Analysis on column-bracing forces considering random initial imperfections

ZHAO Jin-you^1,2, ZHANG Yao-chun³

1.College of Civil Engineering,Northeast Forestry University,Harbin 150040,China;2.Institute of Engineering Mechanics,China Earthquake Administration,Harbin 150080,China;3.School of Civil Engineering,Harbin Institute of Technology,Harbin 150090,China



Abstract:

A large number of column-bracing systems were modeled and analyzed by second-order analysis using finite element program ANSYS,in which the random combination of the initial imperfections between columns and horizontal braces was well considered by Monte Carlo Method.According to the analysis results,four kinds of instability modes of column-bracing systems were found,the probability density function of the mid-height horizontal bracing forces was established based on probability statistics,and the design bracing forces were also obtained.The results indicated that the above design bracing forces are smaller than that proposed by the "Code for design of steel structures"(GB50017-2003) when the top axial compressions on the braced columns are equal,and much smaller than the latter when the top axial compressions on the braced columns are unequal.The results also indicated that the random combination of the initial imperfections between columns and horizontal braces leads to the randomness of the mid-height horizontal bracing forces in compression or in tension,so that the design bracing forces can be reduced.

Key words:  column-bracing system  bracing forces  Monte Carlo Method  initial imperfection  random combination

DOI：10.11916/j.issn.1005-9113.2011.02.024

Clc Number:TU311

Fund: