Joint Flexibility Huth, Grummann Formulas

[Kanwarosama]

Hi,
I was working on preloaded flange connections of wind turbine towers, trying to model them in abaqus. I need the axial and the shear stiffnesses of the joint. For the shear its the Huths formula that I am thinking of using. But I dont understand what is the effect of number of bolts on this stiffness. Is the Huth equation for a single bolt, a group of bolts or independent on the number of bolts?

 

[rb1957]

Huth is the stiffness of a single bolt. You can get the stiffness of a bolt group using compliance models (see Niu).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[SWComposites]

Yep, single bolt formula.
To get the overall joint stiffness, you will need to model the joint, with cbush/spring/fastener elements for each fastener, where you input the single fastener stiffness values. Note for a torqued fastener, the axial stiffness is not that for the fastener, but is a function of the flange configuration.