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《动力机器基础设计规范》(下称规范)第5.2.8条规定,当基础为横向框架与纵梁构成空间框架时,可简化为按横向平面框架进行计算,并按附录C进行。该规范未指明这种简化应具备的条件,从理论上讲,这种简化是无根据的。因为空间框架可否简化为平面框架,这不仅与扰力分布情况有关,而且与质量分布和刚度分布有关,特别是与纵梁的刚度有关。可以想见:只有当机器的所有扰力作用在横向框架上,同时纵梁的刚度又相对很弱,此时才有可能将空间框架简化为平面框架进行动力分析。为说明《规范》规定的不合理性,下面通过两个实例加以论证。
Section 5.2.8 of the “Code for Design of the Power Machinery” (hereinafter referred to as the “Code”) stipulates that when the basis is the space frame formed by the transverse frame and the stringer, the calculation can be simplified to horizontal plane frames and is carried out according to Appendix C. The specification does not specify the conditions for this simplification, and in theory the simplification is unfounded. Because the spatial framework can be reduced to a planar frame, it is not only related to the distribution of disturbances, but also to the distribution of mass and stiffness, especially the stiffness of the stringers. It is conceivable that it is only possible to simplify the space frame into a planar frame for dynamic analysis only when all the disturbances of the machine act on the transverse frame and the rigidity of the longitudinal beams is relatively weak. To illustrate the “regulation” of the irrational provisions, the following two examples to demonstrate.