Simulating Rock Climbing Holds with Altair SimLab

I can remember finishing my exam for Multivariable Calculus at my University, and a classmate of mine said invited me to join his group at a rock climbing gym. After spending the past couple hours doing integrals and derivatives, I was eager to do anything that required movement of something other than a pencil, so I happily agreed! I had previously done a little bit of rock climbing outdoors but had never been to a rock climbing gym. When I arrived, I was blown away by all the unique routes and holds on the different climbing walls (Figure 1), it definitely had a different feel than rock climbing outside. I enjoyed that day with my friends, and since that day nearly 20 years ago, I have actively climbed at rock climbing gyms!

Figure 1: Indoor Rock-Climbing Wall with Various Bouldering Routes

With the upcoming 2024 Paris Olympics, I am therefore very excited to see the rock-climbing events. There will be two medal events for rock-climbing: a standalone speed climbing event and a combined event which includes bouldering and lead climbing. With both medal events, it involves climbers pushing themselves to the limits and being dynamic and moving as efficiently through rock climbing holds. It will not be uncommon if you watch these events, to see climbers jump from one hold to the other (Figure 2). One of the things climbers probably neglect thinking about, but is critical, is the stability and durability of the holds they grab onto. The big thing is these holds must be designed to not fail under dynamic and static loading. I decided I wanted to test this, and with the power of Altair SimLab I am going to simulate an example of forces a rock climbing hold may encounter in any of the events at the Paris Olympics in today’s blog!

Figure 2: Rock Climber Bouldering on a Wall

How to Create our Rock-Climbing Hold?

Our first step before we even run our simulation is we need to create a model of a rock climbing hold. If you look at the different types of holds for the upcoming Olympic climbing events, the climbing holds will consist of the following type of holds: jugs, crimps, slopers, pinches, and pockets (Figure 3). I am going to focus on simulating the forces on a jug hold, a jug hold allows a climber to usually place their entire hand on the hold. The jug hold in effect acts as a handle, so a climber can easily slide their hand onto the hold. It is also important to note that jugs can be in a variety of sizes, but I will be modeling one with dimensions approximately of 4 x 3 x 2 inches, just enough space to put about one hand on the jug hold.

Figure 3: Different Types of Rock-Climbing Holds

With Altair Inspire, I can leverage its CAD capabilities to model my jug hold. Inspire has integrated spline tools, so I can create the overhang on my jug hold through creating a spline and moving the spline points to create the desired curvature. Like I mentioned previously, I am going for a 4 x 3 x 2 size jug. You can see a cross section of the dimensions in Figure 4. After creating the spline profile, I can extrude my part and then create any additional fillets and clean up any additional geometry to create the final geometry (Figure 4). With Inspires easy to utilize sketching and geometry modeling capabilities, I can easily create the jug hold in a fraction of the time.

Figure 4: Left (Sketching Dimensions of Jug Hold), Right (Final 3D model of Jug Hold)

Meshing our Model in SimLab

With the model created in Altair Inspire, I can save out the Parasolid file and import it into Altair SimLab. The beauty of using SimLab is it allows me to analyze this model both statically as well as dynamically, since the static and dynamic solvers are accessible in Altair SimLab. Additionally, with SimLabs advanced meshing capabilities, I can assign an adequate mesh in a reasonable amount of time.

In my case my first step will be to generate the mesh. I will assign an adequate mesh size to ensure optimum mesh quality in my system (Figure 5). Note, users can easily check mesh quality in SimLab through clicking on the quality check icon. I then run a failure check, and everywhere in my model meets an acceptable mesh quality criteria.

Figure 5: Meshed Jug Hold Quality Check in Altair-SimLab

Setting up the Simulation Study

With the model now meshed, we can set up our simulation study. In our case I want to simulate the types of forces a hold may encounter during any of the Olympic climbing events. Typically, the largest force a climbing hold may encounter would be a dyno or dynamic move, where a climber jumps onto a hold. Thus, I need to run a dynamic simulation to simulate the dynamic load profile. With Altair SimLab, I can run this dynamic load case, in addition to also running static load cases if I wanted to.

Our next step will be to apply the material properties on our jug-hold. The Paris Olympic climbing holds will utilize Polyurethane as its material. Polyurethane is utilized exclusively for rock climbing holds because they are easy to manufacture, have relatively good strength properties, and the surface finish is what you would want for rock climbing. Now I am not entirely certain of what specific resin they will use for the Olympics, but a common polyurethane for climbing is resin FSD 275UV. This resin has relatively good strength properties, while being relatively cost-effective. I key in the material properties for polyurethane FSD 275UV, in SimLab under the material icon (Figure 6).

Figure 6: Polyurethane Resin Strength Properties

Our next step is to apply the boundary conditions, the big thing in our case is we want to simulate a dynamic loading event. This event will represent a climber jumping on or off of our jug-hold. In reality, climbers will be all different weights and sizes and have different load profiles, in my case I create a profile that is much larger than what we would expect for the Olympic climbers. I also apply my load profile over the course of a second, again this profile may differ in length of time, but this is adequate to set up our analysis. I applied a 1000 lb. normal force profile and then I adjust the scale factor to adjust what the load will be at during various scenarios of the jump. For instance if you see at .1 the scale factor is .2, this means at that time period a load of 200lb is being applied.

Figure 7: Dynamic Load Profile

In addition to the load profile, I also must apply the restraint which keeps the jug-hold in place. The jug-hold will be restrained on the planar face of my model, and thus I apply a fixed restraint on this face. Now with my final boundary conditions set, I can run my model!

Figure 8: Force (shown in yellow arrows) and Restraint (shown in green arrows) Boundary Conditions

Running and visualizing the Simulation

Running a dynamic simulation versus a traditional static simulation, means the structural solver has to solve at different time steps. As a result of this, dynamic simulation is more computationally exhaustive than a static simulation. However, with SimLab I can leverage additional cores to solve this simulation quicker. In my case I have a 20 core laptop, and I am going to leverage solving this analysis with 16 cores, which still gives me enough cores to do other tasks on my machine (Figure 8). It’s important to note, if I wanted to solve with less cores, I could, it would just take longer to solve.

Figure 9: Setting Number of Cores to Solve SimLab Study

After setting the number of processors, I can run my analysis. After a brief period of time, my analysis finishes and I can visualize results for all the different time steps of my study. In my case I can tell the maximum stress aligns with how I am applying my force and restraining my model. We can clearly tell we have a high stress location where we are applying our hands to grip our hold! I can tell that even with the dynamic forces I am applying, it never reaches a critical limit of failure (Figure 9)! This is good to see, as we don’t want to see our climbers falling off the wall due to faulty equipment. In my case I can see a max stress value of about 3.7ksi, which is less than the yield strength for our material of the jug hold.

Figure 10: Results of Dynamic Load on Jug Hold

Now, while I may never reach it to the Olympic stage for climbing as a middle-aged engineer, I can still revel in enjoying the upcoming competition! I can rest easy that all of these holds meet the strength requirements necessary, through my own simulation. I hope this blog has illustrated the power and ease of use of setting and running simulations in Altair SimLab. If you have any more questions about Altair SimLab or any Altair solution, please reach out to us!