I looked into it for a proposed job. The sails themselves are catenaries and are typically very strong in tension. I doubt these are really designed, but are "this is how we build them".
The supports for the shades are a whole other story. The lateral forces at the ends of the sails will depend on the sag in the structure and the loading on the sail itself. Throw in some odd angles and multiple connection points, then the design becomes incredibly complicated and I am not aware of an analysis program that will do this.
We had them for a while, over the inter- teminal sidewalks at Fort Lauderdale International Airport.
The columns and spreaders holding the peripheral catenary cables were quite sturdy.
The structure was easy to study, since the first hurricane ripped off all the fabric. Apparently there was no budget, or maybe no plan, for replacing the fabric.
Any recommend for the finite element program to analyse the tension membrane due to the wind load so I can get all reactions (mainly lateral tension force ???).
Can be ETABS ?
For what it's worth, I watched a crew assembling one of these things and they used wire tension gages when setting the fabric. Sort of guarantees you can meet your design values.
I seem to recall that in some past thread on a similar topic, it was pointed out that the load on the supporting structure could be assumed to be limited by the strength of the fabric part.
tngv, I've had experience in tensile fabric design (both shade sail ($) and permanent fabric ($$$$) in a previous job. For software, there's mpanel fea (
or you can develop your own forces based on the fabric geometry. For code guidance, refer to ASCE 55. The rest is pretty much up to engineering judgement (eg., amount of pretensioning required, force distribution through fabric, etc.). We did have notes saying shade fabric must be removed before snow fall, or if winds exceed 90 mph. Tensile fabric is permanent, so the forces jump fast based on loading and geometry. There are specialty companies that provide tensile or shade structures.
Biggest issue will be resolving the tension from the fabric to the foundations. Unless you have a supporting frame, be prepared for large columns and even larger foundations (which clients do not like or appreciate). There are specialty firms that special in tensile fabric design. And local officials typically have no idea what they're looking at if they are involved for review. So be prepared to defend your calc's if needed.
This makes me think of Horizontal Life Lines and their anchorage. Its probably more work for you to investigate, but they do have tensioner devices and tension relief devices that would limit the loading on the superstructure if the loads on the canopy exceeded a given force. I know the anchorage points can receive some pretty high loads, depending on geometry.
