Suspended Building System Performance Analysis, The Vertical Seismic Action

Vertical seismic action has become a more and more important subject to engineers in recent decades. The earthquake macro-phenomena have demonstrated that the influence of the vertical seismic motion is obvious in high intensity area. As a new architectural system in recent years, the suspended structure should be considered the effect of the vertical seismic action.It can be more effective than traditional structure in seismic resistance.In many references suspended structure is modeled as "story model", while analyzing the response of the buildings due to the seismic excitation. This model has more suitability in the analysis of the horizontal seismic action on suspended structure. However, to the structure under vertical seismic action, the postulate that each column has the same displacement in the same floor is impossible confirmation. Furthermore, in the story model, the computational results only reflect the change of the axial forces of the columns due to vertical seismic action, but it can't reflect the change of the internal forces due to vertical seismic action.So,it's necessary to establish a new computational model for the vibration analysis due to vertical seismic action.The paper presents a new model——the series-parallel-connection model withconsidering joint rotation on suspended structure effected by vertical seismic force, and the mass matrix is established using the method of consistent mass. The dynamic matrix of structure is predigest through dynamic force condensing, the coupling relationship of vertical displacement and rotation is eliminated. Therefore, the degree of dynamic matrix is lowered.The stiffness matrix of suspended structure due to vertical seismic action considering joint rotation is deduced. There are also vertical vibrational mode analysis and elastic time-history analysis on the model effected by different vertical seismic force through the predigested matrix in the paper.At the same time we can educe some dynamic response characteristics of suspended structure to vertical earthquake action,and it's valuable to engineering design.