By analysing the characteristics of the single-section blasting vibration, this paper analyzes the relationship of the vibration superposition and influential factors, and indicates the attenuation of blasting seismic wave propagation in rock mass is the main reason which vibration superposition in middle and far field is generated.

The mode superposition method is used in the dynamic calculation.

In this paper, the internal forces in the composite space grids were calculated by using the mode superposition response spectrum method and the pattern of the internal forces in those structures under vertical earthquake, the problem of truncated modes and the feature about the distribution of the vertical seismic force coefficient were studied.