Four‐Spring Element for Cyclic Response of R/C Columns

The cyclic response of reinforced concrete columns subjected to bending and axial load is determined using a hysteretic element consisting of four axial springs. The spring sections consist of steel for tensile forces but steel and concrete for compressive forces. The basic spring properties are determined from the calculated balanced moment for the column using simple relationships. The derivation of these properties is described. The force‐deformation relationship for the springs is controlled by the AQ‐Hyst hysteresis model. The model is unsymmetric to account for differences in the tensile and compressive response of the springs. Amplitude‐dependent softening effects are included in unloading and load reversal stages. The four‐spring element was evaluated based on its performance in reproducing the behavior of several reinforced concrete test specimens that had been studied at the University of Tokyo and the University of California, Berkeley. The four‐spring element appeared to be successful in simulating the overall response as long as the axial force did not exceed the balanced load.