Local axis

[miran]

Hi,

I have soil-pile model with batter piles. I am analyzing the dynamic response of this system and thus using LK boundaries. This works great for the soil and vertical piles, but not for batter piles. The shear and pressure waves from the pile are transmitted to the soil with an angle, and I therefore need to change the local axis of the zero length elements with LK-material.

However, using "local axis" in STKO, I am only able to change the axis vectors in global directions. My question is: Is it possible do define an arbitrary local axis in STKO?

[STKO Team]

Hi Miran,

In STKO you can assign 3 types of local axis:

1. Rectangular: they define a local coordinate system which is constant
2. Cylindrical: they define a local coordinate system whose normal vector points in the outward normal direction of a culinder. It is not constant, and the center of the local axis plays a role.
3. Spherical: they define a local coordinate system whose normal vector points in the outward normal direction of a sphere. It is not constant, and the center of the local axis plays a role.

That being said, I need more information about what you want to do, to understand what would be the better solution. For example, where you want to put the LK boundaries, and how you expect the local axis to be oriented.

[miran]

Hi,

I want to create a LK boundary representing soil (or bed rock) at the pile bottom. Due to the inclination of the pile, the wave propagation in the pile, which is parallel with the local x-axis of the pile, does not coincide with the default local axis of the zero length element.

I need a zero-length element with a local axis such that the z-direction is the same as the x-direction of local axis of the pile.

Also, other suggestions on how to solve this would be appreciated.

local axis2.JPG (30.31 KiB) Viewed 3344 times

[STKO Team]

Ok so in this case you just need to define a rectangular local axis. then you need to first click the center point, then a 2nd point that defines the local X axis, and then a 3rd point that defines the X-Y plane.

In your case, since you want the local-Z to be alligned with the beam axis, you can use the beam bottom as the center, and then 2 points used to define the X-Y plane.

Otherwise, you can input the points by hand typing their coordinates on the input terminal:
1st point = 0 0 0
2nd point = e1x e1y e1z
3rd point = e2x e2y e2z

such that [e1x, e1y, e1z] cross [e2x, e2y, e2z] = beam_axis.

If it is not clear, please send us your SCD file

[miran]

Thank you, it works perfectly!