Differential Column Shortening Effects in Typical Medium- to High-rise Buildings

摘要

Differential column shortening in a building structure causes axial force redistribution among columns and walls, and introduces additional forces in the horizontal members such as beams and slab. Thus, it needs to be considered in the design, especially for medium to high-rise buildings. Extensive research has been conducted to investigate this phenomenon [Fintel and Khan 1969 and 1971, Banavalkar and Wilkerson 1993, Gosh 1996, and Maru et al. 2001, among others]. It has been shown that differential column shortening is affected by the relative axial stiffness and the tributary area of columns and walls. Moreover, the ratio between beam and column stiffness and the construction sequence also have significant influence on the axial force redistribution.The best way to illustrate differential column shortening phenomenon is to conduct floor-by-floor analysis, generally known as construction sequence analysis. To this end, several methods have been proposed and commercial software is available [Choi and Kim 1985, Maru et al., 2001, Maru et al., 2003, Sharma et al., 2004]. However, to the knowledge of the authors no general conclusions appropriate for design practice have been drawn regarding differential column shortening behavior in typical medium- to high-rise buildings. General building codes do not give a specific guideline about when and how differential column shortening should be considered. Consequently, this issue is usually left to the judgment of structural engineers. Aimed at providing structural practitioners with a guideline to determine how important the differential column shortening behavior may be for a typical building system, a systemic study is conducted and reported in this paper. First, typical structural systems for medium- to high-rise buildings are identified. Next, using construction sequence analysis method, studies are conducted to investigate the influence of the variation of controlling parameters such as floor levels and beam to column stiffness ratio to the effects of differential column shortening.. The results obtained in this research can serve as an aid to the structural engineers during schematic design.