Abstract
The effect of a minor disturbing force on the stability of a structure which already is subjected to a major load near the critical state has been studied and is reported here. The approach taken is to develop physical insight to the problem by analysing representative models. The analysis is further developed on a continuum basis and tests are carried out on a small scale structural model. Two types of disturbing force are considered, that is a step pulse or a rectangular pulse. The dynamic response of a structure subjected to such a disturbing force is obtained by numerical integration using the Runge-Kutta method. The analysis neglects the possibilities of changing mode shape during the transient response. The theory developed was compared with a complementary experimental approach. The transient response of a thin wall column was experimentally studied. Special equipment was developed to permit the monitoring of the dynamic effect during the experimental programme. The results of critical disturbance force predictions are in good agreement with the experimental results.