C2.4 External Loads

Apply external loads at the vertices. (by Lotte)

Objective

We will learn how to form find a cablemesh under external loads.

Procedure

The file is exactly the same as in C2.2 Form Finding with the following modifications:

Apply External Vertex Loads

In the default vertex attributes, we will change the external load in z-direction 'pz' from 0 to -0.1. The minus indicates that to load is oriented downwards (in the opposite z-direction) and the 0.1 is chosen as a rough estimate for a point load of 0.035m thickness and an estimated area of 0.3x0.3m per vertex and a concrete density of 24kN/m3.

....
# set default vertex attributes
dva = {

    ...
    
    'pz': -0.1,           # Z-component of an externally applied load. > NEW!
    
    ...
}
mesh.update_default_vertex_attributes(dva)
....

Visualise External Vertex Loads

external loads pz (scaled by 2)

In order to visualise the external loads more clearly, the arrow is scaled up:

...
draw_loads(mesh, baselayer=baselayer, scale=2)

Always visualise the new geometry in a new layer, so that you can compare the difference.

Comparison to Unloaded Mesh

It can be observed that the mesh sags down quite a bit under the external loads in comparison to its pure uniformly prestressed state.

form-found mesh under external loads vs. form-found mesh in pure prestress (in grey)