Behavior of Unbraced Multipanel Concrete Frames


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Title: Behavior of Unbraced Multipanel Concrete Frames

Author(s): J. S. Ford, D. C. Chang, and J. E. Breen

Publication: Journal Proceedings

Volume: 78

Issue: 2

Appears on pages(s): 97-115

Keywords: axial loads; bending moments; columns (supports); concrete panels; deflection; ductility; frames; long columns; reinforced concrete; research; slenderness ratio; strength; stress-strain relationships; structural analysis; tied columns.

Date: 3/1/1981

This paper summarizes the observed behavior of a series of unbraced multipanel concrete frames and compares the behavior with predictions of a nonlinear analysis procedure. These frames had four columns of unequal stiffnesses and were loaded with beam, column, and lateral loads. The objectives of the test series were to study the behavior and redistribution capability of highly indeterminate concrete frames under realistic loading corn bina tions, to assess the applicability and accuracy of current design procedures, and to develop analytical modeling techniques for non-linear analysis of frame behavior. The sequence and number of plastic hinge zones noted govern the stability capacity of a multipanel frame with multiple hinges. In all cases, the frames collapsed after only two to five fully yielded regions developed. This is far less than the eight to twelve hinges necessary for full panel collapse mechanisms. The collapse of most specimens resulted from post-yielding in-plane sway instability. The collapse of one specimen clearly resulted from the deformation capacity of a column being exceeded. Column strains at failure far exceeded the ordinarily assumed values of 0.003 in/in.