Dynamic Analysis And Comfort Evaluation Of Large-span Stages

Players dance with rhythm and make the stage structure vibrate under dynamic loads created by them. Once a footbridge was closed because the vibration caused by a marching army was too large. Though the loads created by dancers are relatively small, the vibration caused by dancers should not be neglected, especially to large-span stage. If the amplitude of vibration is too big, the service performance of stage will be influenced. Recently, lots of footbridges were complained not comfort enough or sometimes even dangerous to be used because the vibration was too large. The vibration of footbridges caused by people is concerned by structural engineering, bridge engineering and many other subjects. Vibration of footbridges and floors is standardized in every country by corresponding comfort index specification, according some of them, if the peak acceleration of footbridges and floors are controlled in a definite scope, the comfort level can be guaranteed. However, the vibration of large-span stage is seldom studied at present.Through the finite element analysis of large-span stage structure, the mechanical performance of stage under dynamic loads was studied. Because both stages and footbridges are large-span structures and can be simplified into simply supported beam, drawing lessons from the comfort evaluation of footbridge, the comfort level of stage is evaluated.Fixing the dynamic loads according to the Sweden code, dynamic analysis was applied to the stage. Drawing lessons from the comfort evaluation of footbridge, a reasonable method is acquired through the comparison, and the comfort level can be guaranteed when the density of players is controlled in a definite scope.The dynamic analysis shows both the stress and strain of stage members can satisfy the demand of design. Through the comparison of stress and vertical deflection, the static results are found more than 3 times of the dynamic results, and the method of using static loads to substitute for the dynamic loads in structure design is proved to be safe enough.In the past, the amplification coefficient, which is used to equal the dynamic loads with static loads, is decided by experiences. Through dynamic analysis and according to the demand of static design, reasonable scope of coefficient is put forward in this paper to control the design of single layer large-span stage with comfort level.Based on the analysis of single layer stage, the comfort level of double layer stage was studied. And the results can be used as a reference to arrange the distribution of players reasonably in the practical performance.