Robustness of Load and Resistance Design Factors for RC Columns with Wind-Dominated Combination Considering Random Eccentricity

Abstract

Based on the capacity models in the 2008 edition of the American Concrete Institute (ACI) Standard Building Code Requirements for Structural Concrete, a more realistic limit state function is built for reinforced concrete columns with random eccentricity. Then, we discuss the applicability of the load and resistance factors in the code, which is mainly based on reliability calibrations with a fixed eccentricity criterion. Taking the wind-dominated combination as an example, representative cases are established by selecting typical values of four related design parameters. Using the load and resistance models in previous reliability calibration of the code, the probabilistic distribution of eccentricity and the statistics of column resistance are analyzed for each case. The analysis indicates that the possible eccentricity shows a scatter over a large range, and the probabilistic model of column resistance varies from case to case, which is largely different from the constant resistance model assumed in previous reliability calibration. With Monte Carlo simulation (MCS), the column reliability is calculated and obtained for different cases. The results show that the fixed eccentricity criterion underestimates the reliability differences among cases and overestimates the column reliability in some tension failure cases. To attain a robust design, an improved measure is recommended by selecting optimum wind load factors varying with cases. The new calibration results prove that the recommended measures can achieve the goal better.