To ensure utmost durability when installing clear span structures, professional installers often perform a stake pull test; but what does this mean exactly?
If you were to ask a group of people for words to describe a temporary tent structure, those unfamiliar with them would likely never think to use the word, durable. We don’t often associate durability and tents, do we? They are tents. They are meant to be temporary. And they are sure to blow away with any sight of wind, right?
Wrong.
Temporary tent structures like the clearspan tent are built to possess a high level of durability for all sorts of conditions. They are meant to be reliable semi-permanent structures. However, no matter how well they are designed, their ability to meet these standards is going to rely on how well the tent is put together.
More specifically, the tent stake pull test.
The Need for Holding Power
When brick and mortar buildings are engineered and constructed, they are done so to meet a certain code. They have to be able to handle certain weather conditions with fire safety parameters in place, and more. A newly constructed building will already have people assume it is a durable, strong structure – one that can be relied on should the weather turn sour.
When it comes to clearspan tents, these are often used for a variety of reasons. Some are more permanent, such as warehouse storage or agricultural facility. Whether you need it for a few hours or a few years, you need to have confidence in its ability to stay put, regardless of the weather.
Holding Power: The Engineered Design of Clear Spans
Clearspan structures, such as Losberger, Order (Anchor), and Hoecker all have engineering behind their design. The numbers are very straightforward in stating that the ground-to-plate securement must meet certain specifications.
Sometimes driving in one stake can have enough holding power to meet these requirements. Other times, you may need more than that one stake. Though, it is important to note that you could have every stake in the ground – or an overabundance of stakes in the ground – and still have just as much holding power as the one.
Using a dynamometer is one way to test the holding power. But, these tools are expensive and not everyone knows how to use them properly. Once you gain experience in putting up tents and an understanding of how they are designed – and the factors involved – you begin to feel confident in your assessment.
The Stake Pull Test: An Overview
While it may look like one is pulling the stake out of the ground (hence its name), that is not the case at all. Using a tool such as a dynamometer for a stake pull test, you are measuring the force it takes to pull the stake out. For those who prefer to know the math, the following equation may be used: F = MA (A is acceleration which is derived by the distance something travels over time.)
The pull test should be done on every stake.
Here’s an example. If you are erected a tent and using a sledgehammer to push the stake into the ground, how far does it move with each impact? In ground that has good holding power, the stake may only move an inch with each swing of the sledgehammer. For very soft dirt or sandy soils, one swing could drive the stake in 6 inches.
See the difference?
You can view holding power as how much earth each stake moves out of its way. When you push the stake in the ground, the earth it moves reciprocates by putting pressure on the stake and, in turn, holding it in place.
Note: If permits need to be formally completed, then it doesn’t matter how much experience you have in putting up tents, you will need to use the dynamometer to get a formal number for the permit. This will vary based on location.
All About the Stakes
Many stake properties come into play when determining holding power and durability once a tent is up. And all of these different properties – as well as the grounding – can have a big impact on holding power.
Common stake properties include:
- Length
- Diameter
- Finish (roughness)
- Shape
Remember when we talked about moving earth when the stake entered the ground – and that ground then putting pressure on the stake to hold it in place? If you want to move more earth, you can increase the diameter of the stake (only up to 35mm due to plate restrictions) and/or increase its length. A word of warning to those who had too much length. This could cause other issues, such as bending. And, as a stake bends, its holding power starts to diminish.
For those thinking of adding texture (such as rebar) to stakes for added grip while in the ground, this doesn’t do as big of a job as you may think. The idea is that once the stake is in the ground (including the texture) the ground will apply pressure back on the stake and filling in the sections of texture – resulting in increased holding power. Unfortunately, because you have already disturbed the area when putting the stake in the ground.
Believe it or not, going for a smooth stake that is ½ inch longer can achieve the same holding power as the one with texture. Maybe even more. Regardless of your stake, a pull test should be completed at each job.
Staking and Anchoring in Concrete
Using anchoring systems in concrete is much easier. You have a known strength and you apply the same principles to concrete as you would to moving earth by using a specific diameter and length to achieve the desired holding power.
Many different tests have been performed over the years to understand the holding power of concrete. There is a consideration of cone breakout, in which a really wide diameter anchor is placed shallowly in the concrete. It actually breaks a cone-shape out of concrete out.
Conclusion
Clearspan tents are designed with the utmost durability and strength in mind, and the stake pull test helps to confirm this. It doesn’t stop in the factoring but is reliant upon the proper staking and its holding power. Next time you construct a tent (or have it done) be sure to measure the level of holding power you have so you can rest easy knowing your tent is going to stand up to the challenge.
