8—21节点块体精化不协调元

本文基于文（２）提出的精化直接刚度法的变分原理，构造了８－２１节点元的精化不协调位移模式，并装入ＳＡＰ５程序中，该单元能通过分片试验数据结果表明：采用精化直接刚度法，可以有效地改装单元特性，使新单元在具原单元的简单、高效、可靠性好的同时，在精度，适应性等方面有大幅度的提高。

Refined direct stiffness method of three dimensional 8 21 node isoparametric element

In carrying out the multi input vibration analysis, the high computational effort made us pay particuler attension to refined direct stiffness method (RDSM) to update the original 3 D element. Based on the generalized variational princiaple, a new non conforming displacemant mode of 8 21 node refined isoparametric element is proposed. The numerical results show that this kind of element can pass the patch test and the element possesses many virtues: it can adjust the rigid/flexible characters of the origined element effectively, makes the proposed element simple, hith efficient and reliable while ensure high accuracy convergency and the suitibility.