Abstract
The horizontal bracing forces of column-bracing systems derived from past studies and current design codes were considered only located at middle of columns. Actually, the horizontal braces used to reduce the out-of-plane effective column lengths are frequently designed not to locate at middle of columns. In this paper, a large number of column-bracing systems with the horizontal braces unlocated at middle of columns were modelled and analyzed using the finite element method, in which the random initial geometric imperfections of both the columns and the horizontal braces unlocated at middle of columns were well considered by the Monte Carlo method. Based on the numerical calculations, parametric analysis, and probability statistics, the probability density function of the horizontal bracing forces was found, so that the corresponding design forces of horizontal braces unlocated at middle of columns were proposed which were compared with the design mid-height horizontal bracing forces in the previous study and the relevant codes. The results indicate that the design forces of the horizontal braces located at 0.6 column height are smaller than the mid-height horizontal bracing forces in the previous study while the design forces of horizontal braces located at 0.7 column height are larger than the mid-height horizontal bracing forces in the previous study. The proposed design forces of the horizontal braces located and unlocated at middle of columns are both smaller than the mid-height horizontal bracing forces stipulated in GB50017-2017, Eurocode 3-1992, and AS4100-1998. The above conclusions provide references for the engineering applications and further related code revisions.
Highlights
One of the most important functions of bracing members in structural systems is to provide intermediate lateral support to compression members for enhancing their stability [1]. e brace strength requirements to achieve a specified increase in the buckling strengths of the braced columns have generally been developed from a single column-brace model [2,3,4] to column-bracing systems [5,6,7,8]
A large number of column-bracing systems with the horizontal braces unlocated at middle of columns have been carried out by second-order analysis using ANSYS, in which the initial geometric imperfections of both the columns and the horizontal braces were randomly sampled according to the Monte Carlo method
The probability density function of the design forces of the horizontal braces unlocated at middle of columns was found by probability statistics, so that the corresponding design forces of the horizontal braces unlocated at middle of columns were proposed which were compared with the design mid-height horizontal bracing forces in the previous study and the relevant codes
Summary
One of the most important functions of bracing members in structural systems is to provide intermediate lateral support to compression members for enhancing their stability [1]. e brace strength requirements to achieve a specified increase in the buckling strengths of the braced columns have generally been developed from a single column-brace model [2,3,4] to column-bracing systems [5,6,7,8]. In past studies on the mid-height horizontal bracing forces for column-bracing systems [7, 8], the random initial geometric imperfections of both the columns and the horizontal braces were well considered by the Monte Carlo method. Erefore, in order to estimate and to ensure the accuracy of the design forces of the horizontal braces unlocated at middle of columns, it is still necessary to Advances in Civil Engineering consider the effects of uncertainties of initial geometric imperfections [9]. A large number of column-bracing systems with the horizontal braces unlocated at middle of columns have been carried out by second-order analysis using ANSYS, in which the initial geometric imperfections of both the columns and the horizontal braces were randomly sampled according to the Monte Carlo method.
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