Electronic Thesis and Dissertation Repository


Master of Engineering Science


Civil and Environmental Engineering


Bartlett, Michael


The strength reduction factors, phi, defined in ACI 318-14 for different structural actions and elements lead to inconsistent results. This study proposes partial material strength reduction factors for concrete, phic, and reinforcing steel, phis, that yield similar design strengths and more consistent reliability indices. Three structural actions are investigated: moment; shear; and, combined moment and axial force. The first-order, second-moment method is used to compute reliability indices for moment and shear, and Monte Carlo simulation is used for combined moment and axial force. The statistical parameters assumed for the professional factor for shear strength significantly impact the reliability indices. Although no single combination of phis and phic is the best for these three actions, the recommended partial material strength reduction factors are phis of 0.90 and phic of 0.60, or for spirally reinforced columns, 0.70. Alternatively, for shear, the combination with phis of 0.80 and phic of 0.65 is recommended.