提出了基于振动测试参数预测井架钢结构极限承载力的两种新方法。第一种方法是针对井架钢结构的结构形式和受力特征，将其简化为简支梁，由载荷与振动频率之间的关系，推导出振动频率直接确定极限承载力的简易表达式。该方法简单易行，不需要建立系统的模型。第二种方法是应用一阶搜索优化算法修正动力有限元模型，然后进行线性屈曲、几何非线性和双重非线性分析从而确定井架钢结构的极限承载力，这种方法计算复杂些，但提高了预测准确度。最后利用近似平稳随机激励，对某型号井架钢结构进行了振动参数测试，分别应用这两种方法对极限承载力进行了预测。结果表明这两种基于动力参数的预测值相差不大，均能真实预测井架钢结构的极限承载性能，为复杂承载钢结构的极限承载力预测和安全评估开辟了新途径。

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.