A Hysteresis Model for Reinforced Concrete Space Frame Structures

Abstract

224 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993.A hysteresis model to simulate the behavior of reinforced concrete columns subjected to biaxial bending and varying axial load is proposed. The model, identified as the U-model, is based on cross-sectional properties. The U-model combines the Otani's modification of the Clough model and the Ziegler hardening rule of plasticity theory. Other relationships between lateral forces and stiffnesses are also included in the formulation. A change of yielding surface size is used to account for axial load variations.Results of static and dynamic tests were used to investigate the effectiveness of the U-model to simulate the hysteretic behavior of columns. Comparisons between measured and computed responses were satisfactory.The U-model was implemented in simple structural models to study (1) the effect of biaxial interaction during earthquake excitations, and (2) the seismic response of systems susceptible to oscillate around a vertical axis (seismic torsion).Computed results indicated that biaxial interaction does not necessarily lead to larger responses. Its effect, however, can lead to errors of approximately 40% as compared with those computed by neglecting interaction.Results from parametric studies of structural systems with eccentricities show that: (1) As in the case of symmetrical systems, the computed response using two earthquake components was larger than that computed using only one component. (2) Eccentricity in the system increased the biaxial interaction effect slightly. (3) Structural elements of frame systems, proportioned according to typical code torsional provisions, did not experience larger ductility demands than those of equivalent symmetrical systems; (4) Typical code coefficients associated with the accidental eccentricity, used to estimate the design eccentricity, had a small effect on the response maxima of systems with large eccentricities.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD