Behavior of Unbraced Reinforced Concrete Frames


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Title: Behavior of Unbraced Reinforced Concrete Frames

Author(s): F. N. Rad and R. W. Furlong

Publication: Journal Proceedings

Volume: 77

Issue: 4

Appears on pages(s): 269-278

Keywords: columns (supports); frames; hinges (structural); lateral pressure; limit design; loads (forces); reinforced concrete; stability; strength; structural analysis; structural design; tests.

Date: 7/1/1980

The behavior of one-story, one-bay portions of multistory reinforced concrete frames under gravity loads plus lateral load was investigated theoretically and experimentally. Five two-column frames, three symmetrical and two unsymmetrical, were tested to failure. Theoretical analysis as well as physical tests indicate that the frames under the action of large gravity loads and lateral load be-come unstable after the formation of two "hinges" at leeward joints, either in the ends of the column or the adjacent beams. Thus, complete moment redistribution enabling the frame to form a panel mechanism under increasing lateral load is preempted by instability. The measured ultimate lateral loads were significantly greater than those predicted by "Building Code Requirements for Reinforced Concrete (ACI 318-77). "