The effect of mechanical and geometric uncertainty on perforated CFS bracing members

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In the capacity design of cold-formed steel frames with X diagonal bracings, the ratio of overstrength to slenderness is particularly critical. The diagonal elements of these braces may be fabricated with perforations at the brace ends to satisfy design and detailing requirements for capacity protection of frames with concentric X bracings. In the paper, the influence of stochasticity in the geometrical features and mechanical properties on the overall structural response of specific cold-formed steel perforated elements is assessed. The impact of statistical variation in design parameters on the yield strength, ultimate strength, and ductility is evaluated through a Monte Carlo simulation. Variability in member geometric features was determined from current design specifications, while variability in steel mechanical properties was determined via experimental testing. Monte Carlo simulations indicate a slight reduction of yield and ultimate member resistance increasing the number of holes. A normal probability distribution function, with a skewness greater than zero, which increases with a larger number of holes, characterizes both the yield and ultimate strength histogram. The work concludes providing recommendations for designers to promote utilization of perforated braces in seismically-active areas