The Engineer hour (or anyone with sufficient physics knowledge)

[KrazyHorse]

Originally posted by Zylka
%95 of the support is anchoring??? HAHAHAHA well down the toilet goes this scenario design. Ah well

You're sure, though? The glass panes are *ing huge. Like up to 250lbs per pane. The structural support is also figured to suffice for a winter load of "3 feet of wet snow"

Regarding wind, I guess I should mention that the 1600ft canopy is broken up into two sections, roughly a third and two thirds respectively. So one 1000ft canopy, one 600ft

Like I said, if you want real plans then go talk to an engineer. But I have a feeling that a lightweight material is not a primary concern here.

Vertical loads of this order are easily handled by a rigid steel structure. Most of that structure is going to be there to hold the damn thing down, not to hold it up.

[Zylka]

<<< Engineer of DESTINY

[Japher]

Apolyton census should be used more to determine such things

[:) Smiley]

If you want to cut down on the structure, your best bet would be to make the surface aerodynamic, porous, or both.

Around where I live in the Bay Area, 30 pounds per square foot is a typical design wind load. Wind is pretty mild around here, though, so other places may be higher.

If you want to cut down on the size of the structural elements, design the thing so all members are in tension and won't have to resist buckling or bending loads.

[Zylka]

Only by taking into account the still present snow loads and upward wind pressure that an ETFE structure would have to bear could a realistic range of structural reduction come into play. Yet with a possible 99% weight reduction of canopy glazing in mind, it can not be argued that the resultant reduction in steel support structure would be negligible in determining cost.

I have to hand that in. *SOB*

[DRoseDARs]

Don't cry for me, ArrrgenTEEnah!

[Mr. Harley]

The Scorpian British airmobile light tank is the opposite, though good example. The aluminum armor is sufficiently lighter per unit volume that you end up with thicker panels for the same protection. It turns out that the less dense, thicker panels are structurally stronger than the steal. This let them eliminate the frame of the tank, creating essentially a unitized body tank, so to speak - further cutting the weight.

You really need to compare the structural rigidity of the structure with glass, and without glass, the differences in the cost of glass and more steel to alternative material and somewhat less steal. You may well find that, since most alternative building materials are more expensive, that the traditional building method is cheaper. You may not - which is why you MUST have an engineer so you can calculate the numbers. No numbers means you have opinions, versus facts.

[Kuciwalker]

Originally posted by Zylka
You're sure, though? The glass panes are *ing huge. Like up to 250lbs per pane.

Then they also have a huge surface area and will catch the wind easily.

[The Mad Viking]

Zylka

1. There are two types of loads to consider. Live load and dead load. For your canopy, live load includes wind and snow. Dead load is the glazing system, whether it is glass or mystery stuff.

2. Dead load almost always a small portion of the overall load. In your system, the glass glazing might weigh 6 psf (1/2" tempered single glass) and your system. Your snow load will likely be at least 30 psf. Your uplift wind load will be at least 20 psf sustained load.

In some circumstances, the reduced weight of glazing could make the steel structure MORE EXPENSIVE, if you are in an area where uplift load is more severe than snow load!

3. The (concrete) foundations are what actually anchor the canopy. The steel structure transfers the loads from the glazing to the foundations.

4. For structures supporting glazing systems, deflection is usually the governing criteria. That is stiffness is usually more important than strength. This makes limiting the span of the steel members, and maximizing their stiffness more important considerations than the load.

5. Depending on the snow load vs. wind uplift, there is a chance your mystery material might achieve about a 10% savings in steel mass. Which will likely relate to about 3 or 4 % on the cost of the steel. You could also save about 10% on your foundation cost.

Or, as I said before, your structure costs could go UP! It really depends on your design criteria for the given location.