Modelling of macroelements in STKO

[StavrosP]

Hello,

I am interested in modeling the configuration depicted below in STKO. Specifically, I want some help modeling the embedded part of the foundation with spring stiffness (and damping) consistent matrices, allowing for cross-coupling elements (K_LR in the figure below from Arany et al., 2016). What is the best modeling strategy in terms of elements available in the library?

Thank you in advance,
Stavros

[STKO Team]

The only spring element that can have cross-coupling terms is the 2-node link. However, you cannot explicitly put the cross-coupling term, as it depends on the translational stiffness and the element length
Here is an example:

CrossCouplingLink.zip

(77.23 KiB) Downloaded 203 times

First keep in mind it works in local coordinates.
If you make it vertical, the Kv stiffness goes into the Dir 1, since the axial direction is the first local direction.
Also, if you make it vertical, only the lateral stiffness KL will be coupled with the rotational stiffness (as you want) because there is not delta_x between the 2 nodes.

Now, keep in mind that the cross-coupling term will be KLR = KL*L/2 (where L is the length of the element).
And KRy will be KLR^2 + KR (i.e. the square of the coupling term + the direct rotational stiffness)

Now you can play with the length and the direct KR to obtain the KRy and KLR that you want