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RE: Load factor for Cooling Tower

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Ashraf,
The only ignorance is to NOT ask the question.  And this is a good question!

ACI 350 is specifically written for environmental structures.

From the Scope section of ACI  350:
"The code portion of this document covers the structural design, materials selection, and construction of environmental engineering concrete structures. Such structures are used for conveying, storing, or treating liquid, wastewater, or other materials, such as solid waste. They include ancillary structures for dams, spillways,and channels.

They are subject to uniquely different loadings, more severe exposure conditions and more restrictive serviceability requirements than normal building structures. Loadings include normal dead and live loads and vibrating equipment or hydrodynamic forces. Exposures include concentrated chemicals, alternate wetting and drying, and freezing and thawing of saturated concrete.

Serviceability requirements include liquid-tightness or gas-tightness. Typical structures include conveyance, storage, and treatment structures. Proper design, materials, and construction of environmental engineering concrete structures are required to produce serviceable concrete that is dense, durable, nearly impermeable, resistant to chemicals, with limited deflections and cracking. Leakage must be controlled to minimize contamination of ground water or the environment, to minimize loss of product or infiltration, and to promote durability.

This code presents new material as well as modified portions of the ACI 318-95 Building Code that are applicable to environmental engineering concrete structures."

From the load factor section of ACI 350 the commentary reads:
"R.9.2.5 ? This section addressees the need to consider loading due to weight of fluid or fluid pressure. Although fluid densities and heights are usually well known, the load factor of 1.7 is used as a part of the concept of environmental durability and long-term serviceability of the structure."

Obviously a cooling tower is NOT an environmental structure. However, if you wish to consider long term serviceability, you should consider using the crack limits and load factors contained in ACI 350. Until the cooling tower people develop a code of their own there is not much guidance.

In your area of the world, you have an issue with sulfates in the water and soil. Sulfates are a major serviceability issue.

Regards,
Harold Sprague





From: "Ashraf, Mohammed (Qatar)" <mohammed.ashraf(--nospam--at)worleyparsons.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: Load factor for Cooling Tower
Date: Mon, 11 Sep 2006 09:23:16 +0300

Dear fellow engineers,

I am designing a cooling tower. I have some doubt regarding the load
factors to be used.

For  fluid load (F), ACI 350-01 says U=1.4D+1.7F. But ASCE-02, says
1.4(D+F). Which load combination to used for cooling tower basin
design?.

Ignorance is regretted.

Thanks in advance,

Regards,

Ashraf


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