in the fixed mass model, respectively. The axial force of some top chords, web members and bottom chords in the flexibly suspended model can reach 3.6 times, 9.8 times and 1.8 times of that in the fixed mass model, respectively, under specific combination of the weight and the length. It is concluded that influence of the center-hung scoreboard on the seismic response of the space truss structure should not be ignored, otherwise the seismic response is likely to be seriously underestimated. The deep reason is that the unsynchronous vertical movement between the space truss structure and the center-hung scoreboard will cause vertical impact effect.