Title: Partial Material Strength Reduction Factors: for ACI 318?

Author(s): Tong Zhang and F. Michael Bartlett

Publication: Structural Journal

Volume: 116

Issue: 3

Appears on pages(s): 159-169

Keywords: beams; columns; design strength; moment; partial material strength reduction factors; reinforced concrete; reliability; slabs

DOI: 10.14359/51714475

Date: 5/1/2019

Abstract:
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.