Stability Requirements of Deep Steel Wide-Flange Beam-Columns under Cyclic Loading

Just recently, valuable experimental data that characterized the hysteretic behavior of deep wideflange
steel columns (i.e., column depth, d >16 inches) at full-scale became available. Such
members are typically used in steel moment-resisting frames (MRFs) in North America. In order
to expand the findings of the experimental program, an extensive parametric study is conducted
using a validated continuum finite element (FE) modeling approach. The nonlinear behavior of
more than 40 steel wide-flange cross-sections is investigated. Each steel column is subjected to a
monotonic, a symmetric cyclic, and a collapse-consistent lateral loading protocol coupled with
different levels of constant compressive axial load ratios. Based on the FE results, the cyclic
deterioration in the column flexural strength and stiffness is evaluated. Accordingly, design
recommendations are developed related to the seismic compactness criteria for highly ductile
members such that column axial shortening can be reduced under design basis and lowprobability
of occurrence earthquakes. The range of out-of-plane force demands is also evaluated
for the lateral bracing design of columns in steel MRFs. In that respect, the current AISC
provisions are evaluated. Empirical equations are developed for predicting the out-of-plane force
demands and the plastic hinge length in steel wide flange columns.

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