Title: Partial Material Strength Reduction Factors: for ACI 318?
Author(s): Tong Zhang and F. Michael Bartlett
Publication: Structural Journal
Appears on pages(s): 159-169
Keywords: beams; columns; design strength; moment; partial material strength reduction factors; reinforced concrete; reliability; slabs
The strength reduction factors, , 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, c, and reinforcing steel, s, that yield similar design strengths and more consistent reliability indexes. Two structural actions are investigated: moment, and combined moment and axial force. The first-order, second-moment method is used to compute reliability indexes for moment, and Monte Carlo simulation is used for combined moment and axial force. The recommended partial material strength reduction factors are s of 0.90 for slabs, beams, and both tied and spirally reinforced columns, and c of 0.60 for slabs, beams, and tied columns or 0.70 for spirally reinforced columns.