【寻找】bolt shaft单元和bolt spring单元的约束方程？

billbill

吾用adina7.4，用bolt shaft单元或bolt spring单元模拟螺栓，但是程序的帮助文件关于该两种单元介绍的十分简练，特别是约束方程是怎样的不清楚。列位有无使用两种单元，敬请告知。多谢！
关于·bolt shaft单元
“The automatically generated constraint equations can be
applied at either one or two ends of the bolt-shaft element. If
applied at only one end, the bolt-shaft element is allowed to spin”
关于bolt spring单元
“The bolt-spring element is used for the modeling of a
connection between touching, or closely-spaced, shell surfaces.
The bolt-spring element consists of six spring elements and
additional constraint equations. Bolt-spring elements can also be
used to model a connection between a shell surface and ground.”