The exact behavior of multistory building is a matter of concern and interest in the structural engineering. There are two important facts that have very significant effects on the accuracy of the analysis but are seldom considered in the most of the analysis programs for building structures. They are as follows:(1) The frame stiffness matrices are assembled after individual condensation under the assumption that the stiffness matrices of each frame are uncoupled one another; and (2) the whole building is built up in one step and the loading conditions are applied after the completion of the frame construction. But a multistory building is built up not in one step but in as many steps as its story numbers. Accordingly, the dead loads must be applied through all construction steps, while the live loads may be applied after the completion of the frame construction.
This paper is composed of three parts. First of all, three dimensional analysis program is proposed to avoid the errors of the existing ones. Using this program, the effect of sequential application of dead loads due to the sequential nature of construction is examined closely. Finally, two simplified approaches, termed as Correction Factor Method and Correction Force Method, to solve the problem without elaborated step by step analyses are proposed. Correction Factor Method utilizes the correction factors established by regression from the data obtained from the existing buildings to modify the results from the ordinary analysis to produce more accurate solutions, while the Correction Force Method applies the correction forces obtained by the frame flexibility matrix based on the idea that differential column shortenings are approximately zero at the top floors of the building. Some numerical tests are presented to show the validity and effectiveness of each method.
