Large fabric buildings serve many purposes, from events to industrial project site applications. Not all fabric structures are alike, of course. Many people see a fabric building and casually call it a “tent”. Turns out not all fabric buildings are tents. In fact, there are some key differences between types of fabric structures that are vitally important to the application and the users of the structure. Let’s take a look at the structural differences between traditional tents and tension fabric structures.
Differences Between Tents and Tension Membrane Structures
We have discussed the many differences between tent structures and fabric structures that affect how they can be used, where, and how long. Tent structures tend to be best for short term use. Because of their structural design, tents may not be able to handle the stresses of different site conditions. If a shelter or workspace is needed for months or years, then a tent may be inappropriate for that application. Because of their highly engineered structural integrity and durable materials, tension fabric membrane systems are better suited to a demanding long-term demanding situation.
When selecting the appropriate product, both the client and the vendor should carefully assess the situation and make sure they have the right structure for their needs. Here are some features to look for.
Structural Differences between Tents and Tensile Architecture Fabric Buildings
Tents and TFS structures may seem to have similar designs at first glance. However, here are some key differences.
- Horizontal Tensioning – A Tension Fabric Structure (TFS) uses horizontal tensioning to create a structure with integrity similar to that of a traditional steel and concrete building. With horizontal tensioning, fabric is fed into the aluminum beams of the frame. A hydraulic ram using 10,000lbs of pressure tensions the fabric while the horizontal frame locks the arches into place. This process incorporates the strength of our PVC coated polyester fabric into the overall strength of the structure, not just using the material as a cover as is the normal use of fabric in a tent. In contrast, tents do not horizontally tension or use the fabric to enhance the strength of the design.
- Extruded Aluminum Beam – Both structures may use this feature, but The TFS has larger beams when compared to a similarly sized tent, making the TFS stronger. The tension fabric building generally will have larger bolts, cross sections, cables, etc. which provide a sturdy frame over which the fabric is tensioned for added strength and resistance.
- Bolted Connections – Tension membrane structures use bolted connections to attach the building’s frame components together, locking them securely in place. A tent system uses hinged connections to secure the structure. Hinged connections create a looser frame that is weaker, rattles in the wind, and is prone to leaking.
- Curved vs. Straight Legs – A TFS uses legs which add additional strength to the design and eliminates the horizontal eave present in straight leg tents. Curved supports and the bowed profile they provide also help the TFS to resist wind and rain and improve snowshed.
Fabric Structure Engineering and Design Make a Difference
How does a tent hold up in strong winds? Some tent vendors have put out engineering reports stating their tent can meet 100 mph wind loads. However, tents are not engineered for the long-term stresses of multiple weather events and may not be able to consistently meet such standards for long periods.
Engineering for Strength and Durability
The engineering of tension fabric structures grants them more durability than tent structures. One key engineering factor is MRI, or mean recurrence interval, which calculates the wind load a building can withstand over a given period of time. If the structure is needed for only a few days, the chance of a difficult weather event occurring is much lower. In that case, the possibility of weather-related structural failure and accompanying risk and safety issues are greatly reduced. This is how a tent company can say it meets high wind loads comparable to a fabric structure. However, over a longer period of time, the wind load capacity would be greatly reduced.
Other key factors are occupancy(what the building is being used for) and category(what type of setting the building is located in).
Generic or Custom Project Engineering
Tents are rented out repeatedly by event companies, so the engineering typically consists of a generic configuration and installation package that fits general use for a few days. This generic engineering approach means a tent can fail if stressed outside that situation, such as a storm event.
In contrast, tensile membrane engineering packages are compiled specifically to meet the site and use requirements of each project, including building codes, MRI, occupancy, and category. The TFS is designed and installed to withstand the stresses of the site and local weather for its duration.
How to Know if it’s a Tent or a Tension Fabric Structure
What are ways a customer can determine if a rental structure is a tent?
- Check the engineering report from your temporary structure rental company. Look for the MRI to see how durable their structures are for bad weather. Then check to see if the report package is designed specifically for your project, adjusting for such things as intended use and location. Did your report appear immediately? If so, you probably have a tent. Because it incorporates a detailed project and site review, the configuration and installation plan of a TFS requires a typical lead time of a week to design a project-specific package.
- Another indicator is where your structure comes from. Tension fabric structures are only serviced by a few expert companies that will deliver their highly engineered structure components across state lines. Tent companies, by contrast, are in every major city, storing their structures in local warehouses. If you can find a comparable product in a nearby major city, you most likely have a tent.
- Check the frame size and bolt type used to connect it and see how they compare. Are they using an extrusion? What size and how many stakes are they using to anchor the tent? Do they talk about uplift resistance, pull tests, or use a dynamometer to measure uplift?
- Do they use horizontal tensioning (described above) on their structure or just downward (vertical) tension? This is a key differentiator, as few tents use this type.
- What kind of equipment do they use to do the install? Some tents are built with small forklifts and scissor lifts, while tension structures use heavy duty equipment. This might include a 10k reach forklift, a 60’ manlift, or even a 60 ton crane for larger applications. Most tent installations are done on the ground with unskilled labor, while a good portion of the TFS installation is done in the air in manlifts with skilled installment workers and equipment operators.
Do you Need a Tent or a Fabric Structure?
Before you shop for a temporary structure, make sure you have a clear understanding of what your need is.
A tent structure rental will do for your application if it:
- Is only for a few days or a week.
- Involves smaller events: weddings, festivals, golf tournaments, short term light storage.
- Occurs while the weather is expected to be good: no strong winds, rain or snow.
- Is on a site that is flat and even, with a surface that can be easily staked.
- Will not include heavy-duty equipment or other activities that could put the structure in danger.
A fabric tension system is more suitable if the structure:
- Is built for a longer duration, months or years
- Is for heavy duty activities such as construction, aviation, mining, site remediation, warehousing
- Must function in severe weather: snow, ice, wind, rain, extreme heat or cold.
- Meet building permit requirements whereas most tents cannot (Permitted Sites)
- Needs a high peak height for operating equipment, additional storage, greater interior volume, etc.
- Needs its weight to be supported by the frame and uses truss systems, fall arrest systems, etc.
For more information on the characteristics and advantages of fabric membrane systems, contact us and speak to one of Allsite’s fabric structure experts. We’ll be happy to help you find the perfect solution for your fabric building needs.