An investigation into the "compression-softening" effect in post-tensioned steel beams

This work describes the results of free vibration testing on an externally axially loaded post-tensioned steel beam with a rectangular hollow section. The natural bending frequencies of the steel beam were determined from its measured dynamic response. The validity of the “compression-softening” effect for the post-tensioned steel beam was tested. The implications of the research are extensive, as currently, there is significant disagreement among researchers about the effect of pre- and post-tensioning loads on the dynamic characteristics of members. The natural bending frequencies were calculated from dynamic test results for each axial load level. Specifically, the frequencies were calculated repeatedly while changing the axial load level and the subsequent changes in the frequencies, with increasing axial load were analyzed to determine if the results were statistically significant. It was proved that “compression softening” theory is valid for post-tensioned steel members.