Date of Award

Fall 1993

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering - (Ph.D.)

Department

Civil and Environmental Engineering

First Advisor

C.T. Thomas Hsu

Second Advisor

Farhad Ansari

Third Advisor

Methi Wecharatana

Fourth Advisor

John R. Schuring

Fifth Advisor

Benedict C. Sun

Abstract

A rational analysis of reinforced concrete (R/C) structures requires satisfactory modeling of the behavior of concrete under general loading patterns. The behavioral characteristics of concrete dominantly depends upon its load history. For the study of concrete behavior, parametric study and experimental investigation into the behavior of concrete under load history of random cycles are performed. Through parametric study, the applicability of the previous concrete models is examined and a physically motivated modeling for the cyclic stress-strain relationships is proposed. The present modeling of concrete under general cyclic loading is initiated to provide substantial applicability, flexibility of mathematical expressions and furthermore to describe the behavior of random cycles. For the experimental study of concrete subjected to cyclic axial compressions, tests of 3 in. by 6 in. concrete cylinders are conducted under four different loading regimes to determine the major experimental parameters for the proposed analytical expressions. The model developed is based on the results of parametric study and experimental data obtained for the present study. The validity of the proposed general cyclic model is confirmed through a comparison of the experimental results and simulated behavior of the model. Furthermore, the analytical model proposed has been idealized and incorporated into the procedures in analyzing RIC columns.

The behavior of R/C columns having various properties and subjected to a variety of loading conditions have been the topics of considerable investigation. Of particular significance in the area of unexplored problems is the behavior of R/C columns under cyclic compressive load. It should be noted that cyclic loads with bidirectional eccentricities considered are in the longitudinal direction, and not in the transverse direction, with respect to the column axis. For the experimental investigation, tests of four foot long columns are conducted under stroke control to achieve both ascending and descending branches of the load-deformation curves.

Analysis of RC columns subjected to cyclic axial compressions with bidirectional eccentricities should be approached from the standpoint of a three dimensional problem. A numerical procedure based on extended finite segment method is proposed here to predict the ultimate load, deflections and moment-curvature of experimental results. It is found that the proposed numerical analysis can reasonably simulate the loading and unloading behavior of R/C columns under combined biaxial bending moments and axial compressions.

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