Some Aspects of Closed-Loop Controlled Testing of Reinforced Concrete Beams at High Rates


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Title: Some Aspects of Closed-Loop Controlled Testing of Reinforced Concrete Beams at High Rates

Author(s): S. M. Kulkarni and S. P. Shah

Publication: Special Publication

Volume: 143


Appears on pages(s): 123-144

Keywords: beams (supports); ductility; dynamic loads; dynamic tests; earthquake-resistant structures; flexural strength; hydraulic structures; models; reinforced concrete; shear strength; strains; tests; Design

Date: 5/1/1994

Discusses important issues relevant to high-rate closed-loop testing of reinforced concrete beams. To obtain a high rate of loading from a closed-loop machine, special considerations are required in the design as well as operation of the machine. These issues are discussed briefly. Useful insight into behavior of a specimen in a high-rate closed-loop test is provided by some analytical expressions supplied here for single-degree-of-freedom (SDOF) and multiple-degree-of-freedom (MDOF) specimen systems. Advantages of displacement control over load control are apparent from the expressions obtained. Preliminary results of displacement-controlled tests conducted on reinforced concrete beams at low and high rates are reported. The specimen deformation-versus-time curve in these tests indicates that, for this setup, the test machine used in this project can apply an essentially constant velocity. Crack pattern obtained for the beams as well as inspection of load and specimen deformation signals indicate that the manner of loading was quasi-static (that is, free of inertial effects) even for the high-rate case. The load-deflection curve for the high-rate case exhibits a down-sloping portion after a small plateau.