INSTABILITY OF LONGITUDINAL BARS IN RC COLUMNS

The collapse of reinforced concrete structural elements subjected to compression is linked to the instability of the reinforcement bars. This phenomenon may occur in the longitudinal region between two consecutive hoops, or may involve a number of hoops, deforming them through tension until they fail. A criterion is given which makes it possible to determine the unknown length of the region of longitudinal reinforcement involved, in relation to the geometrical and mechanical characteristics of the column. The critical load is then calculated assuming the configuration of a compressed straight bar with built-in ends, bound on unilateral elastic supports. A comparison with the results obtained experimentally by other authors makes it possible to assess the reduction coefficient to apply to the theoretical values deduced. © 1988 ASCE.