The analysis model under multi⁃support excitation was established based on the absolute displacement method. The multi⁃support non⁃stationary ground motions were artificially synthesized by trigonometric series method.A square and a rectangular multi⁃support truss models with span of 90 m were selected,and the dynamic response of the two structures under uniform excitation and multi⁃support excitation were respectively analyzed.Base isolations were adopted at the bottom of the two models,and the differences of structures′ response before and after isolation were investigated through time history analysis.Results showed that the axial forces of control bars vary little under uniform excitation while they change largely under multi⁃support excitation, under the horizontal earthquake action. The maximum accelerations of truss nodes of the square structure increase under multi⁃support excitation, but the rectangular structure was opposite.It means the internal forces results were unreliable if uniform excitation was directly used in long⁃span strictures. The responses of the isolated structures were greatly reduced compared with non⁃isolated ones, and the regularities were almost consistent under multi⁃support excitation or uniform excitation.Under the vertical earthquake action,axial forces and the moments of the non⁃isolated square structure increased a little under multi⁃support excitation compared to uniform excitation,but the rectangular structure increased more.The axial forces of isolated structures raise instead under uniform excitation. Therefore,the spatial effect of seismic action should be more considered when structures used the vertical seismic action.%基于绝对位移法建立了多点输入分析模型，采用三角级数法人工合成多点非平稳地震动。选取90 m跨度的正方形及长方形多点支承网架为研究对象，分别对两大跨结构进行一致和多点地震动输入下的动力反应分析。采用基础隔震，通过时程分析研究隔震前后两结构的响应规律差异。结果表明：在水平地震作用下，未隔震模型在一致输入下上部网架各杆件最大轴力相差不大，而在多点输入下相差较大；正方形结构上部网架节点最大加速度响应在多点输入下增大，而长方形结构却相反；隔震后结构响应有了大幅度的减小，多点输入与一致输入轴力响应规律几乎一致。在竖向地震作用下未隔震正方形结构在多点输入下的杆件轴力与支承柱柱底弯矩，与一致输入相比均有所增大，其中长方形结构增幅更大；隔震后结构在一致输入下轴力响应反而增大，可见竖向地震作用时应多加考虑地震动空间效应。
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