On the basis of research results presented in Liu and Zhang(2005),the paper studies the influence on response of steel mega-frame structures from the secondary frame. Three representative steel mega-frame structures are selected as examples. Two analytical models are hypothesized for each example. Using finite element program, three-dimensional elastic time history analysis of three examples with different analytical models subjected to different earthquake waves are conducted. The results of structural period, displacement and internal forces including axial force, shear force and bending moment are obtained. Comparing these results between two models,some conclusions are obtained,which lay a foundation for further studying seismic performance and design of steel mega-frame structures.
