Content area
Full Text
Results from 16 tests of reinforced concrete columns subjected to different displacement histories are presented. It is concluded that the drift capacity of a reinforced concrete column depends not only on the properties of the column and the applied axial load, but also on the displacement history. A numerical model to calculate drift capacity as a function of displacement history is presented.
Keywords: cyclic load; displacement; drift; reinforcement; shear; transverse reinforcement.
(ProQuest Information and Learning: ... denotes formulae omitted.)
INTRODUCTION AND RESEARCH SIGNIFICANCE
There is very limited knowledge on the effect of variations in displacement history on lateral response of reinforced concrete columns developing inclined cracks.1 Displacement history does not appear in current analytical models as a variable.2-6 A series of tests was designed to determine whether displacement history affects the drift capacity of reinforced concrete columns subjected to inelastic displacement reversals.7 The salient results from these tests are reported herein. The conclusions inferred from these results are limited to the ranges of the variables considered and to columns that can be characterized as follows: 1) drift cycles occur primarily in the plane defined by one of the principal axes of the cross section; 2) the drift capacity is not less than the drift at yield; 3) the maximum shear exceeds the shear at inclined cracking; 4) the shear capacity for monotonically increasing load is more than the shear at yield; 5) the column core is confined by closed ties; and 6) longitudinal reinforcement does not buckle within the drifts considered.
EXPERIMENTAL PROGRAM
Specimen geometry, test setup, and displacement history
The experimental program included eight test assemblies (Table 1), each of which comprised two individual specimens joined by a center stub (Fig. 1). Each specimen represented a cantilever column under constant axial load and a concentrated transverse load applied at its end. The center stub was intended to act as the base of the cantilever columns. All assemblies were tested with simple supports at their ends. Transverse load was applied through the middle stub. Axial load was applied through external post-tensioning rods. The intentional variables in the experiments were: 1) transverse reinforcement ratio outside the center stub; 2) axial load (constant in each test); and 3) displacement history. Figure 2 shows the dimensions of...