Abstract：In order to forecast the ultimate bearing capacity of derrick steel structures, two novel methods are proposed based on kinetic parameters identified from vibration measurement. Aiming at the design feature and force characteristic of derrick steel structures, it is simplified freely supported beam. According to the relations between load and frequency, the expression for ultimate bearing capacity determined by frequency is deduced. This method is easy and feasible and the system model needn’t be built. The first order optimization is used for updating the dynamic model in the second method, and then the linear buckle, nonlinear and double nonlinear analysis are carried out to evaluate the ultimate bearing capacity. This method is more complex, but accuracy. At last, the dynamic test of some type of derrick steel structures is carried out using approximate stationary random motivation. The ultimate bearing capacity is obtained by the two mentioned methods. The results show that the relative error is small, which also indicates that the ultimate bearing capacity can be forecasted accuracy by these two methods. These methods also offer an effective way for the ultimate bearing capacity forecast and safety evaluation for complex load carrying steel structures.
2011, Vol. 30 
