Abstract: The concept of equivalent angle is provided for the beam column with minor original bend angles in the paper.It is proved that the sum of all bend angles in a beam column is equal to summation of double equivalent angles.It is derived that equivalent transverse load in every bend angle equals axial load multiplied by the bend angle.In order to simplify supports displacement calculation of steerable bottomhole assembly(BHAs),a system of "equations of three moments" can be obtained by the application of equivalent angle to beam column theory.The mechanical characteristic of double bend angles is analyzed in the paper.The technique ways of enhancing BHAs build rate are clarified,which provides theoretical basis for designing and selecting BHAs and for studying drilling technology.

Key words: drilling stem mechanics, bottomhole assembly, beam column

摘要： 提出了结构弯角的等效角概念,证明了一跨梁柱中所有结构弯角之和与两等效角的和相等,推导了各结构弯角处的等效横向载荷等于轴向力与该结构弯角的乘积.把等效角应用于纵横弯曲法中,得出了求解导向动力钻具力学特性的三弯矩方程组,简化了各支座位移计算表达式,并应用于同向双弯钻具的力学特性分析,阐明了增大钻具造斜能力的技术途径,为该钻具的设计、选择及施工工艺研究提供了理论依据.

关键词: 钻柱力学, 井底钻具组合, 梁柱