Bolted Connections In Solidworks - Gridshell Joint Exercise

Can Solidworks easily handle a bolted connection?

Or: Practice Working on a Gridshell Joint

Gridshells are generally laid out on the ground, then propped into their final shape by scaffolding (or other means, as will be the subject of next year's capstone project). This means that a gridshell joint needs to be attached on the ground while still allowing rotational and longitudinal freedom of its members, and then locked into place when the final form is attained.

The most common way this is achieved today is through the use of clamped plates that sandwich the gridshell members. They are initially applied loosely to allow the members to flex and slide during the erection of the gridshell, and then clamped more tightly later to lock the gridshell into the correct form.

Modeling this joint in Solidworks is a hurdle this research will eventually have to face, due to the potential effect the joints will have on the structure that cannot be modeled by a simple rigid connection. But doing this in Solidworks requires using a bolted connection, which the author was not sure if Solidworks actually had the capability to handle natively. It turns out Solidworks does have this ability, and it really isn't too terribly hard.

In a Solidworks Simulation (in this case a static simulation set to study the stresses on the clamping plates due to rotating force in the members), the user simply needs to select the drop-down menu under 'Connections Advisor' and select 'Bolt' and follow the setup to select the cylindrical cuts the bolt will go through, and the ends where the head and nut will be. This selection even allows for a set preload, a crucial part of any bolted connection (a preload applies the clamping force and prevents joint separation, allowing the joint to be treated as one rigid member).

Approximation of a Gridshell Joint, Showing Bolted Connections

A real clamped connection on a Gridshell would have additional complexity, such as plate shapes that are more visually appealing, and washers (and even some disk springs) on the bolted connection, that are not modeled here. These can be added later to this model or a new model if this ends up being too far from reality.

With that disclaimer in mind, it was possible to run this model, which yielded the following stress visualization:

Approximation of a Gridshell Joint, Under a Twisting Force on the 'Gridshell Members'

This shows almost no load on the members themselves, and almost all of the load on the plates. While this may or may not resemble a realistic connection (ideally the members should only be transmitting compression forces, as shown in the last post), it does show that the bolts are transmitting load through the clamping force they exert.

I also found out that Solidworks does in fact have a way to treat a member as a beam (including selecting joints), so the next step will be to check that out, and see if it is feasible for use in this project.