Abstract

In the design of reduced beam section (RBS) moment frame connections, the peak connection strength factor (𝐶𝑝𝑟) is used to estimate the expected maximum moment at the reduced section in the capacity-based design of moment-resisting frames. Current design provisions in AISC 358-22 define C𝑝𝑟 as the average of the yield and ultimate strengths of the beam material divided by the yield stress, resulting in a standard value of 1.15 for A992 steel. However, experimental studies have often reported higher values, occasionally exceeding 1.40. This study reevaluates the 𝐶𝑝𝑟 factor using experimental data from 35 existing RBS tests specimens along with finite element analysis results. Back calculated 𝐶𝑝𝑟 values from experiments ranged from 1.06 to 1.44, with an average of 1.21. Variation in 𝐶𝑝𝑟 was attributed to strain hardening, web strength, geometric overstrength, and local/global buckling effects. A new empirical formula is proposed to estimate 𝐶𝑝𝑟 as a function of web slenderness ratio, with an upper bound of 1.45. Underestimation of 𝐶𝑝𝑟 may lead to undesirable behaviors such as panel zone yielding, column kinking, reduced energy dissipation, and potential fracture at beam-to-column welds. Design implications of adopting the proposed 𝐶𝑝𝑟 values include the disqualification of certain beams for shorter bay lengths under the American Institute of Steel Construction guidelines.

Degree

College and Department

Ira A. Fulton College of Engineering

Rights

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