An Approximate Algorithm for Calculating Composite Fundamental Frequency of Single Column Pier with Cast-In-Situ Bored Pile Foundation Based on Frequency Synthesis Method

Based on the frequency synthesis method, the composite fundamental frequency can be expressed to synthetic frequency of each subsystem consisting of inertia component and deformable component, then an approximate algorithm for calculating composite fundamental frequency of single column pier with cast-in-situ bored pile foundation was obtained. Further, the result derived from the algorithm was compared with FEM result and measured value, and the impact in pier´s composite fundamental frequency with different parameters was also studied, which verified the algorithm had clear definition, simple calculation and high precision. The result also indicated that pier´s composite fundamental frequency increased with increasing bridge restraint stiffness, but it approached a certain value when the restraint increased to a certain degree. The approximate algorithm makes a significant contribution to the theory about dynamic identification for rigidity parameters of cast-in-situ bored pile foundation.