Creep Buckling of Uniaxially Loaded Reinforced Concrete Columns

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Title: Creep Buckling of Uniaxially Loaded Reinforced Concrete Columns

Author(s): N. C. Mickleborough and R. I. Gilbert

Publication: Special Publication

Volume: 129

Issue:

Appears on pages(s): 39-55

Keywords: buckling; columns (supports); creep properties; deflection; reinforced concrete; shrinkage; slenderness ratio; test equipment; tests; Structural Research

Date: 12/1/1991

Abstract:
The first stage of an experimental investigation into the instantaneous and time-dependent behavior of reinforced concrete columns under sustained load is reported. The experimental work described in the paper involves the testing of 15 large-scale columns in compression and uniaxial bending to obtain comprehensive creep deformation data for the prediction of long-term lateral deflection and instability. Information on the range of slenderness ratios and load levels which cause creep instability for rectangular symmetrically reinforced concrete columns is of particular interest. The experimental data is also for use in the development and calibration of a theoretical model for the prediction of creep deflection and buckling under sustained load. The experimental setup used in this investigation and described in the paper is designed for the simultaneous testing of five slender columns, each up to 6 m in length. The loading frame is such that each column may have different length, different cross-sectional dimensions and reinforcement details, and be subjected to different combinations of axial force and bending moment. In the three series of tests presented here, column length, axial force, and initial eccentricity are the major variables. The loading on each column is monitored independently and maintained automatically at a constant preset value throughout each test. A direct comparison of creep effects on column behavior is therefore possible as different loading parameters are varied.