The Earthquake Engineering Online Archive

Hysteretic behavior of ductile moment-resisting reinforced concrete frame components

Bertero, Vitelmo V.; Popov, Egor P.

UCB/EERC-75/16, Earthquake Engineering Research Center, University of California, Berkeley, 1975-04, 81 pages (530/B37/1975)

Results obtained from investigating the hysteretic behavior of flexural critical regions subjected to high and low shears, and of interior beam-column subassemblages of reinforced concrete ductile moment-resisting frames, are summarized and evaluated. When the average shear stress at the critical region of a flexural member exceeds a value of 3.5 square root f minute subscript c (psi), with a load reversal exceeding the flexural yielding value, a significant degradation in the energy absorption and energy dissipation capacities occurs. By using an inclined web reinforcement in combination with vertical ties, stable hysteretic behavior was achieved of inelastic rotations up to 0.035 rads. in one sense, and 0.067 rads. during a full load reversal. The hysteretic behavior of interior beam-column subassemblages after a reversal of loads inducing a displacement ductility ratio of 2.5 shows (1) a significant P-delta effect and (2) a drastic drop in strength, and especially in stiffness. This drop is caused by the slippage of the main bars of the beams through the interior joint. To avoid these effects, it is recommended that the reinforcement of the beams be designed and detailed to induce plastic hinge formation away from the column faces. The aseismic design implications of the results obtained are assessed and recommendations for improving present seismic code provisions are offered.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-75-16.pdf (2 MB)