Wind Load on Multiple Cooling Towers

[ibrov]

I am designing common supporting platform (20 ft above ground) for 3 cooling towers (shaped as solid parallelepiped 14 ft width, 48 ft length and 18 ft height) with 9 ft space between them (14 ft 1st tower, 9 ft space, 14 ft 2nd tower, 9 ft space and 14 ft 3rd tower). Should wind load (perpendicular to tower’s length) be applied on all three towers or just on 1st one? How to calculate wind load per ASCE-7? Can force coefficient Cf for solid sign be used? Any comments as well as references would be greatly appreciated.
Thanks
Ibro Vehabovic

 

[dbuzz]

You may find that win at 45-degrees is your worst case

 

[JStephen]

I've run into similar situations, where the code just refers to projected area. Normally, that would be at either of two orthogonal directions. However, in a case where moving slightly away from one of those directions increases the loading dramatically, I think it is prudent to design for that case- either by finding the angle that gives worst-case, or assuming load is applied to each object.

 

[Lutfi]

Keep in mind that cooling towers have air intakes that are not solid either! These intakes can occupy entire both sides of the cooling tower. Some towers may be solid and air intake is from the bottom.

If the intake is on both sides, You will not get hat much wind load because the wind will flow through and comes in contact with the water spray and exits at the top of the cooling tower.

You also want to consider design case where the cooling towers are empty. This will increase the wind uplift.

I would investigate that fact as well.

Regards

 

[AUCE98]

I would typically use the C&C loading for cooling towers and be done with it.

 

[Lutfi]

AUCE98,

Use C&C and be done with it! As engineers, we owe it to our clients and ourselves to do the utmost and due diligence to do things the right way. Supports for cooling towers (especially if they are braced) should not be designed as C&C.

We can be conservative in selecting members that may be stressed up to 70% of their capacity. But not C&C and members stressed to 70%.

I applaud Ibrov for his question because few years back I was faced with the very same situation. I did my research, I asked around and then let my engineering judgment be my last call.

 

[ibrov]

What is C&C?

 

[nwm94]

C&C stands for "components and cladding" as opposed to MWFRS, "Main Wind Force-Resisting System". Definitions are in ASCE7.

 

[blake989]

"components and cladding". It is another section in the ASCE 7 typically used by architectural precast, curtain wall, and window detailers. Have you looked into using open buildings and other structures? I've honestly never used this section, maybe it is just for pavillions and structures of that nature, just curious.