Wednesday, 29 April 2020

Take a more detailed look into the model definition of Pangolin with us

1. Geometry definition

Geometry in Pangolin can be described by lines or circular arcs and polygons made up of the former two.
The relevant components are the simplest ones, acting as converters from the native Grasshopper geometry types, with the possibility of specifying a Consteel Layer.

2. Section definition

The geometry definition of the sections is more refined since Consteel uses detailed section models composed of solid representation for analysis and thin-walled representation for standard design checks. There are two options to create sections in Pangolin: use a predefined section from the section bank or create custom sections by predefined parametric macros.

Predefined sections from section bank

7000+ different profiles can be defined from the section bank (hot-rolled, cold-fromedetc.). This workflow contains two steps:
1. Getting the section preview from the bank.
2. Getting the actual section from the preview. (The reason for this is the performance, as in Pangolin sections are real objects, loading all the 7000+ sections from our bank would take minutes even on a powerful pc.)
The section bank component provides various filtering options, to help select the section. After the desired section preview is selected, you can create a real section from it along with a material, and check the cross-section surface in Rhino.

Custom sections based on predefined macros:

This workflow consists of placing a section macro component, selecting a base macro, and defining the macro parameters.
One of the most important unique features of Consteel is its advanced analysis and design calculations for members with cold-formed sections having various stiffeners. Correspondingly Pangolin makes it possible to create custom cold-formed sections, with custom stiffeners parametrically:
As you can see, the components help in building complex sections with available default values providing a wide range of parameters to be customized.

3. Structural member definition

Defining beams is as easy as pulling the reference edges and the beam section into the Beam component:
In the example above we also defined a haunch on the beam ends, another unique feature of Consteel, which will be taken accurately into account during analysis and design. 
To make modelling easier, Pangolin also provides several useful implicit data conversions, like in the picture above: at the start, we have the IPE 300 beams, and just connecting them into a Grasshopper Plane parameter, the beams get converted to their local coordinate systems. This plane can be directly connected with the Z purlins section direction parameter to correctly lay them upon the main beams.

4. Structural details

Let us stop at the purlins for a moment! Pangolin also provides a detailed linking of structural objects through Consteel’s link elements which can be rather important in order to consider accurately the lateral restraint effect on the beam provided by the purlins.
The definition of link elements includes setting the interface position, the direction, and the stiffness attributes of the connection.
Defining supports for the model is also helped by automatic conversions, where you can directly ask a beam’s endpoint, and place the support there, instead of manipulating with indexes through a complex definition.
Pangolin also provides the possibility to define edge and plate supports.

5. Load definition

Pangolin’s load definition includes load cases, grouped into load groups with specific types like permanent, variable, snow, etc... and custom load combinations. Once the model is sent to Consteel, you can also use its automatic standard-based load combination generator with the groups and cases defined in Grasshopper.
As for the loads themselves, currently, you can define nodal loads, uniform and variable line loads, and uniform and variable plate loads. Additionally, to help place loads on bar members, Pangolin provides a load transfer surface component, which distributes the surface load on (optionally filtered) beams overlapping it.

Variable surface load definition with two points:

6. Using the model for calculations

The model can be calculated by Consteel or Steelspace. Communicating the model with either is done through Pangolin’s Connection component.
This component can accept all Consteel objects and will save a .smadsteel file, and/or send them to Consteel running in the meantime. You can automate either one by defining true for the corresponding parameters.
Additionally, the component will make sure to send everything needed to make the objects valid. Meaning you only have to pull in the beam objects, loads, and supports. The underlying lines, sections, materials, haunches, load cases, support models, and others will be automatically collected by Pangolin for you.

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