TEXTILES.ORG
By Michael Tharpe
Q: What is the holding power of stakes?
A: More than a decade ago, industry leaders met to discuss staking, anchoring and the issues in setting industry standards—standards to address questions like: How much staking is adequate for my tent? How do loose soil and high winds affect their holding power? What is the correct placement of stakes to obtain optimal holding power? How should I drive my stakes—straight down or angled? What size stakes should I be using? How far should my stakes be driven into the ground? What can be done to increase the stakes’ holding power?
These discussions evolved into the IFAI Staking Study, a scientific document that educates new and experienced tent renters on installation theory and the holding power of stakes. The Tent Rental Division (TRD) of IFAI contracted with the University of Illinois at Urbana-Champaign’s civil engineering department to produce the study.
Stake failure primarily occurs in two ways: under tension, which means that the frictional forces between the soil and the stake are insufficient to keep the stake from yielding to pullout forces along its axis; or, most commonly, when the sideways force imposed by the stake against the surrounding soil is greater than the soil can hold back, so the soil yields by bulging above the surface. Therefore, the stake simply pushes the unconfined soil out of its path.
These failures are the result of the ground conditions in which tent stakes must perform. Soil conditions, water table variations, surface variations, manmade disturbances and paved sites all have an effect on a stake’s performance. Also, ground conditions are not static. These factors were taken into consideration in the staking study, which established the pullout capacity for a “baseline” stake and then applied corrective factors for conditions that vary from the baseline case—depth of the stake, fastening height of the out guy, stake inclination (angle), stake diameter, load angle and group staking—all of which have a dramatic effect on the holding power of stakes.
The IFAI Procedural Handbook for the Safe Installation and Maintenance of Tentage and Pullout Capacity of Tent Stakes, vol. 1 and 2, are available to buy at www.ifai.com.