carrying capacity;  derrick structure;  Dynamic evaluation

A dynamic evaluation method for determining the buckling load of oil drilling derrick structure is proposed. The basic idea is: firstly, the eigenvalue equation of the derrick structure is used to establish the relationship between the basic natural frequency of the derrick structure and the vertical axial force it bears; Then, the basic natural frequency ω1i corresponding to the various levels of load Ni of the derrick structure is calculated or measured, and the change curve between the basic natural frequency ω21i of the derrick structure and the load Ni can be obtained, and the axial force corresponding to ω21i=0 is the buckling load of the derrick structure. The proposed method can be combined with the non-destructive test of derrick structure to determine the buckling load of derrick structure, which is a practical method for evaluating the bearing capacity of oil drilling derrick structure.